TL;DR — What size propane generator do I need for my house?
For many U.S. homes, I would start evaluating a 4–8 kW propane-rated generator for selected essential circuits or around 14–26 kW for managed whole-house standby backup. A small gas-heated house may need less, while an all-electric home with multiple air conditioners or resistance heating may need 30 kW or more. An 18–22 kW propane standby model is often a useful comparison for a roughly 2,000-square-foot home, but square footage cannot determine generator capacity. I size from real running watts, motor-starting surges, the generator’s rated LP output, and the propane tank’s ability to deliver fuel in cold weather. A professional must verify the final load, gas piping and transfer equipment.
Updated: October 28, 2026. U.S. house-size scenarios are illustrative. Manufacturer fuel-use figures are model-specific; verify the current manual and nameplate before buying.
When you ask me, “What size of propane generator do I need to run my house?” I look beyond the size of your home. I want to know whether you use gas or electric heat, how much air conditioning you have, whether you need a well pump, and what you are willing to leave off during a blackout.
I also ask something people forget: can your propane tank and regulator actually feed the generator at full load? A perfectly sized electrical generator can still fail if the gas supply cannot keep up. In this guide, I focus specifically on LP (liquid propane) generator sizing, not the more general comparison in my house generator wattage guide. I will show you common U.S. house sizes, propane-rated generator classes, fuel consumption, a worked example and my own four-gate readiness check.
Propane Generator Size Chart for Common U.S. House Sizes
If you already own a portable unit labeled 9,500 watts, check my 9500 watt generator runtime on propane guide for fuel use by cylinder size, real model comparisons and why starting watts are not propane running watts.
As a useful U.S. benchmark, the Census Bureau reported that the median newly completed single-family house in 2025 had 2,142 square feet of floor space. That is a housing statistic, not a measured power demand. I’ve grouped the following square-footage ranges to help you start planning; they’re not precise national categories or guaranteed generator recommendations.
| Home floor area | LP generator for essentials only | Propane standby to evaluate for broader backup | What can change the answer |
|---|---|---|---|
| 800–1,200 sq. ft. | 3–5 kW LP-rated | 8–14 kW | Window AC vs electric heat; well pump |
| 1,200–1,600 sq. ft. | 4–7 kW LP-rated | 10–18 kW | Gas furnace vs heat pump; dryer |
| 1,600–2,000 sq. ft. | 5–8 kW LP-rated | 14–22 kW | Central AC starting surge |
| 2,000–2,500 sq. ft. | 5–10 kW LP-rated | 18–26 kW | Electric water heater, HVAC and pump |
| 2,500–3,000 sq. ft. | 6–10 kW LP-rated | 20–30 kW | Two cooling zones, extra appliances |
| 3,000–4,000 sq. ft. | 8–12 kW LP-rated | 24–36 kW+ | Multiple HVAC units and high electric loads |
| 4,000+ sq. ft. | Custom essential-load schedule | 30–48 kW+ may be required | Engineered design and load management |
I would read those numbers as starting points for comparing equipment, not sizes to purchase immediately. An essentials-only calculation assumes you intentionally exclude electric dryers, ovens, electric resistance heaters, EV charging and often central AC. The broader-backup column assumes a suitable transfer switch and possibly automatic load management. If you insist on using every electric heating element simultaneously, you can exceed the range even in a small house.
Propane Generator Size Depends More on Heating Than Floor Area
Here is where I see the biggest difference between two otherwise similar American houses. Suppose one 2,000-square-foot house uses propane for its furnace, water heater and range. A second house of identical floor area uses electric resistance heat, electric water heating and an electric oven. The electrical loads are dramatically different, even though the buildings have the same square footage.
