What Size Generator Do I Need for My Pet's Equipment? The Arithmetic, and Where It Has to Stop

“What size generator do I need?” is a question about running watts, starting watts and a fuel runway, and this page answers it in exactly those three terms for equipment that keeps an animal alive: the filter, the air pump, the heat source, the fridge holding a medication. It is not a battery question. Watt-hours, charge cycles and which load to shed when the reserve is thin belong to our battery backup and runtime math for pet equipment, and whether a fuel generator is the right category for your household at all belongs to our comparison of the two categories on noise and portability. This page assumes you have already decided on fuel, and it is about the number on the label and the gallons in the can.

Before any of that, one thing has to be said plainly, because everything below is downstream of it. A generator’s size does not change where it may run. If the only way to reach your animal’s equipment is to bring the generator closer to the house, into the garage, onto the porch, under a cover, or into a shed, the correct move is to relocate the animal or the equipment, not the generator. Human life outranks animal welfare on this page and on every page of this site, and carbon monoxide does not distinguish between the two. CPSC’s own sheet reports that more than 80 consumers die each year from CO poisoning caused by portable generators, and a generator manufacturer warns in its own manual that an extension cord run directly into the home increases the risk of carbon monoxide poisoning through any opening it passes through.

So this page runs in order: where the machine goes, what the alarm does, then the arithmetic, then the fuel, then the wiring question that most searches for “generator sizing” are really circling. Every number below is quoted from a document you can open, and where no source publishes a number, the page says so rather than filling the gap.

Placement Is Not a Sizing Variable

The single most-quoted line in this whole subject is a distance, and it is only true carrying its reference point and the clause attached to it. Here is the full bullet from CPSC Publication 468, What to Know About Generators and Carbon Monoxide (CO), printed with the document number CPSC468 0322 at the foot of page two:

“DO operate portable generators outside only, at least 20 feet away from the house, and direct the generator’s exhaust away from the home and other buildings.”

Away from the house. And the exhaust direction is not a separate tip, it is part of the same sentence. A generator sitting the full distance out with its exhaust pointed at a wall has satisfied half of a rule that was written as one thing.

The same sheet states the prohibition twice, once in a warning panel and once as a don’t, and both halves matter:

“NEVER use inside a home or garage, EVEN IF doors and windows are open.”

“Only use OUTSIDE and far away from windows, doors, and vents.”

“DON’T operate a portable generator inside a home, garage, basement, crawlspace, shed or on a porch; and never leave a car running in an attached garage.”

“DON’T use a portable generator near openings to your home including doors, windows or vents.”

Read the prohibition list as written: home, garage, basement, crawlspace, shed, porch. That is CPSC’s list and it is the complete list on that document. A carport, a breezeway, the space under a deck, an open lean-to, a window well: CPSC does not name any of those, and this page will not put words in CPSC’s mouth by adding them. What we will say, in our own voice and labelled as ours, is that each of them is a reasoned application of the same rule. They are places where exhaust cannot leave freely or where it sits next to an opening, and the outside-only instruction plainly contemplates open outdoor air. If you are standing in one of those spaces wondering, treat the wondering as the answer and move.

CPSC also states the headline consequence, which is worth reading once at full strength before it becomes background noise: “Using a generator indoors CAN KILL YOU IN MINUTES. Generator exhaust contains carbon monoxide. This is a poison you cannot see or smell.” And on the same sheet: “More than 80 consumers die each year from CO poisoning caused by portable generators.”

Three Reference Points, One Magnitude, and Why They Are Not Interchangeable

Several federal sources publish the same number against different things, and blending them produces a rule nobody wrote.

Source	What it says	What it measures from
CPSC Publication 468 (CPSC468 0322)	“operate portable generators outside only, at least 20 feet away from the house, and direct the generator’s exhaust away from the home and other buildings”	the house
FEMA V-1008/December 2023, on Ready.gov	“Use generators, camp stoves or charcoal grills outdoors, at least 20 feet away from any building openings like windows, doors or garages”	building openings
Ready.gov, Generator Safety section (page states Last Updated 06/04/2026)	“Generators and fuel should always be used outdoors and at least 20 feet away from windows, doors and attached garages”	windows, doors, attached garages

A house wall and the nearest window are not in the same place. A generator can be well clear of every window and still be close to a blank stretch of wall, and it can be far from the wall it faces while sitting near a soffit vent on the other side of a corner. The only way to honour all three published instructions is to check each one separately against your own house, not to average them into a single distance. Note also that Ready.gov’s version covers the fuel as well as the machine.

One retrieval note, because a gap is not a silence. The CDC publishes a generator fact sheet at cdc.gov titled “When the Power Goes Out, Keep Your Generator Outside,” and cdc.gov returned HTTP 403 to every automated request made while researching this page on August 11, 2026. That is a blocked retrieval, not an absence, and this page therefore quotes no CDC wording. Read CDC’s own sheet directly. What can be reported here is how a manufacturer characterises that guidance in a document that did open: the Westinghouse WGen12000DF manual (121194 Rev07 7/24/23) instructs owners to “Only use OUTSIDE and far away from windows, doors, and vents as recommended by the US Department of Health and Human Services Centers for Disease Control and Prevention.” And the sentence immediately after that one is the part that gets dropped: “Your specific home and/or wind conditions may require additional distance.”

