Paul as kezo says i have a large house and I’m based between Glasgow and Edinburgh so have a high gas bill at the moment hence the anticipated move to an ASHP. My gas usage last year was 16,500 kWh f or heating and hot water. I plan to keep my combi boiler for hot water and as a safety net in case the ASHP turns out to be a bad move. There are a couple of options to reduce the pump size but I’m not sure it would make a huge difference. I have 200mm of loft insulation that i could easily increase. I have sprayed insulation to my entire downstairs so that’s fine. My windows are all double-glazed but very old. The two main living space windiws are both 2.4m x 1.8m so i could maybe reduce some heat lose by changing the glass units to Argon-filled. I have a mate who owns a glass company so this could be an option. The house has cavity wall insulation on the existing section and timber frame with 75 mm thick insulation on the extension. So there’s a couple of things i could do and might yet do but I’d probably be tinkering around the edges. What size of ASHP do you have Paul and what has been your experience with it?
Unfortunately Kezo, has advised incorrectly here.
I am based Nr Hamilton so not a million miles from you.
What is the m2 of the property and what is showing as your primary energy indicator on your EPC?
For example here is mine from our property and next doors to us for comparison.
Our house is substantially extended from next door so is bigger in size,
The heat loss from our neighbours is 208 kWh/m2/year
Our heat loss with the house extended is -23 kWh/m2/year
As you can see a substantial difference between 2 properties in the same location.
We kept the gas boiler as a back up, our ASHP is an Ecodan, and it is set to 22 and is only really in use from November till February it runs around 1-2 hours per day maximum some days during this period it does not run at all.
Our ASHP has actually become oversized now, due to the minimal heat loss of the property, we have also had A/C also a heat pump installed to cool the property as is so warm especially when going to bed as heat rises, our a/c in the bedroom runs overnight even all through winter.
As you can see from the Octopus graphs we are a net exporter and only import from the grid November – February at 7p per kWh but sell at 34p per kWh
Our gas usage which is hot water only is 2900kWh around £115 per year on Octopus gas tracker tariff
We took on a project of insulation in 2022 with the solar pv with Tesla PW’s and MVHR system going in with ASHP, the entire house was insulated to passiv house standards following the Enerphit guidelines, as a result we are now a zero bills house.
Last year all our energy costs minus the grid import and standing charges resulted in a credit of £1567.33
We know we undertook quite a challenge, our first point that we did before planning any of our project was to have a blower door test, this was a great eye opener to areas we never considered to be an issue, I would also recommend a thermal image survey.
As you can see it can be done and I wish you well on your heat reductions