Jeff Howell solves readers' property nightmares. This week: wood-pellet vs gas boilers
Wood pellets or gas?
Q: What is your opinion on wood-pellet boilers? I have an old-type central heating system using an Ideal Mexico gas boiler which has served me well, and I’m still able to get parts for it. However, I’m told that a wood-pellet boiler would be a cheaper and more reliable system to run.
A: Wood-pellet boilers are receiving a lot of publicity, due to the idea that burning wood is “carbon neutral” and will therefore help the UK government meet its EU renewable-energy targets by 2020. Most of this will be through pellets being burned in power stations to generate electricity – for which, you will not be surprised to hear, the generating companies receive a handsome public subsidy – but domestic wood-pellet boilers can also qualify for a government grant, under the “Renewable Heat Incentive”. However, taxpayer subsidy does not mean that heating your home with wood will be cheaper than using gas, or that such a system will somehow be more reliable.
Readers might be puzzled by the idea that burning wood can be carbon-neutral since, by its nature, wood combustion emits smoke and carbon dioxide. But the plan is that for every tree cut down for burning, a new one will be planted, and as that tree grows it will absorb carbon dioxide from the atmosphere. So in 100 years’ time we should be back to square one, carbon-wise. Slightly late for that 2020 target date, but let’s give them the benefit of the doubt for now.
What troubles me most about domestic wood-pellet boilers is that when you install one of these things, you are effectively making yourself reliant on a small number of firms to supply you with the fuel. The pellets are made by mincing-up trees or waste timber, and forcing the resulting mash at high pressure through holes in a die. This is an industrial process that itself uses fuel. The rapid recent growth in wood-pellet usage means that Europe is no longer able to supply enough timber, so increasing quantities of pellets are now being manufactured in Canada and shipped across the Atlantic. So the industry might not be as “carbon neutral” as first appears. Prices of wood pellets are rising, and the growing demand for wood for pellets is also raising the price of timber used in construction and other processes. According to a recent report in The Economist magazine, this is affecting European pulp and paper companies, and threatening the survival of the British furniture industry. As so often with the UK government’s commitment to be “green”, the law of unintended consequences seems to be applying itself.
Regarding your own decision on whether to buy a wood-pellet boiler, you will also have to consider whether you have enough storage space for the fuel, which is generally supplied in plastic sacks, delivered on pallets. A basic boiler – costing some £4,000 to £6,000 – will require you to tip bags of pellets into the top of it, and empty the ash from the bottom, much like any solid-fuel stove. This should be easy for younger people, but might not be ideal for more mature readers. More expensive versions – costing £10,000 upwards – can be sited in a garage or outbuilding and include a fuel hopper that can be filled with a larger quantity of pellets, blown in from a delivery tanker.
Note that wood-pellet boilers require an electrical supply, to power the auger that feeds the pellets into the combustion chamber, and to pre-heat the air supply for ignition. So they won’t work in a power cut.
Heating with wood pellets currently costs around 4p to 5p per kWh (“unit”), roughly the same price as gas, so scrapping your gas boiler and investing thousands of pounds in this trendy technology is unlikely to save you any money.