When Your Own Manual Says a Smaller Number

This is where a pet owner reading carefully will hit a real conflict, so it is worth naming rather than smoothing over. The Westinghouse WGen5500 manual (version 07.23.18KD) tells the owner to verify, before starting, that “You have selected a location that is at least 15 feet (4.5 m) away from any building, other equipment or combustible material.” That is a shorter figure than CPSC’s, from a manufacturer, in the manual for a real machine.

The bullet that follows it in that same list is the qualifier, and it changes what the first bullet permits: “If the generator is located close to a building, make sure it is not located near any windows, doors and/or vents.”

The same manual set carries a separate clearance around the machine itself, which is about heat and fire rather than about the house: the WGen12000DF manual instructs owners that “While operating and storing, keep at least five feet of clearance on all sides of the generator, including overhead.” That is a different measurement answering a different hazard, and meeting it does not address exhaust at all.

Two conclusions follow, and neither is a compromise. A shorter figure in a manual is not permission to sit closer than CPSC’s guidance; the manual’s own next line pulls the reader straight back toward openings. And a manual that publishes a clearance figure is telling you the minimum its manufacturer will stand behind, not the distance that is wise beside a house full of animals that cannot leave. Where the two disagree, the greater separation is the one that satisfies both documents, and no reading of either supports going nearer.

The Extension Cord Is Part of the Placement Decision

For pet loads this is the trap, because the equipment is almost always indoors and the generator is required to be outdoors. The cord is how those two facts meet, and a generator manufacturer treats the cord itself as an asphyxiation hazard. From the WGen12000DF manual, under a labelled hazard heading:

“Asphyxiation hazard. Extension cords running directly into the home increase the risk of carbon monoxide poisoning through any openings. If an extension cord running directly into your home is used to power indoor items, there is a risk of carbon monoxide poisoning to people inside the home. Always use battery-powered carbon monoxide detector (s) that meet current UL 2034 safety standards when running the generator. Regularly check the detector (s) battery.”

And immediately after, in the next hazard block on the same page:

“Asphyxiation hazard. When operating the generator with extension cords, make sure the generator is located in an open, outdoor area, far away from occupied spaces with exhaust pointed away.”

So the cord does not buy you a shorter distance. It converts the opening it passes through into part of the problem, which is exactly what CPSC’s don’t about openings is describing. The practical consequence for a household with an aquarium, a brooder or a terrarium is that cord length is a planning number you should know before a storm, measured from a compliant outdoor position to the tank, not discovered in the dark with a cord that is two feet short.

On the cord itself, three published instructions, none of them ours:

• Westinghouse, WGen12000DF manual: “Only use grounded 3-prong extension cords marked for outdoor use that are rated for the electrical load.”
• PGMA, Safety Awareness: “Connect appliances to the generator using heavy-duty extension cords that are specifically designed for outdoor use. Make sure the wattage rating for each cord exceeds the total wattage of all appliances connected to it.” The same passage continues: “Use extension cords that are long enough to allow the generator to be placed outdoors and far away from windows, doors and vents to the home or to other structures that could be occupied.” It also says to check that the whole length is free of cuts or tears, that the plug has all its prongs, and to “follow all cord safety labels including any limits on cord length.”
• PGMA, on the September 12, 2025 backfeeding release: homeowners are “cautioned to use only 30-amp and 50-amp power cords for these purposes, as it can help prevent overheating and electrical hazards when directly powering appliances.”

That last line is PGMA’s, quoted as PGMA’s, and it is not this page restating a gauge rule as general advice. The rating printed on your own cord is the authority for your own cord.

The Alarm Comes Before the Arithmetic

Every page on this site that mentions a generator carries this, and it is not boilerplate here: an animal cannot self-evacuate, cannot open a door, and cannot act on an alarm. The alarm exists for the human who can do all three.

CPSC Publication 468: “DO install battery-operated CO alarms or CO alarms with battery backup outside sleeping areas, and on each floor of your home. Test alarms monthly.”

The bullet directly after that one lists symptoms, and it is important to notice whose symptoms they are: “DO know the symptoms of CO poisoning: headache, dizziness, weakness, nausea, vomiting, sleepiness, and confusion. If CO poisoning is suspected, get outside immediately, then call 911.” Those are the human signs. The veterinary signs in animals, and what to do about them, are covered with their sources on our full carbon monoxide rule set and the veterinary signs to watch for. Do not read a human symptom list as an animal one.

Where the alarms go on your walls is the alarm manufacturer’s instruction, not ours. The portable generator safety facts PGMA prints at the foot of its ANSI/PGMA G300 release say to “Install a battery-operated carbon monoxide alarm in your home, camper or at your campsite, according to manufacturer’s instructions”, and this page publishes no mounting height in its own voice.

For the code layer, cite the current document. Household carbon monoxide alarm requirements now sit inside NFPA 72, National Fire Alarm and Signaling Code, in Chapter 29, the household chapter maintained by NFPA’s Technical Committee on Single- and Multiple-Station Alarms and Household Signaling Systems, whose published first-draft materials for the cycle that produced the current edition carry the carbon monoxide detection sections under that chapter number. NFPA’s own code development page for NFPA 72 listed the current edition as 2025 when it was read on August 11, 2026, with the next edition listed as 2028. Do not cite NFPA 720 for this: NFPA’s own page for that standard states it “was withdrawn at the Annual 2018 revision cycle” and that “NFPA 720 requirements have been incorporated into NFPA 72,” with the Council voting to approve the withdrawal on August 14, 2018. A specification or a shopping list still pointing at NFPA 720 is pointing at a document that no longer exists as a standard.

