Patio Heater Calculator
Calculate the number and BTU of patio heaters needed for your outdoor space. Enter values for instant results with step-by-step formulas.
Reviewed by Abdullah, Technical Content Specialist
Formula
BTU Needed = Area (sq ft) x Temp Rise x Wind Factor x Roof Factor | Heaters = max(BTU/Heater BTU, Area/Coverage)
Total BTU requirement is calculated by multiplying the area by the desired temperature increase and a wind exposure factor. The number of heaters is the larger of the BTU-based count or the coverage-area-based count to ensure both sufficient heat output and spatial coverage.
Worked Examples
Example 1: Medium Patio with Propane Heaters
Problem:Calculate heaters needed for a 20 x 15 foot open patio, wanting a 20-degree temperature rise with moderate wind, using 46,000-BTU propane heaters.
Solution:Area: 20 x 15 = 300 sq ft\nBTU needed: 300 x 20 x 3.0 (moderate wind) = 18,000 BTU\nHeaters by BTU: 18,000 / 46,000 = 1 (rounded up)\nHeaters by coverage: 300 / 314 = 1 (rounded up)\nHeaters needed: 1 (BTU and coverage both suggest 1)\nNote: For better coverage, 2 heaters recommended
Result:1-2 heaters at 46,000 BTU each | ~$1.60/hr operating cost
Example 2: Large Restaurant Patio
Problem:Calculate for a 40 x 25 foot exposed patio, 25-degree rise, using 46,000-BTU propane heaters at $250 each.
Solution:Area: 40 x 25 = 1,000 sq ft\nBTU needed: 1,000 x 25 x 4.0 (exposed) = 100,000 BTU\nHeaters by BTU: 100,000 / 46,000 = 3 (rounded up)\nHeaters by coverage: 1,000 / 314 = 4 (rounded up)\nHeaters needed: 4\nEquipment: 4 x $250 = $1,000
Result:4 heaters needed | $1,000 equipment | ~$6.40/hr operating cost
Frequently Asked Questions
How many BTUs do I need for my patio?
The BTU requirement for outdoor heating depends on the area size, desired temperature increase, and wind exposure. A general rule is to provide 10 to 20 BTUs per square foot for sheltered areas and 30 to 40 BTUs per square foot for open, windy locations. For a typical 200-square-foot covered patio, you need approximately 4,000 to 8,000 BTUs. For an open 300-square-foot space wanting a 20-degree temperature rise, you may need 18,000 to 24,000 BTUs. Standard standing propane patio heaters produce 40,000 to 48,000 BTUs each, which is enough to heat a 20-foot diameter circle in moderate wind conditions. Always overestimate rather than underestimate because you can turn heaters down but cannot make an undersized heater produce more heat.
What type of patio heater is most efficient?
Infrared electric heaters are the most energy-efficient option because they heat objects and people directly rather than heating the air, which means wind does not immediately disperse the warmth. They convert about 90 percent of their energy input into radiant heat. Natural gas patio heaters are the most cost-efficient for frequent use because piped natural gas costs significantly less per BTU than propane or electricity. Propane standing heaters are the most versatile since they require no utility connections and can be moved freely. Electric heaters are best for covered patios and small spaces where running natural gas lines is impractical. For large open areas, multiple infrared heaters positioned strategically provide better coverage than fewer large propane heaters.
How much does it cost to run a patio heater?
Operating costs vary significantly by fuel type. A standard 46,000-BTU propane patio heater consumes approximately 2 pounds of propane per hour, which costs about 1.50 to 2.00 dollars per hour based on current propane prices. A 20-pound propane tank costs 15 to 20 dollars to refill and lasts approximately 8 to 10 hours at full output. Natural gas heaters cost about 0.50 to 1.00 dollars per hour because piped gas is cheaper per BTU than bottled propane. Electric heaters running at 1,500 watts cost approximately 0.18 to 0.30 dollars per hour depending on your electricity rate. Over a six-month season using the heater four hours per week, annual costs range from 50 to 200 dollars for electric to 200 to 500 dollars for propane.
How far apart should patio heaters be placed?
Patio heaters should be spaced based on their effective heating radius, which varies by type and BTU output. Standard 46,000-BTU standing propane heaters heat an area approximately 15 to 20 feet in diameter, so place them 15 to 18 feet apart for overlapping coverage. Tabletop heaters with 10,000 to 12,000 BTUs have a heating radius of only 4 to 6 feet. Wall-mounted infrared heaters cover 10 to 16 feet wide depending on mounting height and wattage. Position heaters so that their coverage circles overlap by about 20 percent to eliminate cold spots between units. Place heaters near the seating areas rather than at the edges of the space, and consider that wind will push heat in one direction.
References
Reviewed by Abdullah, Technical Content Specialist · Editorial policy