A propane furnace normally needs electricity for its blower, ignition and controls, but not an enormous electric resistance heating element. An electric heat pump also uses electricity to heat the house, and some have backup strips that can draw thousands of extra watts in cold weather. I ask the HVAC contractor which stages can run from the generator and whether heat-strip operation will be locked out or otherwise managed.
| Heating / equipment mix | Illustrative house | Backup implication |
|---|---|---|
| Propane or natural-gas furnace; city water | 1,500–2,000 sq. ft. | Smaller electrical demand if AC and large appliances are limited |
| Gas furnace plus central AC and a sump pump | About 2,000 sq. ft. | Motor starting and simultaneous loads become critical |
| Electric heat pump with auxiliary resistance strips | About 2,000 sq. ft. | Backup heating can sharply increase kW requirement |
| Two HVAC systems, electric water heating and an EV charger | 3,000+ sq. ft. | Large standby unit or aggressive automatic load shedding may be needed |
My first homeowner question is therefore not “How many square feet?” It is “Which high-draw appliances are allowed to operate together during an outage?” That one decision may matter more than another thousand square feet of living space.
Step 1: List the Appliances You Actually Want to Power
I divide your equipment into must-have loads, comfort loads and defer-until-grid-returns loads. For example, refrigeration, essential lights, communication equipment and a medically necessary device may be must-haves. One air-conditioning zone or a gas-furnace blower may be important for comfort. Electric clothes drying, EV charging and pool heating can usually wait.
For a first calculation, I use the appliance nameplates and actual measured operating demand when available. Household wattage charts are estimates: an efficient modern refrigerator can draw differently from an older one, and an AC compressor’s startup demand depends on its design.
| Load (example only) | Running power | Motor-starting requirement | My sizing note |
|---|---|---|---|
| Refrigerator | 500 W | 1,500 W total startup | Compressor may start while other loads run |
| Separate freezer | 350 W | 1,000 W total startup | Consider staggered compressor starts |
| Gas-furnace blower | 650 W | 1,700 W total startup | Gas heat still needs electricity |
| Well pump, about 1/2 hp | 900 W | 2,300 W total startup | Check actual pump motor data |
| Central AC, about 3 tons | 3,500 W | 9,500 W total startup | Startup range varies widely; use nameplate |
| LED lights and common electronics | 500 W | About 500 W | Mostly continuous load |
| Electric water heater | 4,500 W | About 4,500 W | Big sustained resistance load |
| EV charger, typical Level 2 setting | 7,200 W | About 7,200 W | Usually a load to shed during backup |
These example loads deliberately mix small essentials and large optional appliances. I would never sum every row blindly and buy that size, because you may not intend to run them all together. Instead, I mark each load as on, off or automatically controlled during an outage.
Step 2: Add Running Watts and Allow for Motor Starting
I total the watts of the equipment that may run simultaneously, then add the largest extra startup demand from a motor. Be careful with the distinction: if a pump’s running demand is 900 W and its startup demand is 2,300 W total, the extra surge is 1,400 W—not 2,300 W on top of the already counted running load. I check whether two motors can start together, which may require more sophisticated modeling or controls.
For planning, I might use a modest buffer for future needs or measurement uncertainty, but I never assume a certain nominal kW rating guarantees a specific compressor will start. Generator surge capability, voltage regulation, motor characteristics and load sequencing must all be checked.
Step 3: Make Sure the Number Is the LP-Rated Number
For a dual-fuel portable generator, I read the propane running watts and propane starting watts rather than using the larger gasoline values on its carton. The same portable unit can be rated differently for the two fuels. For fixed standby units, I check the manufacturer’s maximum continuous LP kW and the model’s gas-supply specifications, not just marketing language such as “powers most homes.”
Some standby models are rated to deliver more electricity on propane than on natural gas. For example, a published 26 kW Generac standby specification lists 26 kW on liquid propane versus 24 kW on natural gas. It would be incorrect to assume that relationship holds for every model or that propane always produces more power than gasoline in portable generators.