Step One: The Nameplate List

Now the arithmetic, and it starts on your equipment rather than on a generator’s box.

The method below is a generator manufacturer’s own, quoted from the WGen12000DF manual so that the instruction and its cautions arrive together:

“Make sure the generator can supply enough continuous (running) and surge (starting) watts for the items you will power at the same time. The total power requirements (Volts x Amps = Watts) of all appliances connected must be considered. Appliance and power tool manufacturers usually list rating information near the model or serial number.”

“To determine power requirements: 1. Select the items you will power at the same time. 2. Total the continuous (running) watts of these items. This is the amount of power the generator must produce to keep the items running.”

The WGen5500 manual explains the same conversion in different words, with a worked example of the unit conversion: “Sometimes the device might only be marked with its voltage (i.e. 120 V) and current draw (e.g. 6 Amp or 6 A), in which case the running power demand in Watts can be obtained by multiplying the voltage times the current, e.g. 120 V × 20 A = 2,400 W.”

Read both of those formulas carefully before using either one. Volts times amps gives volt-amps, not watts, except for a purely resistive load such as a heater or a heat mat. For anything with a motor or a compressor, the volt-amp product is an upper bound on real watts, not the watts figure itself, unless the plate or the manual separately publishes a watt rating or a power factor. Using the volt-amp figure in place of an unpublished watt figure makes the total you build here conservative for choosing a generator, since volt-amps is never less than real watts, but it is the wrong figure to carry over to a watt-hour runtime budget such as the one on our battery backup and runtime math for pet equipment page.

The WGen5500 manual’s own example above is also internally inconsistent: it names the device’s current draw as 6 A and then multiplies 20 A to reach the result. The arithmetic shown, 120 V × 20 A = 2,400 W, is correct for 20 A, not for the 6 A the sentence names first. That is the manual’s own printed error, reproduced here exactly as it appears; read the amps and the watts straight off your own equipment’s plate rather than off either figure in that example.

So the job is mechanical, and it is the part almost nobody does before a storm. Walk to each piece of equipment, find the plate or the sticker near the model and serial number, and write down either the watts or the volts and amps. This page publishes no wattage figures for pet equipment on purpose. Draw ranges for common pet loads, and the runtime math that goes with them, live on our battery backup and runtime math for pet equipment; the figure that governs your generator sizing is the one printed on your unit, not a range from any page including ours.

Two cautions that travel with any chart you may find, including the one printed inside a generator manual. The wattage reference chart in the WGen12000DF manual carries its own footnote in the manual itself: “Wattages listed are approximate. Verify actual wattage.” A manufacturer publishing a chart is telling you to check the label anyway. And the WGen5500 manual notes that resistive devices behave differently from motor-driven ones: “Simple resistive 120-Volt AC devices such as incandescent bulbs, toasters, heaters, etc. have no extra power demand when starting, and so their starting power demands are the same as their running power demands.”

That distinction matters for pet equipment specifically. A heat source that is essentially a resistive element behaves one way at startup; anything with a motor or a compressor behaves another. Which category each of your devices falls into is a question for its manufacturer, not for a table on this site.

What Goes On the List, and What Does Not

Write the list as a list of things that run at the same time, because that is the quantity the manufacturer’s method asks for. A device that only runs while you are standing next to it does not belong on the same line as a device that must run all night.

There is one category that does not go on this list at all. If anyone in the household depends on a powered medical device, that device is not an item to be totalled alongside an aquarium heater and ranked against it. The Westinghouse WGen12000DF manual states it as a general safety precaution in its own words: “Never use the generator to power medical support equipment.” Notice what that sentence does and does not say. It reads medical support equipment, with no species named, so if any of your animal’s own equipment is a prescribed medical device, such as a veterinary-prescribed oxygen concentrator or nebulizer, rather than ordinary husbandry equipment like a heat mat or a filter, the same manufacturer prohibition applies to it exactly as it applies to a person’s ventilator or CPAP. That question belongs to that device’s manufacturer and to your veterinarian, not to this worksheet, in the same way the human version belongs to its own manufacturer and clinician. This site will not publish a shed order that includes a human medical device, and it will not tell you that any power source is sufficient for one. Take that question to the device’s manufacturer, to the durable medical equipment supplier who provided it, or to the prescribing clinician, and take it before hurricane season rather than during an outage. Many utilities also maintain a medical baseline or critical-care customer registry; your utility is the place to ask about that.

The same principle applies on the animal side, in the animal’s own direction. If a pet’s equipment is genuinely life-sustaining rather than merely important, the question of what happens when it stops is a veterinary question with a veterinary answer, and it should be asked of your own veterinarian in advance. This page can tell you how to total watts. It cannot tell you how long your animal has.

Step Two: The Surge Total, and Why This Page Publishes No Multiplier

Startup draw is the number that decides whether a generator actually starts your equipment, and it is the number least likely to be printed anywhere.

