Patio Heat and Fire Pits
Patio Heater BTU Calculator: How Many BTU or Watts for Your Patio
Quick answer
A standard 46,000 BTU propane patio heater warms about a 9 foot radius, roughly 250 square feet, on a calm evening in the 50s. Plan about 185 BTU or 30 watts of infrared per square foot, add about 40 percent below 50 F or in a breeze, and use one full-size heater per 250 square feet of seating.
Patio heaters do not heat air the way a furnace does. Mushroom and pyramid propane heaters and infrared electric heaters are radiant: they warm people and surfaces within their reach, which is why makers rate them by heat radius or coverage area rather than by room volume. This calculator uses those published coverage figures, then adjusts for how cold it is and how exposed the patio is. Enter your seating area and conditions to get the BTU or watts, how many heaters, and the propane or electricity cost per hour. For fuel planning, see the propane tank runtime calculator.
Patio heater BTU calculator
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Patio heaters that fit this space
Top matches update when you calculate.
Hiland HLDS032-B Tabletop Propane Patio Heater
$119.99A 38 inch, 11,000 BTU CSA-approved tabletop heater with thermocouple and anti-tilt shutoffs that runs on a 1 lb cylinder or a 20 lb tank with a hose.
Best for: warming a bistro table
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Cuisinart Portable Tabletop Patio Heater, 11,000 BTU
$149.99An 11,000 BTU tabletop heater rated to warm about 30 sq ft, with an anti-tilt shutoff, burner screen guard and adjustable dial.
Best for: small balconies and tailgates
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Fire Sense 61130 Standing Propane Patio Heater, 48,000 BTU
$131.24A 48,000 BTU mushroom heater rated for an 18 ft heat diameter, with piezo ignition, a tilt shutoff valve and roughly 10 hours per 20 lb tank.
Best for: warming a dining set outdoors
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Amazon Basics 46,000 BTU Propane Patio Heater with Wheels
$162.74A 46,000 BTU freestanding heater rated for an 18 ft diameter with one-touch ignition, a tilt shutoff and a water box to weigh down the base.
Best for: a low-cost standing heater
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Mr. Heater Big Buddy PRO 18,000 BTU Portable Heater
$146.48A portable radiant and convection heater with 4,000, 9,000 and 18,000 BTU settings rated to heat up to 450 sq ft, with a built-in fan.
Best for: garages, porches and enclosed patios
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Fire Sense 02117 Offset Pole Electric Infrared Patio Heater
$210.00A 1500 W telescoping offset infrared heater that runs on a household circuit, adjusts from 72 to 93 inches tall and has tip-over protection.
Best for: plug-in heat with no propane
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Hiland HLDS01-SSHST 48,000 BTU Patio Heater with Wheels and Table
$238.99A 48,000 BTU stainless mushroom heater with wheels and a built-in table, from a brand that sells complete replacement burners and parts on Amazon.
Best for: large patios that want a drink ledge
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Dr. Infrared Heater DR-239 3000W Wall or Ceiling Patio Heater
$293.20A 3000 W, 240 V carbon infrared heater with an IP55 rating, wall and ceiling brackets, remote control and ETL listing.
Best for: covered patios with a 240V circuit
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Hiland HLDS01-CGTHG Quartz Glass Tube Pyramid Patio Heater
$424.99A 94 inch commercial-grade pyramid heater with a one-piece quartz glass flame tube, 40,000 BTU, thermocouple and anti-tilt devices and CSA approval.
Best for: visible flame ambiance with real heat
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Bromic Tungsten Smart-Heat 4000W Electric Patio Heater
$693.70A dual-element 4000 W stainless infrared heater rated for 130 sq ft, wall or ceiling mounted, with IPX4 protection and smart-control dimming compatibility.
Best for: high-end covered outdoor rooms
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Flame King YSN230 20 lb Propane Tank with Gauge
$69.99A DOT-certified, powder-coated 20 lb steel cylinder with an OPD valve and a built-in level gauge, shipped empty and purged.
Best for: a spare tank so dinner never stalls
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Flame King Digital Propane Tank Scale
$15.38A handheld hook scale that reads remaining propane by weight on 5 to 40 lb tanks, with auto power-off.
Best for: knowing if the tank will last the cook
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How many BTU do I need for my patio?
| Seating area | Propane BTU | 46,000 BTU heaters | Electric infrared watts | 4,000 W heaters |
|---|---|---|---|---|
| 100 sq ft | 19,000 BTU | 1 | 3,000 W | 1 |
| 150 sq ft | 28,000 BTU | 1 | 4,500 W | 2 |
| 200 sq ft | 37,000 BTU | 1 | 6,000 W | 2 |
| 300 sq ft | 56,000 BTU | 2 | 9,000 W | 3 |
| 400 sq ft | 74,000 BTU | 2 | 12,000 W | 3 |
| 600 sq ft | 111,000 BTU | 3 | 18,000 W | 5 |
What coverage do popular patio heaters claim?