Worked Example: Propane Generator for a 2,000-Square-Foot House
Let me show you a realistic illustration, not an actual home survey. You own a 2,000-square-foot house with a gas-fired furnace, central AC, a well pump, refrigerator, freezer, LED lighting and home-office equipment. You agree not to run the electric dryer, oven or EV charger during a blackout. These estimated wattages are for demonstrating the math; your nameplates will differ.
| Selected backup item | Running W | Total starting W | Extra surge beyond running W |
|---|---|---|---|
| Refrigerator | 500 | 1,500 | 1,000 |
| Freezer | 300 | 950 | 650 |
| Gas furnace blower | 600 | 1,600 | 1,000 |
| Well pump | 900 | 2,600 | 1,700 |
| Central AC | 3,600 | 10,000 | 6,400 |
| Lights, Wi-Fi and outlets | 600 | 600 | 0 |
| Total with all listed loads running | 6,500 | — | Largest extra starting surge: 6,400 |
I add 6,500 W running + 6,400 W additional AC starting = 12,900 W for this simplified simultaneous-load situation. Adding an illustrative 20% planning allowance brings the preliminary target to 15,480 W. I would compare an 18 kW LP standby model with the verified compressor-starting requirements and the specific generator’s motor-start capability, while also checking 20–22 kW choices if load sequencing is limited.
Now I change just one assumption: the house has 10,000 W of electric resistance backup heating that must operate during the outage. The continuous load could jump to 16,500 W. With the same extra AC surge and illustrative allowance, the theoretical figure is 27,480 W. In practice, those heating and cooling loads might not run in the same operating mode; a professional should establish their actual controls and mutually exclusive operation. I use the example to show why a heat-strip decision can matter more than house size.
And I would not conclude that any 18 kW generator will start that particular AC without looking at locked-rotor current, starting kVA, available generator surge, and possible load shedding. If you already have a generator that struggles with motor loads, see why a propane generator loses power under load.
Step 4: Verify Propane Consumption at Half Load and Full Load
Propane generator sizing has a second dimension: fuel flow. A manufacturer’s gallons-per-hour table helps estimate how quickly the tank will empty and how much vapor must be available. I use published figures rather than assuming all 22 kW generators use identical amounts.
The table below reflects approximate next-generation Generac air-cooled standby fuel-use specifications available in 2026. It is a model-family example, not a universal value for every generator with the same rated kW. “Half load” means half of each generator’s own nameplate capacity, so the electrical output being compared is different.
| LP-rated standby model | Electrical output at 50% | Propane at 50% load | Propane at 100% load | Fuel per 24h at 50% load |
|---|---|---|---|---|
| 14 kW | 7 kW | 1.76 gal/h | 2.92 gal/h | 42.24 gal |
| 18 kW | 9 kW | 1.65 gal/h | 2.87 gal/h | 39.60 gal |
| 22 kW | 11 kW | 2.45 gal/h | 3.71 gal/h | 58.80 gal |
| 26 kW | 13 kW | 2.05 gal/h | 3.95 gal/h | 49.20 gal |
Don’t be surprised that a 26 kW model can have lower listed half-load fuel use than a 22 kW model in this family. Engine designs and test points differ. That is exactly why I read the manufacturer’s specific performance table rather than applying a homemade “gallons per kilowatt” rule.
Step 5: Check Full-Load Fuel Input in BTU per Hour
Propane contains approximately 91,500 BTU per liquid gallon for easy planning. That is the fuel’s heat energy, not electricity produced at the outlets. To estimate full-load fuel heat input, I multiply the published propane consumption by 91,500. A propane contractor will need the relevant manufacturer gas-flow specifications and all simultaneous propane-appliance demands to size the system properly.
| LP generator example | Propane at full load | Approx. fuel heat input | What this tells me |
|---|---|---|---|
| 14 kW model | 2.92 gal/h | 267,200 BTU/h | Gas system must support full-load supply |
| 18 kW model | 2.87 gal/h | 262,600 BTU/h | Nameplate size alone does not predict fuel use |
| 22 kW model | 3.71 gal/h | 339,500 BTU/h | Tank and piping must support this generator plus other appliances |
| 26 kW model | 3.95 gal/h | 361,400 BTU/h | Check vaporization at low outdoor temperature |
A key detail: I don’t convert those BTU/h numbers directly into generator electrical kW. The heat input includes engine losses. I also don’t size a gas pipe merely by the diameter of the generator’s inlet connection. The run length, allowed pressure drop, fittings, regulator stages, total flow and local codes belong in a professional design. For a closer look at that topic, read what size propane regulator a standby generator needs.