The WGen5500 manual is unusually candid about this. Devices containing inductive or capacitive elements such as electric motors, it explains, have a momentary extra power demand when starting, “which can be up to seven times the running power demand or more. Manufacturers of such devices rarely publish this starting power demand and so it’s often necessary to estimate it.”

That sentence is the whole problem. The figure that governs your purchase is frequently not published by the people who made the device.

The same manual then offers an estimate, and the framing it uses is part of the quote: “A rule of thumb for devices fitted with an electric motor is to apply a starting power multiplier of 1.2 for small hand-held or portable devices and a value of 3.5 for larger stationary devices.” It illustrates with its own examples, an angle grinder and an air compressor, and both illustrations use the phrase “can be assumed to have a starting power demand of at least” rather than a claim of fact.

Read that as what it is. It is one generator manufacturer’s rule of thumb, published in one manual, presented by its own author as an estimate that exists because the real number is missing. It is not a physical constant, it is not a standard, and it is not this site’s guidance. We are not going to restate a multiplier in our own voice, because the moment a multiplier appears without its hedge it starts being treated as a specification, and the device it is applied to may be nothing like the devices the rule was written around.

For totalling surge, the WGen12000DF manual gives the method:

“Estimate how many surge (starting) watts you will need. Surge wattage is the short burst of power needed to start electric motor-driven tools or appliances such as a circular saw or refrigerator. Because not all motors start at the same time, total surge watts can be estimated by adding only the item(s) with the highest additional surge watts to the total rated watts from step 2.”

Which means the surge total is not the sum of every device’s spike. It is the running total plus the single largest additional spike. The manual’s own printed example runs that arithmetic in full, adding a highest starting figure to a total running figure to reach a total starting figure, and it repeats the footnote underneath: “Wattages listed are approximate. Verify actual wattage.”

The place to get a real number rather than an estimate is the appliance’s own nameplate, where a motor-driven device may publish a locked-rotor figure, or the appliance manufacturer’s technical support line. If you cannot get it, the honest position is that you have an estimate and you should say so to yourself when you buy.

Loading in Order, Not All at Once

There is one more manufacturer instruction that belongs in the sizing conversation, because it changes what “at the same time” means in practice. From the WGen12000DF manual: “The correct and safe way to manage generator power is to sequentially add loads as follows: 1. With nothing connected to the generator, start the engine as described in this manual. 2. Plug in and turn on the first load, preferably the largest load you have. 3. Permit the generator output to stabilize (engine runs smoothly and attached device operates properly). 4. Plug in and turn on the next load. 5. Again, permit the generator to stabilize. 6. Repeat steps 4 and 5 for each additional load.”

The WGen5500 manual makes the same point from the other side, as a notice: “Starting the generator with loads already applied to it could result in damage to any appliance being powered off the generator during the brief start-up period.”

For a pet household this is worth rehearsing once before a storm, in daylight, because the order you plug things in is a decision you will otherwise be making at three in the morning.

Step Three: The Answer Most Pet Households Actually Get

Search results for generator sizing are dominated by whole-home standby units, and for a pet-equipment load the published federal guidance points somewhere else entirely. FEMA’s power outage information sheet, FEMA V-1008/December 2023, tells households: “Install and use your generator safely. Store fuel safely. Plan to prioritize the things you will need to plug in. You may not be able to power all appliances at one time.”

That is the shape of the honest answer for a pet load. Not a house. A list, in priority order, of what runs simultaneously, sized from nameplates, plus the largest single surge on top of it.

This answer is scoped to pet loads only, and it stops being the answer the moment a human medical device is in the household. Repeating the boundary because an answer read in isolation has to carry it: the Westinghouse manual quoted above says never to use the generator to power medical support equipment, and a household with a prescribed powered device needs the manufacturer, the supplier or the clinician to answer that question rather than an article.

The Under-Load Problem, Which Runs the Other Way

Pet loads are small, and the instinct when a purchase feels safety-critical is to buy larger than needed. There is a published reason to check that instinct with the manufacturer first. From the WGen5500 manual, under the heading Power Output and Demand:

“The generator should not be run completely unloaded for extended periods otherwise the engine may be damaged. It is recommended that the generator should always be operated with at least one-third of its rated 120-Volt AC power output.”

That same manual rates the unit at 5500 running watts on a combined 120/240-volt basis, while the one-third recommendation quoted above is scoped explicitly to the rated 120-Volt AC power output, not the combined rating. Which figure the one-third applies to on your own model is a question for that model’s manufacturer, not an assumption to make from the specification table; ask before you compute a working number, then compare whatever figure you get against the total you built in step one. A pet-only list can land well under it either way, and a household that only ever runs pet equipment on a large machine may be sitting below the recommendation every time it starts. That is not a reason to plug in extra appliances to make a number work. It is a reason to ask the manufacturer of whichever unit you are considering whether a pet-sized load sits inside its recommended operating range, and it is one of the honest arguments for a smaller unit, or for a different category of backup power entirely. Our comparison of the two categories on noise and portability covers the category decision, and it is a fair thing to revisit if this section describes your household.

The Rated Number Is a Ceiling Under Conditions

One more thing the box does not tell you. The WGen12000DF manual states: “Maximum wattage and current are subject to and limited by such factors as fuel BTU content, ambient temperature, altitude, engine conditions, etc. Maximum power decreases about 3.5% for each 1,000 feet above sea level, and will also decrease about 1% for each 10°F (6°C) above 60°F (16°C) ambient temperature.”

