By Khalid Aziz
What about a wood pellet boiler?
That was the question put to us in 2011 by our visionary plumber when we started serious renovation of our property in St Mary Bourne. Having been almost lifelong rural dwellers we had always relied on oil. We looked at air and ground source heat pumps as an option (mindful even then of being a good citizen of the Earth, years before people started blocking bridges in London) but unless you have a modern house with modern insulation that was a no-no.
Oil is not sustainable. Once you have pumped it out of the ground and burnt it you have to pump some more. What’s more the burning creates carbon dioxide which, along with methane from cattle (and us!), is responsible for heating up the planet. Burning wood pellets creates carbon dioxide too but the theory is that this is absorbed by the trees replanted to grow the wood to make more pellets.
In 2011 the oil price was pretty high. Pellets looked attractive. The government was also dangling a carrot - something called a Renewable Heat Incentive (RHI) - a subsidy, due to be introduced the following year and back dated to any new installation - pellets looked even more attractive.
In Austria no new-build could be heated by oil at that time (and ever since) and they have pioneered wood pellet boilers as a cheaper alternative to electrical heating. It made sense, therefore, that we bought an Austrian boiler - a Windhager. Wood pellet heating was and is In the UK very much down to personal choice but there was always that subsidy. So we took the plunge. It was a heavy investment. We might have spent £2000 on a new oil boiler; the wood pellet burner was more like £12000. But pellets were around £180 a tonne delivered and as a fuel then looked much more attractive than oil in terms of running costs.
We heat two buildings from the one pellet boiler – the main house and a nearby cottage – a total of seven bedrooms and the equivalent of 9 reception rooms. It was convenient to locate the boiler in an adjacent barn which also housed the silo for storing pellets. With a capacity of 11 tonnes it’s large but it means just three pellet deliveries a year. Of course, you can store smaller quantities of pellets but that means more deliveries. Hot water is delivered to each building via buried, super-insulated umbilicals.
Has it worked? Well, the boiler has been pretty much trouble free. It needs servicing once a year - around £300 – which I believe is more than an oil fired boiler. We have had to have one part replaced – out of warranty, naturally. The boiler produces relatively little ash - it’s so efficient - which you empty every 5 or 6 months. Other than that, it is reliable.
However, pellet costs seem to be on an ever upward trajectory and the last delivery was around £250 a tonne. At the moment the subsidy just about covers the costs of the pellets but I was rather hoping I might get some contribution to the capital cost of the boiler. There seems little linkage between the price of oil which (as I write in October 2019) is relatively cheap and the cost of pellets. With only two importer/producers of pellets in the country I am not convinced the market is that competitive.
So if you are thinking about a wood pellet boiler do your sums. Boilers may well have come down in price. The technology is certainly proven. However, you are locked into pellet suppliers and there is little opportunity to shop around. Also, I am not sure of the government’s continuing appetite for RHI. However, a good friend looked at my system and installed something similar in his Scottish home supplied by wood from his forest converted in his own pelletising machine. That means the energy is cheap but you will need an extra few hundred acres!