Step 6: Size the Tank for Runtime AND Vaporization
One of the most expensive mistakes is to buy the right generator and connect it to the wrong fuel storage. I think of the tank as doing two jobs: holding enough total gallons to survive the outage, and boiling liquid propane into vapor fast enough to supply the engine at peak demand. The second job becomes harder when the tank is cold or low.
For planning, a nominal 500-gallon tank generally holds up to about 400 liquid gallons at an 80% fill. But the full 400 gallons is not necessarily the amount I should promise as available for the generator: I may need reserve fuel, I may have other propane appliances, and vaporization decreases as the liquid level drops. I would have the propane supplier size the tank for the local design-low temperature and the expected lowest operating fill level.
Here’s my original reserve-first runtime example. Imagine a 22 kW generator running at an assumed constant half-load fuel rate of 2.45 gal/h, supplied by a 500-gallon tank containing 400 gallons at full permitted fill. I deliberately reserve 20% of that stored liquid for operational margin or other gas appliances, leaving 320 gallons as a calculation budget. Dividing 320 by 2.45 yields approximately 131 hours, or 5.4 days. This is a simplified fuel-budget number, not a promise that a tank will vaporize adequately or that the load stays constant.
| Illustrative tank | Liquid at 80% fill | Budget after extra 20% reserve | Hours at 2.45 gal/h | Approx. days |
|---|---|---|---|---|
| 250-gal stationary tank | 200 gal | 160 gal | 65 h | 2.7 days |
| 500-gal stationary tank | 400 gal | 320 gal | 131 h | 5.4 days |
| 1,000-gal stationary tank | 800 gal | 640 gal | 261 h | 10.9 days |
At the same model’s listed full-load fuel rate of 3.71 gal/h, that 320-gallon budget lasts only about 86 hours—roughly 3.6 days. This difference is why I estimate fuel for the actual outage load, not simply the generator nameplate. For more detail, my propane tank sizing and running-cost guide compares cylinder and stationary-tank choices. If you are sizing a portable generator instead, see the separate 100-lb tank runtime guide.
Why Cold Weather Can Change the Generator Decision
At low outdoor temperatures, a propane tank’s ability to produce vapor falls; low liquid level reduces wetted surface area and can reduce vapor delivery further. If the same tank also fuels a furnace, both appliances may call for gas during the coldest part of the outage. The propane contractor must evaluate the combined full-load fuel demand, not merely the generator’s average gallons per hour.
If a generator starts normally but loses gas pressure when the house heating system is running, I would investigate available vaporization and fuel-system design with a qualified professional, not adjust the regulator blindly. I discuss that symptom in why propane pressure drops when a generator starts.
My Four-Gate Propane Readiness Check Before You Buy
Instead of trusting a salesperson’s single recommended number, I use a four-gate worksheet that forces the important decisions into view. I call these Load, Start, Fuel and Duration. It’s my practical organization method, not an official engineering standard. I would only describe a proposal as ready to price after all four gates have answers.
| Gate | Question I ask | Evidence to request |
|---|---|---|
| 1 — LOAD | Can the generator supply the watts my selected circuits actually use together? | Circuit schedule and appliance nameplate ratings |
| 2 — START | Can it start my AC, well pump and other motors without unacceptable voltage dip? | Motor-start data and manufacturer generator surge specifications |
| 3 — FUEL | Can the propane system deliver full-load gas flow at the coldest expected conditions? | Supplier’s vaporization, piping, regulator and pressure assessment |
| 4 — DURATION | How many days of outage can I afford before a refill, with reserve? | Fuel rate at likely load, tank fill, other appliances and reserve |
Here’s the hidden benefit: failing one gate gives me an actionable next step. If LOAD is the problem, I remove or schedule optional appliances. If START is the problem, I investigate compatible soft-start and sequencing options. If FUEL fails, I ask the propane professional about supply capacity. If DURATION fails, I change my tank or usage plan. I don’t blindly buy a bigger generator to solve a fuel or runtime problem.