Two of those variables are exactly the conditions a pet emergency happens in. A heat emergency is hot by definition, and a mountain household is at altitude every day of the year. Those are Westinghouse’s figures for that model; look for the equivalent statement in your own manual rather than assuming your unit derates the same way.

The same manual also shows what dual fuel costs in output. Its specification page lists “Running Watts: 12,000 Gas / 10,800 LPG” and “Peak Watts: 15,000 Gas / 13,500 LPG.” If your storm plan runs on propane because propane stores better, the number you sized against may not be the number you get.

Step Four: The Fuel Runway

This is the part sizing articles skip, and for an animal that needs a continuous load it is the part that decides the outcome. A generator that covers the wattage and runs dry at hour twenty is not a plan.

Fuel consumption is published per model, at a stated load, by that model’s manufacturer, and it does not transfer between machines. Here is what one manufacturer publishes for one model, in the specification table of the WGen5500 manual: a fuel tank capacity of 6.6 gallons, a run time of 20 hours at 25 percent load, and a run time of 15 hours at 50 percent load.

Now the arithmetic, stated out loud so you can see every assumption inside it. Twenty hours is shorter than twenty-four, so on that model, at that stated load, a full day crosses at least one refuelling, and the fuel you need on hand for one day is more than one tankful. That sentence assumes a constant load at that percentage for the whole period, a full tank at hour zero, the ambient temperature and altitude the rating was taken under, and an engine in the condition the rating assumed. Change any one of them and the number moves. It applies to that model and to no other, and it is arithmetic this page is performing on two published figures rather than a rate Westinghouse publishes.

There is a second wrinkle. Twenty-five percent of a unit rated at 5500 running watts is one specific load, and it is almost certainly not the total your own list produced in step one, so the published twenty hours is not a runtime to plan against until you have checked it against what you will actually be running. Whether a lighter load extends the run time on your unit, and by how much, is a question for your manufacturer, and it runs straight into the one-third recommendation above.

And a third: not every manual publishes a runway at all. The WGen12000DF manual lists a 10.5 gallon tank in its specifications and, on a full read on August 11, 2026, no run time figure this page could locate. If your manual is one of those, you do not have a published runway and should say so to yourself rather than estimate one.

One manufacturer feature worth knowing about, with its own limits attached, is a low idle mode. The WGen12000DF manual describes it as minimising fuel consumption, noise and engine wear by lowering engine RPM when loads are off, and then restricts it in a notice: “DO NOT use Low Idle when powering sensitive electronics or large surge loads, such as an air conditioner, electric pump, refrigerator, or when connected to a home transfer switch.” An aquarium pump and a medication fridge are on that list by category. Read your own manual’s version of that restriction before relying on the feature to stretch a tank.

Refuelling, Which Has No Safe Shortcut

You will be refuelling in the dark, probably in weather, probably tired, and probably with an animal on your mind. Every published instruction on this points the same way.

PGMA, Safety Awareness: “Before refueling a generator, turn it off and let it cool down for at least two minutes before removing the fuel cap. Gasoline spilled on hot engine parts could ignite. Never refuel a running portable generator.”

Ready.gov, Generator Safety: “Let the generator cool before refueling. Fuel spilled on hot engine parts can ignite.”

Westinghouse, WGen5500 manual: “Never refuel the generator while the engine is running. Always turn engine off and allow the generator to cool before refueling.” The same manual adds, on the operational side: “Once the generator is started and the engine gets warm, it is not safe to add gasoline to the fuel tank or engine oil to the engine while the engine is running or the engine and muffler are hot.”

Westinghouse, WGen12000DF manual: “Shut down the engine and allow it to cool for two minutes before adding gasoline or oil to the generator.” And: “Never remove the fuel cap when the generator is running. Shut off the engine and allow the unit to cool at least two minutes. Remove the fuel cap slowly to release pressure, keep fuel from escaping around the cap, and to avoid the heat from the muffler igniting fuel vapors. Tighten the fuel cap securely after refueling.”

The consequence for a pet plan is one you should design for rather than discover: the equipment goes off during refuelling, every time. If your animal’s load cannot tolerate a gap, the answer is a second power source for that gap, planned in advance, not a faster refuel.

The Animal Near the Machine, Not Only the Animal in the House

Everything above protects the house and the people in it from the machine’s exhaust. None of it says anything about an animal standing next to the machine itself, and that gap is worth closing before it becomes an emergency of its own, because a yard is exactly where a loose dog or cat goes when the house is dark and someone is outside working on a generator.

The five-foot clearance quoted above is not a carbon monoxide rule. Westinghouse states it as “While operating and storing, keep at least five feet of clearance on all sides of the generator, including overhead.” It is a heat and fire clearance, and it sits in the same manual as the refuelling warnings quoted above. PGMA states: “Gasoline spilled on hot engine parts could ignite.” Westinghouse separately warns that once the engine is warm it is not safe to add fuel while “the engine and muffler are hot.” None of those sentences was written with a dog or a cat in mind, and no source opened for this page connects the machine’s own heat and fuel hazards to an animal in the yard.

