UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

Reed_Richards

In North America a lot of houses have "central air" through ducts to each room that blow hot air in winter and cold air in summer.  Unless you have the ducts or can manage to install them then with air-to-air heat pumps you need one unit per room, or something like.  It's a pity because only having to heat the air to the required room temperature makes air-to-air much more efficient than air-to-water. Oh, and no RHI on air-to-air.

I have an air-to-water heat pump which was installed about 4 months ago.  I only have radiators, no underfloor heating.  I got a new set of radiators when the heat pump was installed.  I had three quotes.  Two of the companies told me I would be saving money on my running costs compared to the oil heating that was being replaced.  One company told me there wouldn't be much in it and I went with that company because they seemed more honest; I have not regretted that decision.  

The heat pump and new radiators have kept the house perfectly warm.  After 4 months it is clear that my running cost will be comparable to oil, I am hoping a bit less but it is too early to be sure.  I'm a bit more optimistic about this than @matelodave , perhaps because my heat pump is newer and the COP should be a bit better.  It's not really about electricity prices and how they will change in future but how any changes in electricity prices compare to changes in the price of heating oil.          

matelodave

Mickey666 said:

matelodave said:

No,

it's an 11kw Daikin Altherma split ASHP which is heating an overlay underfloor wet system in a 140m2 bungalow together with a 200litre hot water tank

We actually installed it three years before the RHi came into effect so as far as I was concerned the RHI was a bonus rather than a consideration when we chose to have the heatpump.

Our RHI is based on a deemed COP of 2.5 and the EPC calculation, although I believe that nowdays the RHI is based on the calculated COP given on the MCS certificate and EPC heating calculation and is therefore worth more if the calculated COP is higher

The heatpump replaced eight manky rusty storage heaters (for which I dont have any cost info as we ripped them out the day we moved in) 

Fair enough, but a heat pump is always going to compare favourably with other forms of electric heating.  It's like going from a 'really expensive' form of heating to a 'quite expensive' form of heating and ignoring all the cheaper forms of heating available.

What was the cost of the installation and how long did it take to recover that cost based on your savings?

The supply and installation and commisioning cost of the whole system came to £14k of which the heatpump and associated hot water tank was £7.5k. The rest of the cost was for 140m2 of underfloor heating rather than radiators.. 

I guess that an oil boiler and associated tank together with underfloor heating would have been around £10-£11k. (we'd already decided that we wanted u/f heating rather than rads whatever the source) An LPG boiler probably would have been cheaper to instal as you end up hiring the tank but there's still the cost of a concrete plinth and piping as there is a with an oil tank.

My estimate for a "like for like" system is that the heat pump cost around £4k more than an oil installation and £5k more than LPG. We've actually just had £5k back fro the RHI so that's cancelled out the cost difference. Running costs are more difficult to compare as we dont have a before and after reference as we moved in and pulled everything out.

However if you assume that the EPC is anywhere close then we should have been using around 12500kwh for heating and 2500 for hot water = 15,000kwh. (the EPC dosen't include other stuff like washing, cooking TV etc). 

We actually use around 7200kwh of leccy a year for evrything and I guess half is for heating and half is for the rest , including hot water - our summer consumption is around 300kwh a month. (last year we used exactly 7199). We pay 12.25/kwh plus 13p s/c we are currently paying just under £1000 a year. Compare that with say 15,000kwh of oil at 4p/kwh (heating and hot water) plus around 3000kwh of leccy = £600 + £400 = £1000, so about on a par.

Anything else apart from mains gas (which we cant get) would have been a lot more expensive to run. You could do similar sums based on kwh costs for other forms of heating/fuels

We dont have a big tank in the garden nor tankers delivering (we have squadrons up and down our road at this time of the year) and mainenance costs are virtually non existent although the unvented hot water tank should be checked annually by a registered plumber, we've had it checked over three times in ten years..

I'd still have mainsns gas but it's not and never will be available where we live, so I reckon we have the best solution for us - it may not suit others but it works for our home all day lifestyle.

BTW we've had one problem with the heatpump since we've had it -  a sticking flow switch. Reported by the controller and I fixed it myself for no cost.

