Heat pump with stoves

[CharlieB]

Seems made to ask about heating right now, but there we are. We’ve moved into an old 4 bed farmhouse in a scotland. Lovely at this time of year, and the fact it’s generally cooler inside than outside during the day suggests it’s got good high thermal mass. It’s currently heated with oil from a tank, plus a wood stove and an open fire. Single glazed.

I’ve looked at woodchip or log boilers and decided they don’t really make sense. Pellet might, but the big upfront cost is an issue as we don’t own the house. Gshp similarly high upfront cost, so I can’t help wondering about ASHP, especially as my friendly local renewables installer (KennyT, who used to be on the other forum) said ASHP is easy and GSHP a massive hassle for him.

I know big drafty houses without undferfloor heating are the classic not-suited-to-heatpump homes, but if we just accept that we’re living in an old house and expect the heat pump to keep the chill off rather than heat to a comfortable temperature might it be a go-er? Especially as I could put a large stove in a central location which would heat upstairs, and already have two other stoves in main living spaces. Over time we would replace existing relatively small radiators with double or triple sized ones and possibly even fit underfloor heating upstairs, but for now it would more or less be taking oil boiler our and replacing with heat pump.

So, some questions:

• Does anyone have experience of ashps doing bare minimum heating with wood stoves doing significant top up?

• I realise the COP won't be brilliant, especially in the winter, but this (ashp plus wood) still feels like a greener option now than oil. Agree?

• Even if we're trying to run the ASHP too hot and we end up using electric radiators a bit to top up heating (ie if working from home), do you reckon running costs will be higher or lower than the oil?

• What's your guestimate on size of heat pump needed? 4 beds, but a big downstairs with 2 living rooms and a dining room as well as kitchen. One living room is a badly built 1980s extension

Thanks all. Any thoughts welcome. For now I'm just contemplating. (And I realise the mantra is insulate, insulate, insulate. We'll be doing that too, over time.)

Charlie

[Stinsy]

You ask a lot of questions that we cannot accurately answer. I'll try to give you a few snippets that will hopefully be helpful.

• Woodchip or pellet boilers require a lot of maintenance and you're reliant on being able to get a reliable supply of fuel for a reasonable price

• Log burners, particularly those with "back boilers" tied int your hydronic heating system can work very well if you're around to light/feed it.

• GSHPs cost a fortune to install, most people never see that money back. If you're building from scratch or doing a very extensive renovation, so already have an excavator and its operator on site then you can dig a trench for a slinky while you're at it, which is much more economical.

• An oversized HP idling along will use less electricity than an undersized one running flat-out.

• Resistive heat the most expensive way to heat your home unless you're using cheap-rate electric.

• Oil has historically been much more expensive than town-gas and on a par with ASHP/Bottle gas. Oil is currently very expensive, you're guess is as good as min what will happen in future.