Where Does the Heat Go? Comparing Pellet, Mushroom and Directional Radiant Patio Heaters

The short version

• BTU does not tell you where the heat goes.
• Pellet, mushroom-style and directional radiant heaters use different geometries.
• Published coverage claims use different units and definitions, so they should not automatically be compared.
• Pellet heaters give you a visible flame and a gathering point.
• Directional radiant heaters are designed around a defined occupied area.
• Choose based on the outcome you want, not simply the largest number.

Every outdoor heater sold in Canada leads with a number. Usually BTU, sometimes a coverage area in square feet, occasionally a distance in feet. Those numbers do a lot of work in the buying decision and very little work explaining what will actually happen on your deck in October.

We sell one of the three categories below, so read the rest with that in mind. What follows is what several manufacturers publish, what those figures do and don't tell you, and how the three main types of outdoor heater are built to behave.

Why the biggest BTU number doesn't necessarily win

Here is what four manufacturers published as of August 2026.

Timber Stoves lists its Big Timber pellet heater at 90,000 BTU with a 12-foot maximum heating radius. Bromic lists the Tungsten Portable at 38,500 BTU covering up to 215 square feet. Even Embers is sold at 70,000 BTU and 100 square feet. Forestwest publishes a heat area of about 134 square feet for its Firestorm, and no BTU figure at all.

Line those up and they look like a comparison. They aren't one.

Three of them are areas. One is a radius. A 12-foot radius, if you simply draw it as a circle, works out to roughly 450 square feet. But that's exactly the kind of calculation we don't think a buyer should make from these specifications. We don't know that Timber's "maximum heating radius" and Bromic's "coverage area" were defined, measured or tested the same way.

It gets stranger further down the shelf. One retailer lists a pellet heater at 75,000 BTU with a "heat radius of 120 square feet," which is not a unit that exists. One manufacturer's page for a single propane heater gives three different figures in three different places: 15 feet, a 10-foot radius, and an 18-foot heat radius.

BTU is the part most people misread. On an electric heater it is often just the wattage converted. Our own Bromic Tungsten Electric is listed at up to 6,000W, which works out to about 20,000 BTU per hour. Same quantity, different units. On combustion appliances, a BTU/hr rating may describe thermal input rather than the amount of useful radiant heat reaching a person at a particular distance.

If you want the arithmetic behind sizing a heater to a space, we cover it separately in What Size Patio Heater Do I Need?

Three heaters, three different jobs

Set the numbers aside and the choice gets easier, because these three are built around genuinely different ideas.

"I want a fire people gather around."

Pellet. Heat and light originate at a visible fire in the middle of the space. Where people put themselves relative to that fire is the whole layout. You get flame, sound and something to stand near with a drink in your hand, which no radiant panel will ever give you.
The trade is that you are moving people to the heat rather than the other way round, and you are loading pellets and clearing ash as part of owning it.

"I want simple, familiar heat around a central heater."

Mushroom. A reflector mounted above head height redirects heat outward and downward from a central burner. Everyone recognises the shape, they are inexpensive, and you can buy one anywhere.
How well it works for you depends on the reflector geometry and where people sit relative to the column. An exposed, breezy site is the harder case for this arrangement.

"I already know where people will sit. I want to heat that zone."

Directional radiant. Mounted or positioned so the energy is aimed at a defined area: the dining table, one end of the terrace, the walk between the house and the hot tub. Placement and aim are design decisions you make once.
The trade is that there is no flame and nothing to look at. Fixed models need mounting, and gas or hardwired electric needs a licensed trade.

If a directional heater is the direction you're heading, the portable patio heaters are the ones you can position yourself without a trade, and the outdoor heater guide walks through fixed versus portable and gas versus electric.

What does "coverage" actually mean?

Harder to answer than you would expect. We went looking for the testing behind these coverage numbers and came up empty for every product in this article, including the one we sell.

A coverage figure only means something if you know what counted as heated. A one-degree rise? Five? At what outdoor temperature, in still air or in wind, at what mounting height? Measured with instruments on a real patio, or modelled on a computer?

There is an industry standard test method for patio heater performance, ASTM F2644, which measures temperature distribution and effective heated area for gas and electric radiant heaters. We could not find it cited on any of the product pages above.

Bromic publishes more of the surrounding detail than anyone else here, including a reach, a spread and an 8 mph wind rating. What the published material does not establish is whether the 215 square feet was determined at that wind speed, in still air, or at a particular outdoor temperature.

Which is why we don't suggest choosing an outdoor heater by multiplying or dividing published coverage numbers.

Questions worth asking

• What does "coverage" mean on this spec sheet?
• At what outdoor temperature?
• At what wind speed?
• At what distance from the heater?
• Was it measured, modelled or estimated?

So which one should you buy?

None of this makes one kind of heater better than another. A Bromic cannot give you a fire to stand around on an October evening. A Timber can. A pellet heater cannot be bracketed to a wall, aimed at a dining table and left alone all winter. A Bromic can.

Work out what you want the evening to look like before you compare a single spec sheet. Where will people actually sit? Is the space covered? Does the wind come across it? Do you want something to gather around, or something you stop noticing because you are simply warm?

Don't ask which outdoor heater is best. Ask what you want the heater to do.

Comparing specific brands rather than heater types? That's a different question, and we keep it separate in the patio heater comparison guide.

Still working it out?

Not sure which type fits your space? Tell us the size of the area, whether it's covered or exposed, where people actually sit, and what gas or electrical supply you already have. We'll help you work through which heating approach makes sense — even if the answer isn't one we sell.

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