What Size Patio Heater Do I Need? A BTU and Coverage Guide

The most common patio heating mistake is buying on price and guessing on size. Too small and the space never feels warm; too big and you overpay to run it. Here's how to size a patio heater properly for a Canadian backyard or terrace.

Want us to do the math for you? Take the free 2-minute quiz or send us your dimensions.

The quick rule of thumb

Sizing comes down to output versus area and conditions. As a rough guide, a high-output gas heater like the Tungsten 500 Gas (up to 43,000 BTU) comfortably covers a large open seating area, while a mid-size electric heater (2,300W to 4,500W) suits a smaller covered spot. But three things change the answer: ceiling height, how exposed the space is, and where you can mount the heater.

The three things that really decide size

Ceiling and mount height. Radiant heat spreads as it travels down. Mounted higher, one heater covers a wider area but feels gentler directly below; mounted lower, it feels stronger over a smaller footprint. Most Bromic heaters have a recommended mounting-height range, get that right before you worry about BTU. For the actual minimum heights and clearances, see our Bromic heater installation and placement guide.

How exposed the space is. A fully open patio in the wind needs more output, and favours gas, over the same-size covered patio. Covered and semi-enclosed spaces hold heat, so a smaller electric heater does the job. This is also the gas-versus-electric decision, covered in Gas or Electric Patio Heaters?

Where you can mount. Wall, ceiling, or portable changes which models fit and how the heat lands. Sometimes two smaller heaters placed well beat one big one placed poorly.

One heater or several?

For an even, comfortable space, coverage beats raw power. A long terrace is better served by a few heaters spaced along it, each on a zone, than one oversized unit at one end. That's also where Affinity controllers come in, run only the zones you need. If you're not sure which family to size around, start with the Bromic buyer's guide.

Don't forget running cost

A bigger heater costs more to run at full. Sizing correctly, and dimming or zoning, keeps the bill down. See real figures in What It Costs to Run a Patio Heater in Canada.

Frequently asked questions

What size patio heater do I need?

It depends on your area, ceiling or mount height, and how exposed the space is, not square footage alone. As a guide, a 40,000 to 43,000 BTU gas heater covers a large open area, while a 2,300W to 4,500W electric heater suits a smaller covered space. Send us your dimensions for an exact spec.

How many BTU do I need to heat a patio?

For open spaces, plan on a high-output gas heater in the 40,000 BTU range per seating zone; covered spaces need less. Ceiling height and wind exposure move the number, so treat BTU as a starting point, not the whole answer.

Is one big heater or several small ones better?

For even comfort, several well-placed heaters usually beat one oversized unit, especially on a long or open space. It also lets you zone the area and run only what you need.

How high should a patio heater be mounted?

Follow the model's recommended mounting-height range. Higher spreads heat over a wider, gentler area; lower concentrates it. Getting the height right matters as much as the output rating. Full mounting heights, clearances and recessed options are in the installation and placement guide.

Get an exact spec for your space

Send us your patio dimensions, ceiling height, and a couple of photos. We'll return the right heater size, count, and placement, at no charge.

Take the 2-minute quiz · Request a free heating layout · call 1 (888) 851-8852

Browse the full range: Bromic Heating at PremiumBackyard.ca