Nobody can honestly tell you which one is cheaper per hour, because the answer depends on two prices only you have: what a unit of electricity costs you, and what propane costs where you fill up. Here is the conversion that settles it. A gallon of propane holds about 26.8 kilowatt hours worth of energy. So propane is the cheaper fuel for you only if a gallon costs less than about 26.8 times what one kilowatt hour costs you. Check your own electricity bill and your own last propane receipt, do that one multiplication, and you have your answer instead of somebody else's.
That is the whole method. The rest of this page explains where the number comes from, why the two appliances are not even sold in the same units, and what the fuel comparison still cannot tell you.
First, because one of these burns fuel
A propane patio heater is a combustion appliance. It produces carbon monoxide, which is colorless, odorless and gives no warning. Every one of these appliances is labeled for outdoor use only, and that label is a safety instruction rather than a suggestion.
The US Consumer Product Safety Commission warns that gas-fired radiant heaters run in small, poorly ventilated enclosed areas such as a tent or a trailer present a carbon monoxide poisoning hazard that can cause death. The International Fire Code takes the same position in its own language: it prohibits portable outdoor gas-fired heating appliances inside any occupancy while connected to the fuel container, inside tents, canopies and membrane structures, and on exterior balconies.
An electric infrared heater has no combustion and produces no combustion gases at all. That difference does not appear anywhere in a running-cost calculation, and for some patios it decides the purchase before cost is even discussed.
The two appliances are not sold in the same units
This is the reason the comparison goes wrong so often. Electricity is sold by the kilowatt hour, an amount of energy. Propane is sold by the gallon in some places and by the pound in others, and a gallon is a volume while a pound is a weight.
The appliances are rated differently too. An electric patio heater is rated in watts or kilowatts, which is the rate it draws power. A gas patio heater is rated in BTU per hour, which is the rate it consumes fuel energy. Those two ratings are not directly comparable as printed.
So before any money enters the arithmetic, both sides have to be expressed in the same unit of energy. The US Energy Information Administration publishes the conversions that do it: one kilowatt hour equals 3,412 BTU, and one gallon of propane holds 91,452 BTU.
Divide the second by the first and you get the number in the answer above. One gallon of propane carries roughly 26.8 kilowatt hours of energy in it.
The break-even, with your prices instead of ours
We are not going to print an electricity rate or a propane price. Rates differ by country, by region, by supplier and by month, and a propane price printed in September is wrong by Christmas. What does not change is the relationship.
Find one gallon of propane on your last receipt. Find one kilowatt hour on your electricity bill. Multiply the electricity figure by 26.8.
- If the gallon costs less than that product, propane is your cheaper source of raw energy.
- If the gallon costs more, electricity is.
If you buy propane by weight rather than by volume, convert first: a gallon of liquid propane weighs roughly 4.2 pounds, so multiply your price per pound by about 4.2 to get a price per gallon. And a "20 lb tank" describes 20 pounds of fuel, not 20 gallons. Filled to the standard 80 percent safe-fill level it holds a little under five gallons. That single misunderstanding is behind a lot of the confident cost-per-hour figures on page one.
Cost per hour, for your specific heater
Once both sides are in the same unit, the hourly figures are short arithmetic. Take both ratings from the appliance's own data plate, not from the marketing copy, because the plate is what the manufacturer certifies.
| Side | What you need | The hourly calculation |
|---|---|---|
| Electric | The kilowatt rating on the plate, and your price per kWh | kW rating multiplied by your price per kWh |
| Propane | The BTU per hour rating on the plate, and your price per gallon | (BTU per hour rating divided by 91,452) multiplied by your price per gallon |
Two notes that keep the result honest. The propane figure is fuel consumed at full output, so an appliance run on a low setting burns less. And a plate rating is an input rating on both sides; it is not a promise about how much warmth reaches your chair. We took that apart in detail in the piece on how many BTU of patio heater you actually need, and the short version is that the rating measures the appliance's appetite, not your comfort.
Where the fuel comparison stops being fair
The 26.8 rule compares energy in the fuel. It does not compare warmth delivered to a person, and the two sides lose energy differently on the way there.
An electric resistance or infrared element turns essentially all the electricity it draws into heat, right there at the emitter, because there are no combustion gases to carry any of it away. A gas burner's rating is fuel energy going in, and some share of that leaves as hot exhaust rising past the reflector before it can be radiated at anybody. Nobody publishes a defensible figure for that share on patio heaters, and we are not going to invent one, but the direction is not in dispute: it shifts the break-even in electricity's favor by some amount.
Then there is where the heat goes. Both types work mostly by radiation, and radiation travels in straight lines and falls off sharply with distance. A tall freestanding unit spreading a weak cone over a wide circle and a wall-mounted electric panel aimed at two chairs can burn very different amounts of energy to make the same two people comfortable. The number that decides your season is cost per warm seat, not cost per hour, and no spec sheet gives you that one.