The u/f system has had two thermal actuators die but cheap and easy to replace at £15 each from Amazon (I've now got a spare, just in case but they dont stop the system from working)

RoyceCoolage

I am in the process of buying a house which currently only has night storage heaters for heating. I’m keen to get a better heating system in place ASAP, and gas/oil is not an option. As there is no wet heating system in the property I am leaning towards and air/air multi split system. Pros would be better efficiency than storage heaters, would do cooling in summer too, cons? There is a living room, office, conservatory and galley kitchen downstairs, and two bedrooms and a bathroom upstairs. There is currently a wood burner in the living room, but the chimney isn’t lined and I’m not keen generally on burners so would prob get chimney closed up properly.

I am going to contact contractors to see what they suggest but I wondered if any of you knowledgeable folk here have any suggestions or things to consider which I might not have thought of.

Thanks for any advice.

I am going to contact contractors to see what they suggest but I wondered if any of you knowledgeable folk here have any suggestions or things to consider which I might not have thought of.

Thanks for any advice.

Gerry1

Welcome to the forum.

IIRC an air/air system doesn't qualify for the Renewable Heat Incentive so the capital costs may be significantly higher than you were expecting.

RoyceCoolage

Thank you, and thanks for pointing that out, I had noticed it too. Honestly I haven’t got a firm idea on air/air instal costs so far. Because I would need to have a whole central heating system installed as well as an air/water heat pump to get the RHI, I thought the air/air costs might be comparable even without RHI because it wouldn’t need central heating on top. Definitely keen to get quotes for both (and other solutions?) and see what works out.

matelodave

Air to water would supply both heating and hot water from the heatpump whereas an air to air heatpump would offer both heating and cooling but not hot water so you'd have to use an immersion heater.

You have to use an heatpump during peak times, you dont get much benefit from an E7 tariff, E10 might be better if you can get it but you do pay the penaly of higher peak costs when on an multirate tariff. So hot water production would be cheaper with an air-water system than using an immersion heater

Potentially air-air could be cheaper to install than a wel system  but there is the possibility of planning problems if you have more than one compressor unit outside(a split sytem might help there) and there will be insulated refrigerant piping between the external compressor(s) and each of the room heat exchangers.
Another forumite pointed out the fact that RHI is paid to the owner of the system over seven years, so if you sell up within that time you wont benfit for the full seven years worth of payments

Its another situation where you've got to try and do the sums, not just for the short term but over the lifetime of the system.. You also need to take into account your lifestyle and whether you intend to stay in the palce for a decent amount of time.

There really is no right answer as each of us have our own views and priorities

danrv

I’ve just had an Aircon specialist round to give a quote for a system my 3 bed semi detached property.
£7-£8k approx. for 10kw ASHP and 5-6 indoor units. Quite a lot of money and would hope that it’d be very good.
I’d need to change my Economy 10 (electric warm air) to a cheap normal rate. 
Not too sure about the running costs with Aircon. I take it that the pump supplies the necessary power to however many indoor units are running.
Also unlike air to water, the heat would be more instant. 
Anyway, I’m considering it as an investment over storage heaters/electric rads.

richardc1983

danrv said:

I’ve just had an Aircon specialist round to give a quote for a system my 3 bed semi detached property.
£7-£8k approx. for 10kw ASHP and 5-6 indoor units. Quite a lot of money and would hope that it’d be very good.
I’d need to change my Economy 10 (electric warm air) to a cheap normal rate. 
Not too sure about the running costs with Aircon. I take it that the pump supplies the necessary power to however many indoor units are running.
Also unlike air to water, the heat would be more instant. 
Anyway, I’m considering it as an investment over storage heaters/electric rads.

Yes, the outdoor unit will supply the power to the indoor units. You will obviously benefit from the cooling in summer so it's a good investment. 

Get a couple of quotes though.

Jeanbuchan

Be very careful before you choose an air to air heat pump.  We installed one in 2013 at a cost of £9,500.  We thought it was a good buy and it was definitely a lot cheaper to run than our old storage heaters.  Five years later it stopped working and the company went into liquidation.  As we had paid in full at the time of purchase, that was it for us, even though it was guaranteed for ten years.  We had to have a specialist come to extract the units because of the gas. 

richardc1983

Jeanbuchan said:

Be very careful before you choose an air to air heat pump.  We installed one in 2013 at a cost of £9,500.  We thought it was a good buy and it was definitely a lot cheaper to run than our old storage heaters.  Five years later it stopped working and the company went into liquidation.  As we had paid in full at the time of purchase, that was it for us, even though it was guaranteed for ten years.  We had to have a specialist come to extract the units because of the gas. 

What brand was it? All the big companies are going no where. Was it the installer who went bust as any reputable fgas accredited and registered company can work on these provided they are fgas registered.