Biomass boiler costs don’t end with installation. Mark Brown takes a frank look at the pros and cons of a biomass boiler for a 5 bed detached house.
Work started in the warm August of 2009 when we didn’t need heating. Hot water was supplied by an immersion heater as we didn’t have the Solar Thermal panels up at this point (they came in 2010).
The estimated install was meant to be two weeks but it took six in total. We allocated one half of a double garage to the project in an area co-located with the existing gas-boiler for convenience.
Installation was largely trouble-free. The UK representative of the Manufacturer (KWB) came out for commissioning and observed that one section of pipework was incorrect. It was quickly rectified.
We live in a Conservation area and had planning permission refused for an external flue so we had it route through the corner of the bedroom over the garage. Not a big problem as our installer arranged for builders to come in and box in the flue. We redecorated ourselves.
The KWB Easyfire is a 15kW boiler with a 500l buffer tank. The system provides space and water heating but we also have both gas backup as well as solar thermal and lounge wood stove.
Our system is using wood pellets fed from a hopper. The hopper stores enough for at least seven days in the depth of winter but can last up to two months in a warm summer. It is fully automated, other than filling it up with pellets or emptying the ash (once a year!) no work is required. Our KWB is very reliable.
We installed in 2009 on the assumption that the Renewable Heat Incentive would pay for the investment. We could have had a cheaper boiler make but had to opt for one licenced for use in a smoke-control zone. Total cost of the boiler, buffer tank, flue, labour & VAT came to £15,590 minus £1000 from the (then) Low Carbon Building program grant.
We use bagged wood pellets and need just under 5 tonnes a year. They cost about £230/tonne (delivered + VAT) working out at £1100 pa approx. We take three tonnes per delivery with about two deliveries a year. Note that there are slightly cheaper options but we prefer UK-sourced pellets.
We are lucky enough to have a maintenance contract that covers five years’ work. It works out at about £150 a year this way, but you could pay up to £500 pa if unwilling to pay up front for a contract. This contract includes cleaning the flue and boiler.
Given the information we had in 2009 (and the pending Renewable Heat Incentive) we think we made a good choice. However the RHI has not materialised and, as far as we know, might NEVER pay us a penny for this boiler in its final manifestation.
When deciding upon this form of heating we did compare it to a ground-source heat pump. We didn’t cost up a comparable GSHP but it would only have been suitable if we had been prepared to dig up the floor for underfloor heating plus the garden for the ground loop. A GSHP would need a lot of electricity to run but we wanted to generate most of our own power so it would have put that objective out of reach. Hence biomass was the most local & resilient option.
We have great satisfaction with the boiler and our only regret is the loss of space in the garage. We would recommend domestic biomass for rural areas with large buildings off mains gas.
You can find out more about biomass boilers at green open house events in September. Speak to real homeowners as they share their personal experience of refurbishing their homes as part of SuperHome Open Days. SuperHomes are older homes refurbished by their owners for greater comfort, lower bills and far fewer carbon emissions – at least 60% less! Entry is free. Book now.
Full details of this project are available at Post Carbon Living. You can see this wood pellet boiler in situ at Mark Brown’s SuperHome at Open Days in March and September or by appointment. Mark is a member of Transition Town High Wycombe.
© Mark Brown Aug 2012