Air to air or air to water?

ed110220

OK I realise this is a pretty open ended question but what are people's thoughts on air to air heat pumps (basically split air conditioners) v air to water?

I've recently installed a home battery and switched to Octopus Go, so the large majority of our electricity consumption is at 8.5p/kWh, averaging about 10p/kWh. Our house is heated by gas central heating with a combi boiler. It's fairly well insulated, we use about 6000 kWh of gas per year. The house is pretty open plan downstairs and even upstairs the rooms tend to stay at a similar temperature when I have the CH off but the dehumidifier on which kicks out a bit of warmth because we leave the doors open. Not sure if our radiators would put out enough heat at lower flow temperatures. We have one radiator and one hydronic plinth heater downstairs and two radiators and two plinth heaters upstairs (not much room for radiators so I replaced some with plinth heaters in the base of built in cupboards).

So I'm tending towards A2A, maybe starting with one unit downstairs, as cheaper and more efficient than A2W. On the other hand it wouldn't do DWH but perhaps that's not so much of a disadvantage?

subjecttocontract

We have a property in Spain and had an additional air conditioner installed (Siemens) which was a split air to air unit. Obviously in summer when it's unbearably hot the air con works brilliantly. I am astonished at just how good it is at pumping out heat during the colder months when it can get down to 3 or 4 degrees in the evening. It doesn't seem to use a lot of electricity, we don't notice any extra cost but we only have it running for a few hours each evening. Certainly recommended. I understand that you can now get these in the UK (e.g. from Mitsubishi Heavy Industries, Daikin & others) where a single external unit can be piped in up to 4 rooms.

QrizB

There are a couple of recent threads on A2A heat pumps:

https://forums.moneysavingexpert.com/discussion/6570763/air-to-air-multi-split-heat-pump-bungalow-without-boiler-radiators

and

https://forums.moneysavingexpert.com/discussion/6574532/air-to-air-heat-pump

Rodders53

A fair cost investment (circa £1k+?) for relatively little cost difference in heating (gas 6.4p/kWh vs 2.5 p /kWh if you can get a COP of 4).

Now if you want AirCon and can afford the capital expenditure go for it.

We have some for that purpose (bedroom in summer) and with oil fired UFH with awful laggy temperature hysteresis they are used frequently for heat in the shoulder months (rather than oil) and even for a short 'boost' if we feel chilly, like last night.

They are like glorified fan heaters, but quieter and a lot, lot bigger.  If you have no room for radiators you may struggle to find room for the indoor units.

In theory one need Planning Permission for A-A heat pumps.  A-W will often come under Permitted Development.

subjecttocontract

Rodders53 said:

A fair cost investment (circa £1k+?) for relatively little cost difference in heating (gas 6.4p/kWh vs 2.5 p /kWh if you can get a COP of 4).

Now if you want AirCon and can afford the capital expenditure go for it.

We have some for that purpose (bedroom in summer) and with oil fired UFH with awful laggy temperature hysteresis they are used frequently for heat in the shoulder months (rather than oil) and even for a short 'boost' if we feel chilly, like last night.

They are like glorified fan heaters, but quieter and a lot, lot bigger.  If you have no room for radiators you may struggle to find room for the indoor units.

In theory one need Planning Permission for A-A heat pumps.  A-W will often come under Permitted Development.

If you have a solar installation then A2A can work out very cost effective......sometimes free. Even in the depths of winter when temps are way below freezing we have very sunny days that provide free electicity. It's always worth considering that normally the cost of electricity is around 4 times that of gas per kwh.

ed110220

subjecttocontract said:

Rodders53 said:

A fair cost investment (circa £1k+?) for relatively little cost difference in heating (gas 6.4p/kWh vs 2.5 p /kWh if you can get a COP of 4).

Now if you want AirCon and can afford the capital expenditure go for it.

We have some for that purpose (bedroom in summer) and with oil fired UFH with awful laggy temperature hysteresis they are used frequently for heat in the shoulder months (rather than oil) and even for a short 'boost' if we feel chilly, like last night.

They are like glorified fan heaters, but quieter and a lot, lot bigger.  If you have no room for radiators you may struggle to find room for the indoor units.

In theory one need Planning Permission for A-A heat pumps.  A-W will often come under Permitted Development.

If you have a solar installation then A2A can work out very cost effective......sometimes free. Even in the depths of winter when temps are way below freezing we have very sunny days that provide free electicity. It's always worth considering that normally the cost of electricity is around 4 times that of gas per kwh.

Thanks, I do have solar. I also have battery storage so on Octopus Go the cost of electricity at the moment is not much more than gas per kWh (8.5p v 6.62p ) and that's before considering the COP of a heat pump (and the negative COP of a boiler).

I'm pretty sure air to air would work well, the main question is whether it's worth going for something that heats the hot water too.