Heating
What kW pellet or wood stove do you need?
Design heat load in kW from the area the stove actually heats, then the shop band for a pellet stove and for a wood stove.
Quick answer
Stove size is the heat the room loses on a cold day, not the biggest number on a showroom tag. At a standard 2.7 m ceiling in a temperate climate the design load is about 95 W/m² for a poorly insulated house, 64 W/m² for an average one and 33 W/m² for a well insulated one — the same seasonal figures as the gas calculator (170, 115 and 60 kWh/m²) divided by 1,800 equivalent full-load hours. Worked example: 80 m², average insulation, 2.7 m ceilings → 80 × 64 W = 5.1 kW. The pellet stove to buy is the next shop band up, 6 kW. A pellet stove only turns down to about 30% of its nameplate, so a 12 kW unit cannot idle low enough for that room.
Heat load
5.1 kW
- Pellet stove to buy
- 6 kW (turns down to ~1.8 kW)
- Wood stove to look for
- about 7 kW
Already own the stove? Pellet consumption calculator
Design load at 2.7 m in a temperate climate: 95 W/m² poor, 64 W/m² average, 33 W/m² good — the gas calculator’s 170, 115 and 60 kWh/m² divided by 1,800 full-load hours. Ceiling and climate scale that figure. A pellet stove only modulates to about 30% of its nameplate, so the band is the smallest shop size that still covers the load. This is not a flue or installation calculation.
How it works
The expensive mistake is buying a size up “to be safe”. A 12 kW pellet stove bottoms out around 3.6 kW. If the room needs 5 kW on a hard frost and closer to 2 kW on a mild evening, the big stove lights, overshoots, dies and lights again. The glass blacks, the auger works in bursts, and the room temperature swings. Shop bands are 6, 8, 10, 12 and 14 kW: take the smallest one that still covers the cold-day load. Below about 2 kW even a 6 kW stove is too much — that room wants a radiator, not a fire.
Enter the floor area you actually leave open to the stove, not the cadastral size of the house. An open kitchen and living room share the heat; a corridor and closed bedrooms do not. One air stove that comes out over 14 kW is telling you to heat a zone, or to keep the boiler. Ceiling height scales the load against 2.7 m (a 3.2 m room is about 19% more), and a cold mountain climate multiplies by about 1.35, a mild coast by 0.8. Once the kW is settled, the pellet consumption calculator turns that stove into bags per week. A magnetic stove thermometer shows whether the fire is in its useful band, and a heat-powered stove fan pushes warmth into the next open room — it does not fix a stove that was bought too big.
| Insulation | W/m² at 2.7 m, temperate | Same house on the gas page |
|---|---|---|
| Poor — pre-1990, single glazing | 95 W/m² | ~170 kWh/m² per season |
| Average — some upgrades | 64 W/m² | ~115 kWh/m² per season |
| Good — insulated, modern windows | 33 W/m² | ~60 kWh/m² per season |
Highlighted links go to Amazon.
Frequently asked questions
Why not buy the next pellet stove size up?+
Because the minimum power is about 30% of the nameplate, and you feel that floor every mild day. A 6 kW stove can settle near 1.8 kW; a 12 kW stove is still pushing about 3.6 kW when it is “on low”. If the room needs less than that, the stove short-cycles: sooty glass, a noisy auger and a room that is alternately too hot and cooling off. Cover the cold-day load with the smallest band that does it. Headroom belongs on a boiler, not on a pellet stove in a living room.
Will one stove heat the whole house?+
It heats the room it stands in, and the rooms you leave open to it. Closed doors down a corridor stay cold, and a staircase dumps heat upstairs while the living room is still climbing. If the calculator goes past 14 kW for a pellet stove (or 12 kW for a wood stove), you are asking one air stove to do a boiler’s job. Size the open living area, and let the existing heating cover the bedrooms.
Is 1 kW per 10 m² the right rule?+
1 kW per 10 m² is 100 W/m². That is roughly an uninsulated house, close to the 95 W/m² this calculator uses for poor insulation — not the figure for an average house (64 W/m²) and not for one with insulation and modern windows (33 W/m²). Used on a renovated flat it buys a stove a full band too big. It also ignores ceiling height: the rule assumes about 2.7 m.
Why is the wood stove a different kW from the pellet stove?+
The heat the room needs is the same number. What changes is how the stove delivers it. A pellet stove modulates, so the nameplate can sit just above the load and the fire turns itself down. A wood stove does not: a normal burn should not be the bellows-wide-open burn, so the nameplate wants about 20% of headroom, inside the 5–12 kW sizes you can actually buy. A 5.1 kW room is a 6 kW pellet stove and about a 7 kW wood stove.
As an Amazon Associate I earn from qualifying purchases — the price does not change for you.