Yep, I've had a wood pellet boiler since Feb 2014 and have an ETA PU15, plus solar thermal panels.
Pros:
* this particular boiler has very capable and adaptable software which act as a mini building management system so can work with other equipment easily. It controls my solar hot water rather than having a separate controller, enabling it to prioritise the solar. Can also work with other boilers, i.e. the biomass runs as lead boiler but have top up or back-up heat from a conventional oil boiler for example. It can also handle zoned circuits with different flow temperatures to account for mix of underfloor heating and radiators.
* 7 years of renewable heat incentive income will pay back approx 70-80% of the capital cost in my case.
* mine has automatic vacuum feed of pellets from a 4 tonne pellet silo in the garden (max. vacuum feed length is approx 20m for my boiler)
* Boiler has internet connection (hard wired to a powerline adaptor) so I can do full remote control if required. Service engineer is also set up to view it if required to investigate faults/issues. However, many boilers now have some similar functionality.
* unlike an alternative heat pump solution I didn't need to increase radiator sizes to compensate for lower flow temperatures.
* very efficient and produces little ash. The onboard ash box is about the volume of a couple of shoe boxes. Even in the dead of winter I only have to empty it every few weeks. Probably don't empty it more than 8-10 times a year. Ash goes on the garden.
Cons:
* complexity of software is not for everyone. Fine for me, as I fine tune it throughout the year.
* boiler needs to be sized carefully for the house, as you can't just turn it on/off like a gas boiler every few minutes. Consequently, if the house is really cold it takes a long while to get the temperature up. Accordingly, instead of switching off at night I set back the target temperature a couple of degrees and start it back up to day target temp from around 05:30 to give it a chance to get up to speed. Summary - not particularly responsive.
* servicing costs. I wish I'd known more about this. It costs me around £450 a year for an annual service, plus any unexpected parts. This is fine while you're getting quarterly RHI payments but when they run out next year it's quite a cost.
* I've had flue problems with mine - poor design, although installation options were limited.
* slight smoky smell, particularly in windy weather when you might get a bit of backdraught into the flue. Recommend boiler is in a utility room where you can shut the door, or out in a garage.
* pellet costs, when I installed the boiler, would give delivered heat cheaper than oil. That is not currently the case, although again the RHI does compensate a bit for this. I only need a fill up of the silo (4 tonnes) once a year, which costs around £1k for an older property of approx 155m2 heated floorspace.
Would I install another one? Thoughts:
* since I installed mine, the sustainability of wood pellets has undergone a revision in thinking and the environmental case is probably a bit weaker, especially as the electrical grid cleans up. Nonetheless, the latest DEFRA emission factors for GHG reporting still show a significant benefit in using wood fuel. My purchase was very much driven by environmental concerns so I definitely wouldn't revert to an oil boiler.
* ongoing service costs, additional fuel running costs (compared to current oil prices) and the space required for a pellet boiler/silo are significant downsides.
* For an older property like mine, which isn't ideally suited to economical use of an air source heat pump, I would probably now install a hybrid heat pump/oil boiler system so that the heat pump tackles base load for most of the year and the oil boiler kicks in to deal with higher temperatures. However, such things weren't readily available 5 years ago, and even now the installed market is limited.
* initial capital cost was eye-popping. More recently, the RHI scheme was amended to allow the RHI payments to be assigned to a third party which has opened up the market to funded installations which overcomes some of the hurdle for homeowners.
*I'm not planning on moving house any time soon, but if I was I would have concerns about whether the heating system might put off some potential buyers a bit.