The costs that are not fuel
Neither appliance is only its fuel bill, and this is where the honest comparison usually turns.
Propane costs you trips and hardware. You buy or exchange cylinders, you refill them, and the tank runs down fastest on exactly the cold nights you wanted it most. Exchange cylinders are frequently filled to less than a full 20 pounds, so the price you paid does not always buy the fuel you assumed. Against that, propane needs no power at all, which is what makes it the right answer for a seating area with no outdoor circuit anywhere near it. That portability-versus-plumbing trade is the same one we set out in choosing between a propane and a wood burning fire pit.
Electric costs you a circuit. A plug-in unit is only a plug-in unit if the outdoor circuit is rated for it and weather-protected. Larger electric infrared heaters are hardwired, and that is an electrician's job with its own price attached. If the quote for the circuit is more than the heater, the cheaper fuel has just become the more expensive purchase.
This is the same shape as any equipment decision where the running cost and the total cost point in different directions, which is why we work them out separately in things like whether renting or buying a lawn aerator makes more sense.
What actually moves the number more than fuel choice
Three things beat the electric-versus-propane decision outright for total spend across a season.
Hours. An appliance run for two hours on ten evenings costs a fraction of one run all evening every weekend, at any fuel price. Most people badly overestimate how many evenings they will use it.
Wind. Moving air carries convected warmth away and strips heat from skin faster. On a breezy patio you will turn the heater up, leave it on longer, and get less for it. A windbreak that is not an enclosure buys more comfort per unit of fuel than a bigger appliance does.
Placement. Closer to the seats, aimed at the seats. Distance is punishing for radiant heat, and moving a heater two feet closer is free, while buying a bigger one is not. Placement is bounded by the clearances in your manual, which is the same discipline that governs how far a fire pit has to sit from the house.
Where this article stops
Anything involving the gas connection, the hose, the regulator or the cylinder valve goes to the manufacturer's instructions and to a qualified gas professional. Do not modify, extend or repair a gas connection, and do not run a heater with a hose or regulator that is not the one specified for it. A permanently plumbed natural gas heater is licensed gas fitting work everywhere we are aware of.
A hardwired electric heater is a licensed electrician's job, and outdoor circuits carry their own requirements for weatherproof enclosures and ground fault protection.
Clearances, permitted mounting positions and whether any overhead structure is allowed come from your appliance's own manual and your local authority. Not from us, and not from a retailer's buying guide.
Frequently asked questions
Is an electric or propane patio heater cheaper to run? It depends entirely on your two local prices. A gallon of propane holds about 26.8 kilowatt hours worth of energy, from the Energy Information Administration's figures of 91,452 BTU per gallon and 3,412 BTU per kilowatt hour. If a gallon of propane costs you less than 26.8 times the price of one kilowatt hour, propane is the cheaper fuel. If it costs more, electricity is.
How do I work out the cost per hour of my own patio heater? For electric, multiply the kilowatt rating on the data plate by your price per kilowatt hour. For propane, divide the BTU per hour rating on the plate by 91,452 to get gallons per hour, then multiply by your price per gallon. Use the plate rating, not the marketing figure, and remember it describes full output.
Why does every website give a different cost per hour for a patio heater? Because they are each using one energy price, from one country, at one moment, and often for an unstated appliance size. Energy prices move by region and by season, and propane is sold by the gallon in some places and by the pound in others. A cost-per-hour figure is out of date almost immediately and rarely applies where the reader lives.
How many gallons are in a 20 lb propane tank? A 20 lb cylinder is named for the weight of fuel it carries, not a volume. Filled to the standard 80 percent safe-fill level it holds a little under five gallons, because liquid propane weighs roughly 4.2 pounds per gallon. Exchange cylinders are often filled to less than a full 20 pounds, which is worth checking if you are comparing costs.
Does a higher BTU rating mean higher running costs? Yes, at full output, because the BTU per hour rating is the rate at which the appliance consumes fuel energy. It does not follow that the bigger appliance is worse value, because a well-aimed unit close to the seats can be run lower and for less time than a large one placed for symmetry.
Yard Insight has not tested a patio heater, and this article makes no claim otherwise. No energy price, fuel price or cost per hour is stated anywhere above, deliberately: those figures differ by country, region and month, and the method here is designed to work with your own. The energy conversions are the US Energy Information Administration's published figures for propane and electricity. The carbon monoxide guidance is the US Consumer Product Safety Commission's, and the prohibited locations are the International Fire Code's provisions for portable outdoor gas-fired heating appliances. Sources read 2026-09-07. If anyone develops headache, dizziness, nausea or confusion around a fuel-burning heater, get into fresh air and seek medical advice.
