Patio Heater Propane Cost Calculator

A patio heater burns propane to throw radiant heat.
The cost per hour comes down to two numbers: BTU per hour and price per pound of propane.

The math:

lb_per_hour = BTU_per_hour / 21,600 cost_per_hour = lb_per_hour × price_per_lb

Propane delivers 21,600 BTU per pound.
That number is constant — it does not vary by brand or season, only by source rules.
Price per pound varies wildly: a 20 lb exchange tank at Blue Rhino runs about $25-30 (just over $1.30 per pound), while filling your own tank at U-Haul or Tractor Supply costs $15-20 (less than $1 per pound).
Bulk propane delivered to a large stationary tank runs $2-3 per gallon, or about 50-70 cents per pound.

A worked example.
A standard mushroom-style patio heater is rated 40,000 BTU/h.
That is 40,000 / 21,600 = 1.85 lb of propane per hour at full output.
At $1.30 per pound (exchange tank), that is $2.40 per hour.
A 20 lb tank lasts about 11 hours at full output.
Three evenings of patio dinners and you are buying another tank.

Wall-mounted infrared heaters use less.
A 30,000 BTU/h infrared heater costs about $1.80 per hour at $1.30 per pound and delivers most of its heat as direct radiation rather than warming the air around the heater.
That is why restaurants increasingly use infrared over mushroom heaters: same warmth on guests at half the propane.

Output settings dramatically change consumption.
A 40,000 BTU/h heater on the lowest setting often runs at 15,000-20,000 BTU/h, cutting hourly cost in half.
Most people have their patio heater on too high without thinking — the gauge does not show consumption, just output, and full-on is rarely needed once the seating area is warm.

A few practical points.
Patio heaters are about 30-40% efficient at warming people in an outdoor space (the rest of the heat rises and dissipates).
Indoors they are 100% efficient but also a carbon monoxide hazard, so never use a patio heater inside a garage or covered porch with limited ventilation.
Wind dramatically reduces effectiveness — a 5 mph breeze can cut perceived warmth in half.
For small patios, a 20,000 BTU/h tabletop heater costs less than $1 per hour and is plenty for a 4-person table.

The economics versus a built-in propane fire pit.
A 60,000 BTU fire pit costs about $2.78 per hour at typical propane prices.
But fire pits radiate to a single circle around them, while patio heaters cast warmth on a wider area.
For groups, two patio heaters often beat one fire pit in actual warmth delivered.