What the calculator works out for you
A pellet heating running cost calculator takes the heat your house needs over a year and turns it into a fuel spend, using the price of pellets and the efficiency of the appliance burning them. It does not know what you will actually pay, because pellet prices move and appliances perform differently depending on how well they are serviced and installed. What it gives you is a worked figure built from your own numbers, which is a far better starting point than a flat estimate pulled from somewhere else.
The result from the pellet heating running cost calculator is a range, not a quotation and not a savings promise. It sits alongside the sum behind it so you can see exactly where the number came from and change any part of it yourself.
The arithmetic behind the number
The underlying sum is short: heat demand in kilowatt-hours (kWh), divided by the appliance's efficiency, multiplied by the price of pellets per kWh. Heat demand is the energy your house needs over a year for space and water heating, and it is the figure that drives everything else. Get it wrong and every other number in the calculation is wrong too, which is why it is worth getting from a proper estimate.
At 4.5p per kWh for ENplus-A1 pellets, a wood pellet quality standard that sets limits on moisture, ash content and consistency, a well-insulated four-bedroom house with an annual heat demand of 20,000 kWh would spend around £900 a year on fuel. That figure assumes 90% appliance efficiency, and it comes from Ofgem data for the first quarter of 2024, so it will have moved since. It also excludes servicing, electricity for the auger and ignition, and any delivery charge, all of which sit on top of the fuel cost itself.
If your heat demand is different, the whole figure scales with it. A house needing 12,000 kWh a year will spend roughly 60% of that £900 on the same pellet price and efficiency, and a draughtier house needing 28,000 kWh will spend proportionately more. If you do not already have a heat demand figure for your house, the home heat demand estimator works it out from floor area, insulation and a few other details, and the guide to that tool explains what each input means.
Mistakes that throw the number off
- Using the bag price instead of the delivered bulk price. Pellets bought by the bag from a local stockist usually cost more per kWh than pellets delivered by tonne, so pricing against bag rates overstates the gap to oil or LPG.
- Assuming a fixed efficiency. A new, well-serviced boiler can run close to 90% efficient. An appliance that has gone two years without a sweep, or one fed by a poorly sized flue, runs lower, and the fuel cost rises to match.
- Leaving out electricity. The auger, the screw mechanism that feeds pellets from the hopper to the burner, and the ignition element both draw mains electricity. It is a smaller cost than the pellets themselves, but it is not zero.
- Comparing against last year's oil price. Fuel prices for oil, LPG and pellets move independently of each other, so a comparison done a year ago can be out of date in either direction.
- Treating a grant as a running cost saving. A capital grant towards installation, such as the Boiler Upgrade Scheme (BUS), affects what you pay upfront. It does not change the cost per kWh of the fuel you burn afterwards.
What the figure cannot account for
A running cost figure is an arithmetic illustration. It cannot see how your household's heating habits will change, what pellet prices will do next winter, or how well the appliance will actually be maintained over its life. Those are the things that move the real bill away from the modelled one, in either direction.
Servicing is the clearest example. A biomass boiler needs an annual service and periodic sweeping to keep the flue liner, the inner sleeve of the chimney or flue system, clear and the appliance running at its rated efficiency. Running costs and maintenance sets out what that servicing typically involves and how it affects the sums here. None of it appears in a fuel-only running cost figure, so it is worth adding on separately.
Using the figure to weigh biomass against the alternatives
A running cost figure only means something next to an alternative. The useful comparison is pence per kWh delivered. Biomass against a heat pump works through that comparison directly, including the house types where a heat pump tends to come out ahead on running cost and the ones where biomass holds up better.
Pellet prices themselves are worth checking against something current. UK wood pellet prices: where they stand in summer 2025 covers the more recent movement in bulk and bag pricing.
Where to go next
Run the pellet heating running cost calculator with your own heat demand and a current pellet price to get a figure specific to your house. If you do not yet have a heat demand figure, work one out first with the home heat demand estimator, since the running cost figure is only as good as that input. From there, read running costs and maintenance for the servicing costs that sit outside the fuel arithmetic, and biomass against a heat pump if you are still deciding between systems.