| Heater | Output | Published coverage | Mount |
|---|---|---|---|
| Hiland HLDS032-B Tabletop Propane Patio Heater | 11,000 BTU | Not listed | tabletop |
| Cuisinart Portable Tabletop Patio Heater, 11,000 BTU | 11,000 BTU | 30 sq ft | tabletop |
| Fire Sense 61130 Standing Propane Patio Heater, 48,000 BTU | 48,000 BTU | 9 ft radius (about 254 sq ft) | freestanding |
| Amazon Basics 46,000 BTU Propane Patio Heater with Wheels | 46,000 BTU | 9 ft radius (about 254 sq ft) | freestanding |
| Mr. Heater Big Buddy PRO 18,000 BTU Portable Heater | 18,000 BTU | 450 sq ft | freestanding |
| Fire Sense 02117 Offset Pole Electric Infrared Patio Heater | 1,500 W | Not listed | freestanding |
| Hiland HLDS01-SSHST 48,000 BTU Patio Heater with Wheels and Table | 48,000 BTU | Not listed | freestanding |
| Dr. Infrared Heater DR-239 3000W Wall or Ceiling Patio Heater | 3,000 W | Not listed | wall |
| Hiland HLDS01-CGTHG Quartz Glass Tube Pyramid Patio Heater | 40,000 BTU | Not listed | freestanding |
| Bromic Tungsten Smart-Heat 4000W Electric Patio Heater | 4,000 W | 130 sq ft | wall |
How does temperature change how much heat I need?
| Outdoor temperature | Heat needed | What it means |
|---|---|---|
| 60 F or warmer | Light warmth, about 0.6 x | Tabletop or a single heater set low |
| 50 to 59 F | Planning baseline, 1 x | One full-size heater per 250 sq ft |
| 40 to 49 F | About 1.4 x | More heaters closer to seating |
| Below 40 F | About 1.8 x, and still limited | Radiant heat warms people near it, not the air; add wind screens and blankets |
How is patio heater size calculated?
- Propane BTU = seating area x 185 x temperature factor x wind factor
- Electric watts = seating area x 30 x temperature factor x wind factor
- Heaters = total / output per heater, rounded up, placed so their heat circles overlap the seating
- Propane per hour = BTU per hour / 21,548 BTU per pound; electric cost = kW x your rate
The temperature factor runs from about 0.6 in the 60s F to 1.8 below 40 F, and the wind factor from 1.0 for a covered, sheltered patio to 1.6 for an open, breezy one. Radiant heat reaches a person regardless of air temperature, but wind strips warmth off skin and bends propane flames, so a wind screen often adds more comfort than a second heater. Infrared electric heaters mounted under a covered patio or pergola, such as the Bromic Tungsten Smart-Heat 4000W Electric Patio Heater or the Dr. Infrared Heater DR-239 3000W Wall or Ceiling Patio Heater, deliver the most comfort per watt because the heat is aimed straight at the seating.
Should I buy a propane or electric patio heater?
Propane freestanding heaters, such as the Amazon Basics 46,000 BTU Propane Patio Heater with Wheels and the Fire Sense 61130 Standing Propane Patio Heater, 48,000 BTU, go anywhere on an open patio with no wiring, but a 20 lb tank lasts only about 9 hours on high and swapping tanks is part of ownership. Pyramid flame heaters like the Hiland HLDS01-CGTHG Quartz Glass Tube Pyramid Patio Heater add ambiance with slightly less output. Electric infrared heaters cost less per hour in many areas, never run out of fuel and can mount out of the way, but they need a suitable outlet or a dedicated 240V circuit installed by a licensed electrician. Compare in electric vs propane patio heaters.
Frequently asked questions
How much area does a 40,000 BTU patio heater cover?
Freestanding propane heaters of about 40,000 to 48,000 BTU are commonly rated for a heat radius of around 8 to 10 feet, which is roughly 200 to 300 square feet of seating on a calm evening. Coverage shrinks in wind and at lower temperatures. For larger patios, several heaters spaced so their heat circles overlap work better than one heater in the middle.
How many patio heaters do I need for 400 square feet?
At about 185 BTU per square foot, 400 square feet of seating needs roughly 74,000 BTU on a calm evening in the 50s F, which is two 46,000 BTU freestanding heaters. Below 50 F or in a breeze, plan on three. With electric infrared, about 12,000 watts, or three 4,000 watt units aimed at the seating, is a similar planning figure.
How much does it cost to run a patio heater?
A 46,000 BTU propane heater burns about 2.1 pounds of propane an hour on high, so a 20 lb tank lasts about 9 hours; divide your refill price by 9 to get the hourly cost. A 4,000 watt electric infrared heater uses 4 kWh an hour, about 68 cents at a 17 cent rate. Running heaters on a lower setting cuts either cost.
Do patio heaters work in cold weather?
They help, but with limits. Radiant patio heaters warm people and surfaces in their reach rather than the air, so in the 40s F they make seating comfortable close in, and below about 40 F they take the edge off rather than making it warm. Wind is the bigger enemy: a sheltered corner, wind screens and blankets make a larger difference than adding heater output.
Can I use a propane patio heater under a covered patio?
Only if the heater manufacturer permits it and you keep the listed clearance to the ceiling, which is often several feet above the heater top. Many freestanding propane heaters are designed for open-air use and warn against overhead covers and enclosed spaces. For covered patios and pergolas, electric infrared heaters mounted per their instructions are usually the safer, more efficient choice.
Researched, not professional advice. This page is compiled from published specifications, manuals, labels and owner-review consensus, not hands-on testing. Follow the manufacturer's instructions and product label, and consult a qualified professional where safety, chemicals, fuel or structures are involved. As an Amazon Associate we earn from qualifying purchases.