This is this page’s own reasoning, not a published protocol, because nobody publishes one: a muffler and an exhaust outlet stay hot well after the engine itself has cooled, and an animal cannot read a warning label or judge a hot surface the way a person can. Keep pets indoors, or leashed and held well outside the generator’s own five-foot clearance, whenever the machine is running or has recently been running. Keep them clear of the exhaust outlet and muffler specifically, not only the body of the machine. And keep fuel containers closed and out of reach during and after refuelling, since a spilled or open container near a hot engine is the hazard PGMA describes for you, and an animal that knocks one over is added to that same hazard rather than exempt from it.

Where the Fuel May Live

PGMA states the storage rule in three sentences that belong together:

“Never store fuel for your generator inside the home. Gasoline, propane, kerosene, and other flammable liquids should be stored outside of living areas in properly-labeled, non-glass safety containers. Do not store any of these substances near a fuel-burning appliance, such as a natural gas water heater in a garage.”

That third sentence rules out the place most households would default to. An attached garage with a gas water heater in it is specifically named.

How much fuel you may keep, in what containers, and where, is set by NFPA 30, the Flammable and Combustible Liquids Code, and by the fire code your jurisdiction has adopted. NFPA’s own code development page describes NFPA 30 as providing “safeguards to reduce the hazards associated with the storage, handling, and use of flammable and combustible liquids,” and notes it is enforceable under OSHA and many state and local regulations. This page publishes no quantity, because the quantity that applies to you is the one your local fire code sets. Your fire department’s fire prevention office will answer that question over the phone, and it is a better call to make in February than in September.

The WGen12000DF manual adds container and proximity rules of its own: “Store fuel in a container approved for gasoline,” and, when storing the generator, store it away from “sparks, open flames, pilot lights, heat, and other sources of ignition,” and “Do not store gas or a LPG/propane tank near furnaces, water heaters, or any other appliances that produce heat or have automatic ignitions.”

Rain, Standing Water, and the Improvisation to Refuse

Storms are wet, and this is where people invent things.

PGMA’s Safety Awareness page addresses it directly, and the clause after the comma is the whole point: “If you must use a generator when it is wet outside, protect the generator from moisture (as described in the owner’s manual) to help avoid the shock/electrocution hazard, but do so without operating the generator indoors or near openings to any building that can be occupied in order to help avoid the CO hazard.” It continues: “Operate the generator on a dry surface where water cannot reach it or puddle or drain under it. Dry your hands, if wet, before touching the generator.”

Note what PGMA did there. It sent you to the owner’s manual for the protection method, and it fenced the answer so that the wet-weather fix cannot become an indoor or near-opening placement. That fence is the sentence people drop.

Your manual may go further than PGMA. The WGen5500 manual states, in a DANGER block: “Never use the generator in a location that is wet or damp. Never expose the generator to rain, snow, water spray or standing water while in use. Protect the generator from all hazardous weather conditions. Moisture or ice can cause a short circuit or other malfunction in the electrical circuit.” Elsewhere in the same manual: “Never operate your generator outdoors during rain, snow or any combination of weather conditions that could lead to moisture collecting on, in or around the generator.” Ready.gov puts it more briefly: “Keep the generator dry and protected from rain or flooding. Touching a wet generator or devices connected to one can cause electrical shock.”

Three practical consequences. Your manual is the authority on whether and how your specific unit may run in wet weather, and a manual that says never means never for that unit. This page publishes no do-it-yourself weather protection, because a homemade cover that traps exhaust converts a shock problem into a carbon monoxide problem. And no canopy, tent, cover or enclosure sold for generators makes a prohibited location acceptable; none of them is endorsed by CPSC, and CPSC’s outside-only instruction contains no exception for a covered generator.

Connecting to the House, and the Automatic-Transfer Point

Most people searching “what size generator” eventually arrive at the wiring question, and this is where the page stops describing and starts routing.

PGMA published a release on September 12, 2025 titled The Dangers of ‘Backfeeding’: Never plug a generator into an outlet. It describes the misconception first: “The misguided thought is a generator plugged into an outlet will power the homeowner’s or business’s entire property or power certain appliances without running extension cords from the appliance to the generator.” Then the consequence: “In actuality, backfeeding is extremely dangerous and presents an electrocution risk to utility workers and neighbors served by the same utility transformer. It also bypasses some of the built-in household circuit protection devices and can cause short circuits and overloads that lead to electrical fires, prompt fluctuating or excessive voltage that can damage appliances and electronics, and damage a property’s wiring and circuit breaker panel.”

The route PGMA names, with the sentence that closes it:

“Homeowners can have their circuit breakers professionally modified with the installation of a transfer switch or interlock device. A transfer switch serves as a connection point that prevents a generator from feeding electricity back into the power lines. Interlock devices, when installed by a qualified electrician, enable homeowners to safely connect their portable generators to their home’s electrical panel while ensuring the main breaker is disengaged. These are the only safe ways to use a portable generator to power an entire residence.”

Transfer switch. Interlock device. Installed by a qualified electrician. That is the entire extent of what this page will say about connecting a generator to house wiring, and the omission is deliberate: there is no procedure here, no sequence, and no description of how the unsafe method works, not even framed as a warning. The people most at risk from that method are utility line workers who are nowhere near your house.

