Number 1 thing I would want to know is about costs. What are the comparative costs for replacement boiler vs new install ASHP over 5 and 10 years? Installation and any other work needed to make everything work at its best, plus ongoing running costs for 5 and 10 years, based on today's energy rates would be good enough. At what point would we expect to break even? And any subsidies available and how that affects those figures.
I want to do it for the environment, but it also has to make financial sense and be developed enough to do the job it's meant to do. What I've heard about most is that it can struggle to keep the house as warm as a gas boiler system. I'm willing to wait a bit if the technology is developing fast atm.
Number 1 is cost. with a gas boiler and moving it was £4k. With a green energy loan over 10 years (interest free)and RHI for 7 years. it works on a 60/40 in favour of ASHP. RHI is not much. It was £203 this year.
To give better value a pellet boiler may have given me more. However you need space for the boiler and the auto feeder and the sacks of pelletts.
Who knows which is better value for money. Problems are few and far between. Serviced often and keep the pipes well insulated and you can save.
This months gas bill and usage. In the summer with solar panels as well , i only pay the service charge.
| 869.27 kWh at 2.95p | £25.64 |
Thank you for that. My cooker is almost 20 years old, so it wouldn't be an issue to drop the gas (hob only) and go induction hob, so we'd be able to drop gas and the standing charge all together so there's that saving as well.
When we had the solar installed they gave us projections for when we'd be breaking even, that's something I'm interested in for ASHP. I know the projections were exaggerated by some installers but we've kept an eye on it and it's been about right.
Benefits: They reduce the amount of CO2 you're responsible for. Obviously the way the country's electricity is generated has an impact on this but the country is gradually moving to lower carbon electricity.
Disadvantages:
Cost. They're expensive, even with govt subsidies. There's an argument that the subsidies actually increase costs but that's probably a debate for a different thread.
Controls: They're too complicated. I've seen lots of discussion about compensation curves, flow temperatures, target temperatures etc. While the geeks among us might be happy playing around with the heat pump settings to get the best out of it, Jo Public just wants a system that works. The controls and user interfaces need to be better.
Response: We're all used to being able to switch a gas boiler on and the house heating up quickly. You can't do that with a heat pump. This means you need a different way of thinking about your heating.
I haven't mentioned running costs yet. One of the first questions everyone asks is if it's cheaper to run than a gas boiler because we're conditioned to expect new stuff to be cheaper and/or better. The answer is "maybe". Some people find a heat pump is cheaper to run. Some find it's more expensive. For various reasons I can't tell how mine compares.
Some great insights being shared already, both from those with a heat pump already and a prospective ASHPer, @Gum168 !
And a clear theme emerging in terms of what might be the biggest factor to consider:
Number 1 thing I would want to know is about costs.
So cost (as expected) is the big one!
Really interested to hear more about this green loan, @Heatherd - Was this a government-backed loan or via a bank or other lender? How did you go about calculating the cost-difference to a standard gas boiler replacement - Was this straight-forward or would you recommend seeking out professional advice on this one?
What I've heard about most is that it can struggle to keep the house as warm as a gas boiler system.
This is another common concern, @Gum168 - after all if you might be incurring higher costs you’d want some reassurance that you’ll be kept nice and toasty as a result. Hoping this is one for our ASHP trialist to clear up, @juliamc, @Bell, @PHILLI2, @Buriton57 - How would you compare the heat output or home comfort levels since getting your gas boilers replaced for an ASHP?
So these companies that fit the ASHP put you in touch with people who can help you fund it. mine was the energy funding trust. They give you a loan over 10 years (mine is £38.30 a month for £5700.
I have a hybrid system Diakin altherma , half ashp half gas. When house starts to warm up off ASHP it takes ages as it does it slowly. No piping hot radiators. just constant heat. Mine is set on 40% gas 60% ASHP. Heat wise it is thee same., just takes longer. During the day is fine when it is during thee summer as costing me nothing with solar. In winter my electric goes to £57.82 from 0, my gas is £29.74. plus all service charges.
Ah, interesting, I didn't know there are hybrid systems like that, I assumed any top up heat is from other electric heat sources.
We are in a rural area and there are many villages that don't have gas and we are the last village to the west of Hull that has does. So with the price of oil I know that many in the further out villages are looking into ASHPs. However the local heating engineer who does our servicing said he's not yet convinced that they are quite up to the job yet. He said wait a few years if the boiler is OK.
So, quick question, how is hot water heated? Due to the solar we use the electric immersion element in summer, and gas in winter. TIA.
A heat pump will heat your hot water. It doesn't heat it to as high a temperature as a gas boiler but it will get it hot enough for all domestic use. Most people have a larger hot water tank to compensate for the water being at a lower temperature.