Portable LP Generator or Whole-House Propane Standby?
I’d choose a portable propane-rated generator for occasional essential-circuit backup when you’re willing to start it manually and restrict the load. For automatic operation, central HVAC and long outages, a fixed standby system with an approved transfer switch can be more convenient. A portable generator must run outside, far away from openings and enclosed spaces, with exhaust directed away from the home. Never backfeed a wall outlet. A licensed electrician should specify the connection method, and the propane supplier should verify any fixed fuel connection.
Whichever type I choose, I plan the maintenance in advance. My propane generator maintenance checklist explains what to inspect and how to log engine hours. I also consider long-term propane generator reliability rather than treating size as the only purchase criterion.
Frequently Asked Questions
Will a 10 kW propane generator run a whole house?
Sometimes, for a small or lightly electrified house with strict load management. I would not promise central AC, electric water heating and a dryer all running together. I calculate running and motor-start demand from the chosen circuits and confirm the propane output rating of that specific generator.
What size propane generator for a 1,500-square-foot home?
I’d compare roughly 4–7 kW LP-rated power for basic essentials and around 10–18 kW for broader standby service, then adjust for heat, AC and pumps. These are examples rather than purchase specifications.
Is 18 kW enough for a 2,000-square-foot house?
It may be for a gas-heated home with sensible load management, but an all-electric property could need much more. I would check AC starting requirements, other motors and simultaneous heating loads before selecting an 18 kW LP unit.
What propane generator size for a 3,000-square-foot house?
I would investigate the 20–30 kW range for managed backup and potentially more for multiple HVAC systems or electric resistance heating. Again, the actual load schedule matters more than the floor area.
Does a 22 kW propane generator need a 500-gallon tank?
Not necessarily. Tank selection depends on the desired outage duration, winter temperatures, liquid level, other propane appliances and the supplier’s vaporization calculation. A 500-gallon tank is a common residential planning option, but neither 22 kW nor 500 gallons automatically guarantees reliable supply.
Can I use a 20-lb propane cylinder for a house generator?
A compatible small portable generator may use a 20-lb cylinder, but its runtime is limited and winter vaporization may be inadequate for heavy demand. I would not assume a household standby unit can operate safely from one barbecue cylinder. See how long a 20-lb propane tank runs a generator for the separate portable-generator question.
Final Recommendation: Size the Electrical Load and the Propane Supply Together
For most homeowners, my starting discussion is about 4–8 kW for essential circuits or 14–26 kW for broader residential standby power, followed by a calculation specific to the house. For a 2,000-square-foot home, I’d compare 18–22 kW LP standby models when central AC is an important load, but I’d also look for opportunities to safely shed optional loads before increasing capacity.
Just as important, I verify that the tank, piping and regulator can supply enough propane at full generator load, even when the weather is cold and the furnace is using fuel too. A generator purchase is complete only when the electrical sizing, motor starting, fuel delivery and desired runtime all agree.
If you’re comparing costs as well as sizing, my gasoline versus propane generator running-cost comparison helps put fuel expense into perspective. I’d rather see you buy the right complete backup system than spend extra on a generator whose available fuel supply or electrical connection cannot support it.
Mike is an experienced propane technician with over 15 years of professional experience in the field. He has dedicated his career to helping customers with their propane needs, from installation to maintenance and repair. Together with Jeremy, he co-founded this website to provide useful information and guidance to customers seeking reliable propane services.
