Hi! We are likely to be in a similar position. I’ve not sat and looked at the actual £/p of changing from our current gas combi to a heat pump; but we only use c. 3,000 kWh a year gas (hot water and heating). I’m pretty sure whatever heat pump we get is likely to end up costing us more in running costs. Currently in discussions with our Heat Geek re sizing / design. My suspicion is that our house is much better thermally performing than (even his very extensive!) survey predictions; and the MVHR and insulation mean that we ‘feel’ warmer even at a lower temperature than the ‘usual’ 21 deg. I honestly think we are happy at 18-19 deg; but hard to be certain: we certainly don’t need/want our bedrooms at 21deg (or the kitchen for that matter, north facing, and if you’re cooking you’re on your feet and creating heat to boot).
For very low consumption systems you would probably be better off with a very small A2A system. That also gives the option of cooling in summer, or even when throwing a party. It wouldn’t qualify for a grant but should be significantly cheaper than a small A2W with BUS grant.
Doesn’t fix domestic hot water though, and we already have wet underfloor heating.
@Giselle_du_Toit, I didn’t welcome you to the forum, so belatedly, Welcome.
You are clearly committed to wet heating but as a general rule my response above is true. You would however need an alternative DHW solution, of which there are several to choose from.
So again, generally speaking:
If you have instant hot water now you will need to find an alternative anyway if going to an A2W heat pump. The only choice when going for a BUS grant is to heat water via the heat pump but otherwise the array of choices can be quite daunting, particularly if your hot water requirement is quite low and can be satisfied by overnight heating and storage.
Thanks Tim. Not sure what the alternatives for DHW are, aside from straight immersion electric into a (new) cylinder; or something like the Sunamp Thermino (which I’ve gone off of entirely after reading about catastrophic failures). Am I missing anything else? Solar thermal won’t work year round; and I don’t think our roof is suitable for solar PV; although am tempted to ask someone to come out and confirm. We have an electric shower in one largely unused bathroom and are very underwhelmed.
Off the top of my head there are:
Cylinder via general HP
Cylinder with dedicated DHW HP
Cylinder via immersion only
Sunamp models and similar
Tepeo models, particularly ZEB
Electric instant hot water centrally
Electric instant hot water at point of use
Solar thermal (which I have in addition to my HP)
Geothermal (but not in the UK)
(Anyone got more suggestions?)
Edit:
Other electric boilers (not Tepeo or similar)
Direct PV to immersion heater
So, if using a Sunamp heat battery (+some PV) for hot water, is the BUS grant not available for ASHP for central-heating-only use?
…what are these pl?
The BUS grant is to fully replace your boiler. That is somewhat open to interpretation. If there is no link from your current boiler to your DHW system you could give it a try.
In my case I had a redundant connection to my hot water cylinder and that had to be replicated but the installers said that had I removed the connection first I MIGHT have got away with it.
My previous DHW setup, reflected on my EPC, was primary heat source solar thermal and secondary immersion heater (used off peak).
My current DHW setup is still primary heat source solar thermal. Even in winter that keeps my cylinder at about 20°C or more, so reduces the need to expend energy reaching the target temperature, then I use the heat pump to increase the temperature to mid 40’s °C and finally the immersion for any top up.
Instant electric hot water is basically supplied by a dirty great heating element in your hot water that triggers when water flows, a bit like an old gas Geyser. The hot water component of a Combi boiler does the same.
If centrally supplied you have one heater set back in your system so that whatever hot tap is opened it triggers. The appliance needs enough kW to heat multiple outlets simultaneously. Water left in the pipes between heat source and tap cools and the energy is lost.
Distributed instant hot water is similar but with a heat source at each outlet (or you might have one in the bathroom to cover both wash basin and shower). The most common occurrences are electric showers but there are others like electric taps or under sink units. There is negligible energy lost in the system but usually there is considerably more work and outlay involved. These systems are typically installed in properties with excessive pipe runs.
My most recent place of work has under sink units dotted around the washrooms and staff rest rooms.
Aha…didn’t know about all that, esp electric taps etc. Electric shower I know, obvs (my partner leans towards keeping ours, if we move to ASHP, on a just-in-case basis…!)
What is the higher of the temperatures you shower at and can your electric shower accept prewarmed water?
I shower at 37-38°C. Mrs. G. normally leaves the thermostatic mixer at Max, whatever the temperature of the hot water, which can get extremely hot in summer.
Clearly 37-38°C is comfortably within the range of a heat pump but getting to Mrs. G.’s preferred temperature would be pushing it. Hence the immersion top up. This is where your electric shower could take up the slack, if it has that ability.
I’ve gone off sunamp after reading a thread about catastrophic failure on build hub