Thank you, that's useful information from both of you.
@M.isterW has summed things up nicely.
For me now running costs are comparable to when I had gas before but it took a change in mind set from heating the house on demand, to heating the house slowly but continuously.
Is your house suitable? More houses than not are suitable I think is an initial opinion from this heat pump trial but, and it’s a big BUT, the systems HAVE to be installed well, my experience proves that. A reputable installer will work out whether a house is suitable and provide estimates of energy usage. If they don’t spend an hour or more calculating this before providing a quote then they are taking short cuts.
The industry needs to wake up to the poor installation standards seen in some examples before it ruins (perhaps unfairly) the reputation of heat pumps.
But regardless of what type of heating system you have, do your best to insulate your property and reduce your energy wastage. It’s more apparent with heat pumps because the energy source is more expensive (currently) but the energy wastage is still there with gas, oil, lpg boilers, it’s just not noticed because the energy source is (currently) much cheaper.
Excellent forum discussion and real life experience indeed.
One thing your installer will likely discuss with you is efficiency and effectiveness of your home insulation. This may mean different things however if you’re using rads then it is likely they need to be upgraded (i.e. bigger!) to compensate for the extra heating surface required for the low water temperature for heat pump.
I would suggest plan for around £300 to £450 per rad incl installation excl the fancy designer ones in home magazines.
This is our first winter with ASHP and I can already see my electricity bill higher to my last year gas+elec monthly bill combined. Now, I am discounting the increased gas price which may favour the almost zero gas cost and much higher electricity cost. We are not yet in full winter yet so holding my calculations for now.
I was bored so I worked out a cost comparison between Dec last year (gas heating) and Dec this year (heat pump). I'm going to put a bunch of caveats on this.…
1 - I only have average usage figures for Dec 21 as I didn't have a smart meter.
2 - We have a Phev so I've assumed we charged it the same amount both years.
3 - Our heat pump setup is a bit odd so some of our hot water comes from an immersion heater. That's increased the Dec 22 electricity use.
4 - I've calculated the usage and worked out the costs at Dec 22 prices.
Dec 21 - £166
Dec 22 - £177
I can't remember if Dec 21 was warmer or colder than Dec 22 but I think this shows that the running costs are comparable.
I can't remember if Dec 21 was warmer or colder than Dec 22 but I think this shows that the running costs are comparable.
If you can accurately predict the weather and energy prices for December 22 then I think lots of energy companies will be clamouring to give you a job! 
I can't remember if Dec 21 was warmer or colder than Dec 22 but I think this shows that the running costs are comparable.
If you can accurately predict the weather and energy prices for December 22 then I think lots of energy companies will be clamouring to give you a job!
Well, I messed that up. Let's go for Dec 20 and Dec 21 
I can't remember if Dec 21 was warmer or colder than Dec 22 but I think this shows that the running costs are comparable.
If you can accurately predict the weather and energy prices for December 22 then I think lots of energy companies will be clamouring to give you a job!
Well, I messed that up. Let's go for Dec 20 and Dec 21
From the met office website. There may be other organisations calculating different averages.
UK mean temperature for Dec 2020 was 4.3 degrees they say
UK mean temperature for Dec 2021 was 5.3 degrees they say
Differences do vary by region. Also particularly cold times and wet days will have an impact i assume on heating costs
Quite difficult to compare but non the less positive that for this particular home the heat pump setup isn't significantly more expensive in terms of running costs so far.
If this is around the average increase in cost then i think that is positive. I am expecting the price cap review to increase gas prices more than electricity prices so the 2020 vs 2021 comparison may look very different. It sounds like the price cap will be announced around the 7th Feb ready for the change in April.
https://www.metoffice.gov.uk/research/climate/maps-and-data/summaries/index
I was bored so I worked out a cost comparison between Dec last year (gas heating) and Dec this year (heat pump). I'm going to put a bunch of caveats on this.…
1 - I only have average usage figures for Dec 21 as I didn't have a smart meter.
2 - We have a Phev so I've assumed we charged it the same amount both years.
3 - Our heat pump setup is a bit odd so some of our hot water comes from an immersion heater. That's increased the Dec 22 electricity use.
4 - I've calculated the usage and worked out the costs at Dec 22 prices.
Dec 21 - £166
Dec 22 - £177
I can't remember if Dec 21 was warmer or colder than Dec 22 but I think this shows that the running costs are comparable.
Be curious to know the number of kWh for gas in December 2020 vs the number of kWh for electricity in December 2021
Are the numbers you quoted what you estimate just for heating and hot water?
On my tariff the unit rate for electricity is 5.56 higher than gas but i doubt i will ever see that again
Some really great points being raised here both by prospective AHSP owners and those just getting to grips with their new ASHP setups.
