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How Much Propane A Whole House Generator Uses (Monthly & Yearly)

    If you’re plagued by frequent power outages, you’ll no doubt at least be considering investing in a whole house generator to cut in and shoulder the electrical burden when the power goes out.

    But these backups don’t run on thin air. Unless they’re plumbed into a natural gas line, you’ll need to keep them primed and ready for action with a nearby propane tank.

    How Much Propane A Whole House Generator Uses (Monthly & Yearly)

    This of course means, you’ve guessed it… more expense, so it’s only wise you’re wondering how much propane a whole house generator will burn through on a monthly and annual basis.

    As the answer to your question is determined by a number of factors, I can’t give you a quick answer here, but what I can do is give you some averages and take you through said factors so you can make some informed estimations.

    How Much Propane Will A Whole House Generator Use On Average?

    Generally speaking, you can expect a whole house standby generator to consume roughly 2–3 gallons of propane per hour’s runtime.

    So, for argument’s sake, let’s say that you run your generator for 40 hours every month of the year. That works out as 80–120 gallons a month and between 960–1440 gallons a year.

    Now let’s discuss why these figures are likely not going to be all that relevant to you specifically.

    Whole House Generators: Factors That Impact Propane Consumption


    Propane may be more affordable than gas for the most part, but it’s far from free.

    The more you burn through, the more you’ll have to purchase to keep that whole house generator of yours up and running.

    So, the first variable I put to you is your budgetary boundaries. You can only spend a finite amount on propane throughout the year, so, in effect, you’re capped at a certain volume.

    This will likely lead to a more conservative use of your generator and perhaps a lower propane consumption overall.

    Maybe the best way to ascertain how much people are able to spend on running their generators is to assess how much we spend on electricity bills on a monthly and annual basis.

    On average, an American household will fork out $117.65 per month for electricity, equating to an annual bill of $1411.8.

    Now, given the current average price of propane ($2.30 p/gallon) remains stable, with that same amount of money you’re paying for grid power, you could purchase 613.82 gallons, which breaks down to 51.15 gallons each month.

    Square Footage Of Your Home: Load

    Generally speaking, the larger the home, the more people living in it, and the greater the energy requirements to keep the lights on, the washer washing, the TV televising, etc.

    Heating and cooling systems account for most of the expense in any home, but thermal control can be extremely costly in a larger space.

    It’s thought that you need between 30 and 60 BTUs to heat a single square foot of space every hour throughout the coldest months of the year, so, let’s use 45 BTUs as an average to base the following calculations on.

    For a 1000 square foot space, you’ll need 45,000 BTUs, and for a large 5000 square foot space, you’ll need something to the tune of 225,000 BTUs just to stay warm for an hour.

    What does this mean in terms of propane demand?

    Well, every gallon of propane accounts for about 92,000 BTU, so, worst case scenario, if your power went out for three months of winter, you’d need…

    • 1000 square feet = 105.65 gallons
    • 2000 square feet = 2113.04 gallons
    • 5000 square feet = 5,282.61 gallons

    General Energy Requirements

    Everyone uses energy differently, meaning everyone has a unique propane demand.

    Some people use multiple electronics simultaneously, while others are a little more discerning where energy is concerned.

    If you’re only interested in keeping the absolute essentials up and running, you won’t need anywhere near as much propane as someone who wants to continue life completely as normal in the event of a blackout.

    Let’s take a look at some standard household appliances and how much energy they use:

    • Modern television — 120 watts
    • Laptop — 50 watts
    • Microwave — 1100 watts
    • Fridge — 725 watts
    • Toaster — 1400 watts
    • Dehumidifier/humidifier — 785 watts
    • Hairdryer — 1200 watts
    • Washer/dryer —  Roughly 5500 watts
    • Water heater (40 gallon) — 4500 watts

    Together, these appliances combine to form a 15,380-watt load, amounting to 307,600 BTUs per hour. 

    Now, for the sake of argument, let’s say that you’d need to power all these appliances for 10 days of each month.

    That gives you a monthly requirement of 3,076,000 BTUs, and thus, 33.44 gallons of propane.

    Tally that up over a year and you’re looking at 401.28 gallons.

    Generator Efficiency

    Not all generators perform to spec. Sometimes they’re kind of like solar panels in that they may be advertised as, say, 10,000-watt units, when in practice, they top out at 7000 watts.

    This means the hypothetical generator in question is only 70% efficient, meaning you’d need to invest in more propane than you thought to power a certain amount of appliances during a blackout.

    Frequency & Duration Of Power Outages

    Being that you’re only going to be using your generator when grid power gives up on you, to figure out how much propane you’ll need on a monthly and yearly basis, it’s crucial that you make some relatively accurate estimates of how many hours your power will be down.

    The longer you stand to be left in the dark, the greater your propane demand will be.

    Considering that many generators will use somewhere between 2 and 3 gallons of propane an hour, if you’re hoping to keep your house electrified for 200 hours a month, you’ll need between 400 and 600 gallons of propane.

    Over a year, that would be 4800–7200 gallons.

    Final Thoughts

    There’s a lot to consider when trying to figure out how much propane your whole house generator will need, but now you’re aware of all the contributing factors, you should be able to come up with a ballpark figure for both monthly and yearly demand.