Heating options alongside solid fuel

drsquirrel

We initially started with oil fired central heating, and then added 2 wood stoves in the main rooms. We get a good amount of wood from the property to run these, but not enough to consider heating the house and water with a back boiler.

The house is decently insulated (double glazed, loft, cavity etc), and we only used ~300L of oil last year - granted it was very mild! The year before it was ~700L with only one wood burner installed.

We're finding problems, or at least the heating engineer keeps complaining about it, that the oil boiler isn't running hard enough and thus is not running as efficient/condensing.

Now I can understand why running it harder (colder return temps) makes it more efficient but I find it hard to justify using more fuel just to do so. We have tried to schedule the system to rely on the oil more in the morning to get everything up to temp (thus running most the rads on start up), and then wood from the middle of the day as and when needed. Though this will miss the bedrooms later on in the day if it doesn't come on, and will end up losing some of the morning heat too, as its a bungalow (~110sqm).

We have individually programmable TRVs (so each room is its own zone if we want), so we can heat just the bedrooms later on, but this comes back to "not running it hard enough". Which, as I have seen, is causing the turbulators to gunk up a bit nearer the exit of the condenser (which is also eating away at the aluminum). Ideally we'd like to heat rooms as and when we want them.

The other idea was to heat hot water at the same time. With this we're very organized about our schedules and only run it when we need it which isn't as often as the heating (we have a modern stainless hot water tank). There are hot water solar panels ready to go up at some point which will dig into this as well.

Are we being lead astray on this "not being run hard enough" thinking? Are gas condensing boilers similar?

I've been looking into possible alternatives. I've always felt that considering the cost of boilers, rads, and wet system maintenance that in very small places electric (wall heaters) is easier and probably cheaper. Though in this place I do not think it would be suitable unless we had more wood fuel (without cost) and a back boiler.

Started looking at the likes of GSHP but the very high costs up front, the amount of space they take I am not convinced this will ever have a decent ROI (anything under 50 years...)

I know it is usually the worst option, but I feel that an electric central heating boiler might even worse. I am not 100% on their workings but I'd imagine they're 100% efficient at the boiler (same loses through the wet system sure), and even if it was running one radiator at a time it wouldn't have any problems?

Any thoughts, ideas, suggestions?