Just wanted to tag a new arrival to the community, @Adam Vetere - as they’ve also mentioned an upcoming heat pump installation. How do your pre-installation questions/concerns match up to what already been discussed here, @Adam Vetere?
Anything you’d like to ask those who have already been through the installation process? 
At this time it is more expensive running a heat pump than the combined gas an electric a year ago. This maybe due to the complete lack of control we have being part of the Heat Pump trial and the system being controlled by someone else. If we were able to heat the batteries using cheap off peak electric or solar PV this might inverse the cost. The sunamp batteries seem to be inefficient for hot water, always relying on an immersion to get the hot water to a useable temp. We also have a major situation with where the heat pump was installed as it now blasts our outdoor deck area with ice cold air, it was not ‘allowed’ to be more than 10 meters from the house.
The comment from @hambrook demonstrates how important it is to get the specification and installation right. We have almost identical systems as we're both part of the same trial. Mine heats the house very well, is located down the side of the house and, despite some of the water being heated with an immersion heater, is costing about the same to run as our old gas system.
At this time it is more expensive running a heat pump than the combined gas an electric a year ago. This maybe due to the complete lack of control we have being part of the Heat Pump trial and the system being controlled by someone else. If we were able to heat the batteries using cheap off peak electric or solar PV this might inverse the cost. The sunamp batteries seem to be inefficient for hot water, always relying on an immersion to get the hot water to a useable temp. We also have a major situation with where the heat pump was installed as it now blasts our outdoor deck area with ice cold air, it was not ‘allowed’ to be more than 10 meters from the house.
Did you use to heat your domestic hot water with solar PV and/or off peak electricity prior to the heat pump trial?
The comment from @hambrook demonstrates how important it is to get the specification and installation right. We have almost identical systems as we're both part of the same trial. Mine heats the house very well, is located down the side of the house and, despite some of the water being heated with an immersion heater, is costing about the same to run as our old gas system.
It is also complicated by the fact that we don't know if your pre trial setup was more or less efficient than that of @hambrook
Your pre trial setups may not have been identical, so the delta in costs may be different between old and trial setup.
Putting aside the issue with the position of the pump.
The comment from @hambrook demonstrates how important it is to get the specification and installation right. We have almost identical systems as we're both part of the same trial. Mine heats the house very well, is located down the side of the house and, despite some of the water being heated with an immersion heater, is costing about the same to run as our old gas system.
Great comment. I think the EPC is a blunt tool to base a Heat Pump install by. Our home had a B rated EPC. It does not provide room by room insulation recommendations. The company that did the install asked me for all the room sizes and I can not see how the doors, windows were correctly captured to produce the BTU numbers. The one Climavent Radiator in our kitchen dinner can not heat that room even if it was on 24 hours a day, so where did the BTU calcs / survey fail?
For our house we have rooms with 2, 3 or 4 external walls and whilst this house has cavity wall insulation, A-rated windows, loft insulation, the Heat Pump can not produce the heat to off-set the losses. I would love to to know how to externally clad and render this house? Are there grants to do this work? I think some ‘follow up / snag list’ would be good as well/ For instance we had to replace a single panel existing radiant in a downstairs loo as it never got warm after the heat pump install. Towel rails also only get Luke warm rather than hot
Great comment. I think the EPC is a blunt tool to base a Heat Pump install by. Our home had a B rated EPC. It does not provide room by room insulation recommendations. The company that did the install asked me for all the room sizes and I can not see how the doors, windows were correctly captured to produce the BTU numbers. The one Climavent Radiator in our kitchen dinner can not heat that room even if it was on 24 hours a day, so where did the BTU calcs / survey fail?
For our house we have rooms with 2, 3 or 4 external walls and whilst this house has cavity wall insulation, A-rated windows, loft insulation, the Heat Pump can not produce the heat to off-set the losses. I would love to to know how to externally clad and render this house? Are there grants to do this work? I think some ‘follow up / snag list’ would be good as well/ For instance we had to replace a single panel existing radiant in a downstairs loo as it never got warm after the heat pump install. Towel rails also only get Luke warm rather than hot
That is a shame.
In theory an MCS accredited installer should have done a proper room by room assessment themselves.
They shouldn't be making any reference to the EPC. The EPC is irrelevant. The only reason the EPC is needed is for the RHI payments. It has nothing to do with the heat pump related calculations.
I would hope there is some sort of on site independent audit of installations as part of the trial to capture lessons learned?
I would hope there is some sort of on site independent audit of installations as part of the trial to capture lessons learned?
I would LOVE their to be an audit of my installation by BEIS or Mitsubishi