Manufacturers say the same thing in their own manuals. Westinghouse, WGen12000DF: “When this generator is used to supply a building wiring system the generator must be installed by a qualified electrician and connected to a transfer switch as a separately derived system in accordance with NFPA 70, National Electrical Code.” And in a hazard block: “Fire and electrocution hazard. Do not connect to a building’s electrical system unless the generator and transfer switch have been properly installed and the electrical output has been verified by a qualified electrician. The connection must isolate the generator power from utility power and must comply with all applicable laws and electrical codes.” Westinghouse, WGen5500: “Connecting a portable generator to a buildings electrical system must be made in strict compliance with all national and local electrical codes and laws, and be completed by a qualified electrician”, and, separately, “Always have a licensed electrician connect the generator to the utility circuit.”

NFPA 70, the National Electrical Code, is the code those manuals are pointing at; NFPA’s own code development page listed its current edition as 2026 when read on August 11, 2026. Its generator and optional-standby articles are Article 445, Generators, and Article 702, Optional Standby Systems. NFPA publishes the code text for reading at no cost through its Free Access viewer, and its NFPA 70 page links a Free Access view for each edition including 2026; a free NFPA account is required to view it, and only a purchased copy costs money. A training publisher’s free excerpt, drawn from the 2020 edition, also reproduces both article headings if you want a quick look at the scope before you call anyone. The authority for your particular house is a licensed electrician and your local authority having jurisdiction, and their answer outranks anything on this page.

The Part That Matters When Nobody Is Home With the Animals

A permanently installed generator with an automatic transfer switch starts itself. That is the feature people buy it for, and it is genuinely useful when an outage begins while you are at work and there are animals in the house. It is also the configuration in which nobody is present to notice anything going wrong.

CPSC staff studied exactly this class of machine. A staff report dated June 3, 2025 examined carbon monoxide from stationary generators after Hurricane Ida, and CPSC staff wrote to the chair of the NFPA 37 technical committee on July 3, 2025 summarising the findings. The letter states: “At least 105 homes had indoor CO exposures caused by stationary generators.” And: “85 homes had their CO alarm activate; 20 homes did not mention the presence of a CO alarm or a CO alarm activation.” And: “12 homes had one or more residents with CO poisoning symptoms.”

Read those three lines in order and the conclusion assembles itself. Indoor carbon monoxide exposures from automatic, permanently installed generators are documented, not hypothetical, and in the large majority of the documented cases the thing that raised the alarm was an alarm. An animal alone in the house cannot do what those alarms prompted people to do. Automatic starting does not remove the need for a working carbon monoxide alarm, and it does not remove the need for a human being to check on the house.

The letter also explains why the clearance you may have been quoted was never designed for this. “Manufacturers’ installation instructions rely on clearances in NFPA 37 Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines, which addresses the fire hazard these products pose to nearby structures; there is no standard or code that addresses the CO hazard.” NFPA’s own description of NFPA 37 agrees on its purpose: it “establishes criteria for minimizing the hazards of fire related to the installation and operation of stationary combustion engines and stationary gas turbines that are fueled by liquid or gaseous fuels and are used as prime movers for emergency generators, fire pumps, and stand-by and peak power systems.” A fire clearance is not a carbon monoxide clearance.

About That 25-Foot Number You May Have Seen

This figure has circulated in coverage since mid-2025 and it is routinely quoted out of scope, so here it is exactly as it exists.

CPSC staff’s July 3, 2025 letter states: “In addition, staff recommends that the technical committee for NFPA 37 increase the separation distance between the stationary generator and openings into structures from the current 5 feet to at least 25 feet.”

Four qualifiers travel with that sentence and none of them is optional. It concerns stationary generators, not portable ones. It is a recommendation to a technical committee, not an adopted requirement. It is measured from openings into structures, not from the house. And the letter carries a footnote on its own first page: “This letter and the report were prepared by the CPSC staff. They have not been reviewed or approved by, and may not necessarily reflect the views of, the Commission.”

So: 25 feet is not a rule, it is not about your portable generator, and it is not CPSC’s official position. What it is good for is a question to your installer. If you have a standby unit, asking whether its placement was decided on a fire clearance or on a carbon monoxide clearance, and naming this letter while you ask, is a reasonable conversation to have.

If You Are Buying, Ask for the Shut-Off by Name

CPSC Publication 468: “DO ask retailers for a portable generator with a safety feature to shut off automatically when high CO concentrations are present. Some models with CO shut-off also have reduced emissions.”

Two standards sit behind that feature and you can ask for them by designation. ANSI/PGMA G300-2023 is the portable generator safety and performance standard that includes CO shut-off technology; PGMA’s own release states it “received ANSI approval on December 19, 2023” and that “the effective date for compliance to G300-2023 is for generators manufactured on or after January 1, 2025.” UL 2201, Carbon Monoxide (CO) Emission Rate of Portable Generators, Edition 2, is dated January 9, 2018 with a last revision of February 24, 2023 per UL Standards’ own catalogue listing.

And the thing that has to be said in the same breath, because it is the misreading that kills people: CPSC recommends the feature on the same sheet where it says never use inside a home or garage even if doors and windows are open. The shut-off is a backstop for a mistake, not a permission. It does not make a garage, a porch, a shed or a spot near a window acceptable.

What This Page Does Not Know

An honest sizing page has to name its own holes, because a reader filling one of them with a guess is the failure this whole site exists to prevent.

