Is biomass heating right for your house?
Six things decide whether a house can realistically run on wood pellets: heat demand and insulation, physical space for the appliance, flue and hearth feasibility, dry storage for a season's fuel, delivery access for a bulk lorry, and whether you're prepared to handle fuel and ash. Work through them here before paying for a survey.
Read what's changed recently in pellet prices and grants See what running a pellet system costs and involvesSix checks before you consider a pellet system
Work through these six before you pay for a survey. A yes to all six means biomass is worth costing properly; a no to two or more usually means it isn't.
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Heat demand is high enough to justify the fuel and kit
Older, harder-to-insulate properties with a genuine year-round heat demand suit biomass better than a well-insulated modern build, where the running costs of a pellet system rarely beat a heat pump.
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There is room for the stove or boiler itself
A pellet boiler needs a plant room or utility space for the boiler, hopper and auger (the screw mechanism that feeds pellets from hopper to burner).
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A flue run is physically achievable
The flue liner (the inner sleeve of a chimney or flue system) has to reach the correct height and clear nearby openings and boundaries; an existing chimney does not automatically mean a suitable route.
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You have dry, accessible storage for a season's fuel
A pellet boiler needs roughly 5–8 cubic metres of dry storage for a season's fuel; a garage corner or damp lean-to is not equivalent to a proper store.
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A bulk delivery lorry can reach the storage point
Bulk pellets are blown in from a tanker through a delivery pipe of limited length; a tight terrace access or a long carry from the road can rule bulk delivery out even where storage space exists.
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You're prepared to handle fuel and ash as routine tasks
Topping up the hopper and emptying the ash tray is a regular task.
This checklist is a starting point. Where your answers are mixed, read the house types that suit biomass and the ones that don't before ruling anything in or out.
Houses where biomass rarely works
Some houses are a poor match for pellet heating whatever the enthusiasm behind the idea, and it is worth naming these plainly.
Terraced houses with no external storage
A pellet boiler needs roughly 5 to 8 cubic metres of dry, accessible storage to hold a season's fuel, and that space normally has to sit close to the appliance so the auger (the screw mechanism that feeds pellets from hopper to burner) can reach it without a long, awkward run. A mid-terrace house with no side access, no garage and no room for a hopper in the house itself usually cannot meet this. Bagged pellets stored a few at a time inside the house are an option for a small stove, but they cost more per kilowatt-hour than bulk delivery and involve regular manual handling, which is a fair trade for some households and not for others.
Well-insulated modern builds with low heat demand
Heat demand is the annual energy a building needs for space and water heating, and it is the number that determines whether biomass makes sense at all. A pellet boiler is sized and run most efficiently against a steady, fairly high load; a modern house built to current insulation standards, with a heat demand low enough that a smaller electric system or heat pump could cover it comfortably, gains little from the extra plumbing, flue work and fuel storage a biomass system needs. In that case a heat pump is usually the more straightforward answer, and the comparison in Biomass against a heat pump sets out why.
Properties without bulk delivery access
Bulk pellet delivery arrives by lorry, and the lorry needs a route in that a domestic driveway or a narrow lane does not always provide. Where a property cannot be reached this way, the practical alternative is bagged pellets bought and stored a few at a time, which removes the delivery problem but raises the running cost per kilowatt-hour and adds the ongoing task of carrying bags to the hopper yourself. Pellets: quality, storage and delivery covers what bulk and bagged delivery each actually involve.
None of these conditions is a judgement on the house, only on whether pellet heating is the sensible tool for it. Where one or more of them apply, it is worth working through the running cost arithmetic for the alternative before committing to either, and the running cost calculator is a reasonable place to start that comparison.
Where biomass tends to work well
Biomass tends to suit an older, rural house that is already off the mains gas network, where the alternative is oil, LPG or electric storage heaters. These properties are usually larger and less well insulated than a modern build, which pushes annual heat demand (the total energy needed for space and water heating over a year) up towards the level where a pellet boiler's running costs start to compare favourably with oil. A small, well-insulated flat with low heat demand is a different case, and is covered separately below.
High heat demand changes the arithmetic
A pellet boiler has a real fuel cost per kilowatt-hour, and that cost only looks competitive against oil or LPG once the house is using enough kilowatt-hours a year to make the comparison meaningful. Solid-wall Victorian and Edwardian houses, farmhouses and converted barns commonly fall into this bracket, because their heat loss is higher than a house built to current Building Regulations. The running cost calculator lets you put your own heat demand figure in.
Room for the appliance and a flue that can take it
A pellet stove or boiler needs a hearth or plant room with clearances to combustible materials, and a flue liner (the inner sleeve run through or up the chimney) rated for the appliance's flue gas temperature. Older rural properties more often have an existing chimney breast or the outbuilding space to accommodate a boiler and its flue run than a mid-terrace house does. Whether your specific chimney or wall can take a flue is a question for a competent installer, not something this page can answer for your house.
Dry storage and a lorry that can reach it
Bulk pellets are delivered by tanker and blown into a store, so the property needs dry, accessible storage space for a season's fuel and a route a delivery vehicle can actually use, whether that's a long drive, a farm track or a hardstanding yard. A detached rural property with an outbuilding or purpose-built store and vehicle access from a road is the straightforward case. A terraced house with no off-street storage and no way for a tanker to reach a hopper is the case where biomass usually stops making sense, regardless of how well the rest of the house suits it.
If your property fits this pattern, treat it as a starting point rather than a conclusion: run the numbers on the calculator, and if you're still weighing biomass against the main low-carbon alternative, see the comparison with heat pumps for the conditions under which each one wins out.
What to do with this assessment
If your house passes on heat demand, storage and delivery access, the running cost calculator is the next thing to look at. If it does not, a heat pump comparison or a look at your oil options may be more useful than a survey.