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As an example only, at $3.00 per gallon for propane, a 9,000 BTU Mr. Heater Buddy costs roughly $0.30 per hour to run at full output. Smaller models cost less; larger ones cost more. Your actual number depends on your heater’s BTU rating and your local propane price, which varies by region and season.
The Quick Formula
Since propane holds about 21,600 BTU of usable energy per pound, dividing your heater’s BTU rating by that figure tells you roughly how many pounds it burns in an hour. Converting your local price per gallon into a price per pound, by dividing it by 4.24 (the approximate weight of a gallon of propane), gives you the other half of the equation. Multiplying those two numbers together produces your estimated cost per hour of operation.
Worked Examples Across the Buddy Lineup
Using the same $3.00-per-gallon example price, a 3,800 BTU Little Buddy works out to roughly $0.12 per hour, while a 9,000 BTU Buddy comes to about $0.30 per hour, and an 18,000 BTU Big Buddy climbs to around $0.59 per hour. Notice that cost scales directly with BTU output rather than with whichever tank size happens to be feeding the heater.
Why Tank Size Doesn’t Change the Hourly Cost
Although a 20 lb tank costs considerably more to fill than a 1 lb cylinder, it also holds roughly 20 times as much fuel, so the actual cost of running the heater for an hour ends up being identical either way. What changes with tank size is simply how often you need to refill or swap fuel, not what a given hour of heat actually costs you. Our what size propane tank do I need answer covers choosing between the two options in more detail.
Running at a Lower Setting Costs Less
The examples above assume the heater is running at full output, since that produces the easiest number to calculate from a spec sheet. In practice, many owners run their heater on a lower setting for most of a session, only stepping up to full output when conditions genuinely call for it, and the cost per hour drops roughly in proportion to how far below maximum the heater is actually operating.
Why We Don’t Quote a Single National Price
Because propane price per gallon varies considerably by region, by season, and by whether you’re refilling your own tank versus exchanging one at a retailer, a number that looks accurate today can become noticeably out of date within a single season. Using the formula above with whatever price you’re actually paying locally gives a far more reliable answer than trusting any fixed figure that inevitably drifts over time.
The Full Math, if You Want It
Our running cost calculator explained guide walks through the complete formula step by step, including a fully worked example and a cost breakdown across several more BTU tiers than covered in this shorter answer.
The Bottom Line
Most portable propane heaters cost somewhere between $0.12 and $0.60 per hour to run at full output, based on an example price of $3.00 per gallon, though your exact figure ultimately depends on your specific heater’s BTU rating combined with whatever propane costs in your area. Use the formula above to arrive at a number that actually reflects your own situation.