We could not retrieve CDC’s generator guidance. The CDC publishes a generator fact sheet and carbon monoxide pages at cdc.gov, and cdc.gov returned HTTP 403 to every automated request made on August 11, 2026, as did fema.gov’s own pages and stacks.cdc.gov. Those are blocked retrievals, not evidence of absence, and CDC’s guidance is quoted nowhere on this page as a result. Read it yourself at cdc.gov.

No authority we could find publishes generator sizing guidance for pet equipment specifically. Searches on August 11, 2026 across cpsc.gov, cdc.gov, ready.gov, fema.gov, nfpa.org and pgmaonline.com, plus open web searches combining generator sizing with aquarium, pet equipment, veterinary and emergency preparedness terms, returned generator safety guidance and generator sizing method from manufacturers, and returned pet content only from retailers and hobbyist publications. Ready.gov does address pets in the generator context, in one line, and it is a carbon monoxide line rather than a sizing line: “Install working carbon monoxide detectors on every level of your home. Carbon monoxide is a colorless, odorless gas that can kill you, your family and pets.” Two of the domains in that list were returning 403 to automated retrieval at the time, so treat this as what our searching found, not as proof of what does not exist.

We do not publish a starting-watt multiplier. The only multipliers quoted on this page belong to a manufacturer’s manual and arrive framed as a rule of thumb for an estimate. The real figure for your device belongs to your device’s nameplate or its maker.

We do not publish a fuel burn rate. The only fuel figures here are the tank capacity and the run times at stated loads that Westinghouse prints for one model, plus arithmetic performed openly on them with its assumptions listed. Your model’s numbers are in your manual, and some manuals do not carry them.

We do not know how long your animal has without its equipment. That is a veterinary question about a specific animal with a specific condition, and it is the question that actually determines how much redundancy you need. Ask your veterinarian before a season starts, and write the answer down where your generator plan lives.

Four names to route the rest to, and none of them is us: your veterinarian for any animal threshold, any equipment your animal genuinely depends on, and what to do when it stops. A licensed electrician and your local authority having jurisdiction for anything that touches house wiring. Your local fire department’s fire prevention office for how much fuel you may store and where. The manufacturer of the generator, of the alarm, and of every piece of equipment on your list, for every wattage, clearance, runtime and installation figure. The site closes none of these gaps itself.

The Worksheet to Fill In Before the Storm

• Walk the house and write down, for each piece of pet equipment, the watts or the volts and amps printed near the model or serial number. Note whether the device contains a motor or compressor.
• Ask each equipment manufacturer for the starting draw of anything with a motor, and record whether you got a real figure or an estimate.
• Decide which items must run at the same time, and write that list separately from the list of everything you own.
• Total the running watts of the simultaneous list, then add the single largest additional starting figure on top, the way the manufacturer’s method describes.
• Keep any powered human medical device off this worksheet entirely, and get that answer from the device manufacturer, the equipment supplier, or the prescribing clinician instead. Westinghouse’s prohibition names no species: if any of your animal’s own equipment is a prescribed medical device rather than husbandry equipment, take it off this worksheet too and get that answer from its manufacturer and your veterinarian.
• Confirm with your chosen generator’s manufacturer that a pet-sized load sits inside its recommended operating range, since at least one manual recommends running at no less than a third of rated output.
• Find your model’s published run time and the load it is stated at, and note if your manual publishes neither.
• Measure, in daylight, the actual distance from a compliant outdoor generator position to the equipment, and buy an outdoor-rated cord long enough for that distance rather than for a shorter one.
• Plan the gap: the equipment stops while you refuel, every time. Decide in advance what covers that gap.
• Keep pets indoors, or leashed and outside the generator’s own five-foot clearance, whenever it is running or recently was. Keep them clear of the exhaust outlet and muffler, and keep fuel containers closed and out of reach during and after refuelling.
• Call your fire department’s fire prevention office and ask how much fuel you may store, in what containers, and where.
• Install carbon monoxide alarms per CPSC’s instruction and the alarm manufacturer’s own installation directions, and test them monthly.
• If you have a permanently installed generator, ask your installer whether its placement was set by a fire clearance or by a carbon monoxide clearance, and name CPSC staff’s July 3, 2025 letter when you ask.
• Rehearse the sequential load-up once, in daylight, before you need to do it in the dark.

Where to Go Next

This page is the fuel-generator spoke of our pets and power outages hub. The rest of the backup power problem splits three ways.

If you are still choosing a category. Our comparison of the two categories on noise and portability is the decision before this one, and it matters more than most sizing articles admit for a household with a noise-averse animal. Our battery backup and runtime math for pet equipment carries the watt-hour side, which is a different quantity from the running watts on this page.

If the carbon monoxide question is the one you actually came for. Our full carbon monoxide rule set and the veterinary signs to watch for covers what CO does to animals, what the veterinary sources say about it, and what to do if you suspect exposure. That page owns the medical half; this one owns the arithmetic.

If you know what you are powering but not for how long. Our aquarium and reptile guide to an outage and our pet medication refrigeration guide cover the two loads that most often turn an inconvenience into an emergency, and both are worth reading before you decide how much redundancy your list needs.

Then do the one thing that makes all of it work. Walk the house this week with a pen, and write the numbers off the labels. Everything above is arithmetic once you have them, and none of it is possible without them.