With gas boilers potentially being banned in new homes from 2025, should we look at alternatives now

Martyn1981 · 13 October 2019 at 5:09PM

Holy methane burping cows Batman!

32,000kWh's of gas per year, how? And 1,000kWh's for DHW per month - I appreciate I don't smell like a rose, and there are only two of us, but our gas consumption for the last 6 months has been ~500kWh (46 units), and that includes the oven.

Anyways, back to the costs, remember that with a heat pump you'd be running it at night in your situation, so some of that leccy consumption would be cheap rate, and ideally, you might try to run it harder at night and lower during the day, when possible. Plus some PV, though for you that might be negligible.

Personally, I'm at the opposite end, as our heating was able to cope, but we have since improved insulation, and at every opportunity replaced rads with double plus ones, and longer if possible, so a heat pump would hopefully be viable, though we have to replace all the microbore with 15/22mm, but I ensured that access to all pipework and wiring would be easy(ish) when it was overhauled 20+yrs ago. For us, the hope would be to make greater use of cheap rate leccy, and some steep south faced PV panels would make a noticeable contribution during the day.

silverwhistle · 13 October 2019 at 5:44PM

That does seem a lot of gas. I wish I could calculate the kWh value of the wood I burn as my annual gas consumption is only 1000. Nothing in the last six months (all cooking by electric). Value of the scrounged wood is virtually nil: petrol for half a mile and my labour costs, which are cheap!

The economics on any capital investment for me, with a terrace house, are even more difficult to justify.

michaels · 13 October 2019 at 8:50PM

Solarchaser wrote: »

To get rid of the legionella issue, go for a 500l heat store instead, so the water is never stagnant, it just flows through the coil, the "dirty water" is heated instead, and transfers heat to the potable water through the coil.

That's what I'll be going for.

Interesting - I did a system like that before in our previous house although not nearly 500l.

Would this allow you to more efficiently use an inline direct electric heater to boost the temp above the store temperature which is optimised for heat pump?

michaels · 13 October 2019 at 9:09PM

Martyn1981 wrote: »

Holy methane burping cows Batman!

32,000kWh's of gas per year, how? And 1,000kWh's for DHW per month - I appreciate I don't smell like a rose, and there are only two of us, but our gas consumption for the last 6 months has been ~500kWh (46 units), and that includes the oven.

Anyways, back to the costs, remember that with a heat pump you'd be running it at night in your situation, so some of that leccy consumption would be cheap rate, and ideally, you might try to run it harder at night and lower during the day, when possible. Plus some PV, though for you that might be negligible.

Personally, I'm at the opposite end, as our heating was able to cope, but we have since improved insulation, and at every opportunity replaced rads with double plus ones, and longer if possible, so a heat pump would hopefully be viable, though we have to replace all the microbore with 15/22mm, but I ensured that access to all pipework and wiring would be easy(ish) when it was overhauled 20+yrs ago. For us, the hope would be to make greater use of cheap rate leccy, and some steep south faced PV panels would make a noticeable contribution during the day.

The maths says 1000 litres per day (10 showers and 2 baths) heated from 15 degrees to 45 degrees is 41kwh times 30 days is 1230 kwh per month.

Cardew · 13 October 2019 at 9:25PM

I don't know how many million families live in flats in UK, but for many of them Heat Pumps(all types) are impractical. Apart from the noise issue how do you mount and access the units on, say, a 20 storey block?

1961Nick · 13 October 2019 at 9:35PM

Martyn1981 wrote: »

Holy methane burping cows Batman!

32,000kWh's of gas per year, how? And 1,000kWh's for DHW per month - I appreciate I don't smell like a rose, and there are only two of us, but our gas consumption for the last 6 months has been ~500kWh (46 units), and that includes the oven.

5 showers & 1 bath per day suggests a household of 6 persons & therefore a reasonably large house?

If the above is true, then 32000 kWh doesn't seem unreasonable.

For comparison, 3 of us managed to consume 27910 kWh of gas last year & we're already up to 17000 this year - now with just 2 of us.

michaels · 13 October 2019 at 9:48PM

1961Nick wrote: »

5 showers & 1 bath per day suggests a household of 6 persons & therefore a reasonably large house?

If the above is true, then 32000 kWh doesn't seem unreasonable.

For comparison, 3 of us managed to consume 27910 kWh of gas last year & we're already up to 17000 this year - now with just 2 of us.

That is correct, although the showers and bath are all twice a day but obviously there is min 7 or 8 hours of cylinder warm up time between each set of 6.

House is about 170sqm 5 bed semi half built in 1938, the other half in 2010, allegedly EPC B - heating is 24/7 set at 17 degrees at night and 21 in the day but probably generally a bit warmer as this is by weather cop not interior thermostat and monitoring suggests that the coolest room meets the 17/21 threshold.

1961Nick · 13 October 2019 at 9:54PM

michaels wrote: »

Interesting - I did a system like that before in our previous house although not nearly 500l.

Would this allow you to more efficiently use an inline direct electric heater to boost the temp above the store temperature which is optimised for heat pump?

An electric water heater fitted after the heat store would boost the hot water temperature. Something like a 10 kWh heater would do the job.

Here's a random one...

https://www.screwfix.com/p/strom-seih11kts1-touchscreen-instantaneous-water-heater-11kw/4681p

michaels · 13 October 2019 at 9:59PM

1961Nick wrote: »

An electric water heater fitted after the heat store would boost the hot water temperature. Something like a 10 kWh heater would do the job.

Here's a random one...

https://www.screwfix.com/p/strom-seih11kts1-touchscreen-instantaneous-water-heater-11kw/4681p

Thanks - cop on that is 1 of course and no time shifting to cheaper leccy periods possible.

What sort of temp can a heat pump heat hot water too before it becomes disastrously inefficient? Does it differ for an ashp that has to contend with very low temps vs a horizontal or even vertical loop gshp?

mmmmikey · 13 October 2019 at 10:29PM

A thought going through my mind here is that given the high usage you may find it's more efficient and cost effective to separate water heating from central heating. Possibly solar hot water panels heating a suitably sized thermal store using immersion heaters on E7 for boost?

With gas boilers potentially being banned in new homes from 2025, should we look at alternatives now

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