Willis heater ASHP backup discussion

[Ed Davies]

47 minutes ago, ProDave said:

At that usage, if the temperature was 0 all year, the heating bill would be £678 with the heat pump

 

Indeed, at £0.15/kWh. And the saving vs just the Willis would be twice that (£1356). So compared with a sensible heat pump price of around, say, £3000 (including a day for a plumber and a day for an electrician for the installation) you're talking about a break-even in just over two years which is also very reasonable. But it's not freezing all year and any use of cheap-rate electricity and/or PV will extend that significantly.

 

The RHI tax seems to be giving heat pumps a bad name, though. One neighbour was shaking his head about another neighbour's new £11'000 heat pump - “ordinary people can't afford that”. Will have a longer conversation with him at the next opportunity!

[Jeremy Harris]

I paid over the odds for our 7kW Glowworm (a re-badged Carrier 30AWH) ASHP, £1700, including delivery.  In terms of plumbing, then this is the biggest job, but still only took me around half a day, so allowing around £200 or so for it would seem reasonable.  Wiring was a lot quicker, just a multicore control cable plus a 2.5mm² power cable.  It didn't take as long as half a day, but being pessimistic then I could make the same £200 fitting cost allowance. 

 

That brings the installed cost to around £2100 (although my DIY installation reduced that a lot), but the same ASHP model (or very similar) can be bought now for around £1000 or less by shopping around, so even professionally installed I think that it should be quite reasonable to pay no more than £2000 at the very most for the installed cost for a unit of this sort of capacity.

[joe90]

4 minutes ago, JSHarris said:

I paid over the odds for our 7kW Glowworm (a re-badged Carrier 30AWH) ASHP, £1700, including delivery. 

 

I would have paid that back then as the payback period is reasonable but like all new things they come down in price (like P.V.). I was just willing to take a punt on an Ebay offering (I don’t  usually gamble but thought it was worth a go).

[ProDave]

37 minutes ago, Ed Davies said:

The RHI tax seems to be giving heat pumps a bad name, though. One neighbour was shaking his head about another neighbour's new £11'000 heat pump - “ordinary people can't afford that”. Will have a longer conversation with him at the next opportunity!

It seems any scheme or "initiative" to subsidise renewable energy just ends up with the subsidy paying a registered installer who has joined the "club" an over inflated price, while the consumer is no better off.

 

I have a very cynical view that it is just a scheme to benefit the installers, not the consumer.

 

The unbelievable bit is my friend that paid the £11K install is a plumber.

[TerryE]

@Gav_P, yes, at the moment we only use the Willis. We have prepared for adding an ASHP, but it will only be value for money if I self-fit a budget one.  As Jeremy says I am looking at a budget of around £2K, with a payback of ~3 years.  But that assumes that I will be doing my own maintenance, and not paying a third party. 

[Gav_P]

1 hour ago, TerryE said:

@Gav_P, yes, at the moment we only use the Willis. We have prepared for adding an ASHP, but it will only be value for money if I self-fit a budget one.  As Jeremy says I am looking at a budget of around £2K, with a payback of ~3 years.  But that assumes that I will be doing my own maintenance, and not paying a third party. 

I’m impressed. How many are you using? Just the one? 

 

I have gone the same same route as mention by JSH and Joe90 using the Carrier based ASHP (with complete self installation including all the UFH, rads and DHW). But due to a ballsup on my behalf, which ProDave has fixed, I installed the willis a couple of days ago and am quite surprised how well it works. 

 

However even with the cockups I reckon I’ve spent significantly less than £2k for the lot (that’s including my 300L Unvented hotwater cylinder which was my biggest expense).

 

If we have a winter like last year (which is forecast to be colder) then payback should be counted in months rather than years

[Jeremy Harris]

AFAIK, @TerryE just has one Willis heater, but bear in mind his house is built to the same standard as ours (same builder) so is pretty much to passive house standards, maybe better.  As such, the heating demand is pretty low - our house only needs 1600 W to maintain 21 deg C when it's -10deg C outside, and @TerryE's will probably be much the same.  As such, 3 kW from a Willis heater is more than enough.  Our 7 kW ASHP is a total overkill, and only ever runs at a very low power, and then only for an hour or two every couple of days.

[Gav_P]

1 minute ago, JSHarris said:

AFAIK, @TerryE just has one Willis heater, but bear in mind his house is built to the same standard as ours (same builder) so is pretty much to passive house standards, maybe better.  As such, the heating demand is pretty low - our house only needs 1600 W to maintain 21 deg C when it's -10deg C outside, and @TerryE's will probably be much the same.  As such, 3 kW from a Willis heater is more than enough.  Our 7 kW ASHP is a total overkill, and only ever runs at a very low power, and then only for an hour or two every couple of days.

1600w at -10! I haven’t even finished my current house, but I am feeling the draw of going down the passive house route and building from scratch next. 

[ProDave]

3 hours ago, Gav_P said:

1600w at -10! I haven’t even finished my current house, but I am feeling the draw of going down the passive house route and building from scratch next. 

Mine is not as good as @JSHarris and needs 2300W of heat input when it's -10 outside.  But still not bad.

[TerryE]

Also remember that with most passive houses - at least out MBC ones that use cellulosic filler - that the decrement delay is so long that spot lows are not really relevant; it is the daily average that's important. Last winter / spring was colder than average, and I don't think that we had a daily average below -5°C.  My house is larger than Jeremy's and a marginally lower spec, but even so based on actuals I am still at 1.85kW at this temperature, so only having one Willis isn't a real issue for us.

Edited November 3, 2018 by TerryE