Discussion ... ASHP(Air/Air) with Solar pv ....

zeupater

ASavvyBuyer wrote: »

... So by using 11.3 kWh extra of imported electric we have saved the equivalent of nearly 26 times the amount of gas...

Hi

The reduction in gas usage looks to be far too high to just be related to the heat-pump considering what would be available from the pv system at this time of year, particularly considering the conditions over the past week ... could it be the case that with the 'living area' heating being assisted by the heat-pump the main GCH thermostat is cutting out earlier or there's been additional insulation fitted ?

Based on a quick guesswork exercise which assumes that both weather and general consumption was roughly the same as last year .... if generation over the past week was ~30kWh and (maybe) ~10kWh of that plus the additional 11.3kWh mentioned was consumed by the heat-pump, that gives us around 21/22kWh of electricity used which when adding a COP multiplier (5.5-6.0) would likely provide around 115 to 130kWh.t (ish) over the week ... however, as mentioned above, there's nothing to say that this additional heat provided in the 'right place' hasn't allowed the rest of the house to cool a little (possibly almost unnoticeable ??) saving the additional ~170kWh.

Anyway, good to see you're happy so far ... our stack of logs currently seems to be much healthier than normal as we approach December and our electricity usage seems to be almost spot-on with last year, which is all I can go on at the moment .... and, of course, the house definitely 'feels' warmer where it matters (I don't have historical temperature data by room!)..

HTH
Z

ASavvyBuyer

zeupater wrote: »

Hi

The reduction in gas usage looks to be far too high to just be related to the heat-pump considering what would be available from the pv system at this time of year, particularly considering the conditions over the past week ... could it be the case that with the 'living area' heating being assisted by the heat-pump the main GCH thermostat is cutting out earlier or there's been additional insulation fitted ?

Based on a quick guesswork exercise which assumes that both weather and general consumption was roughly the same as last year .... if generation over the past week was ~30kWh and (maybe) ~10kWh of that plus the additional 11.3kWh mentioned was consumed by the heat-pump, that gives us around 21/22kWh of electricity used which when adding a COP multiplier (5.5-6.0) would likely provide around 115 to 130kWh.t (ish) over the week ... however, as mentioned above, there's nothing to say that this additional heat provided in the 'right place' hasn't allowed the rest of the house to cool a little (possibly almost unnoticeable ??) saving the additional ~170kWh.

Anyway, good to see you're happy so far ... our stack of logs currently seems to be much healthier than normal as we approach December and our electricity usage seems to be almost spot-on with last year, which is all I can go on at the moment .... and, of course, the house definitely 'feels' warmer where it matters (I don't have historical temperature data by room!)..

HTH
Z

Hi Z
What you are suggesting is probably the case for the bulk of the fall in gas use. We have a "heatmiser" wireless programmable thermostat that I bought of ebay for £25 a few years go. Instead of that being in the lounge now, it is now placed either in the bedroom or kitchen to control the central heating from there. The Toshiba Unit thermostat now controlling the temperature in the lounge, with the radiator thermostatic valve in there on a very low setting.
We have found that we only need the GCH on now for an hour in the morning & at night for those rooms now, except when we boost it for 30 minutes or more if needed for longer..
Also, the kitchen has a bit more insulation above it in the loft, after fitting a new insulated loft hatch/ladder earlier this year.
I too was supprised at the drop in gas use, but very pleased to see it. :j
Our home also "feels" warmer, where it matters; and we are tending to spend more time in the lounge admiring our view of the Brecon Beacons

Martyn1981

zeupater wrote: »

... however, as mentioned above, there's nothing to say that this additional heat provided in the 'right place' hasn't allowed the rest of the house to cool a little (possibly almost unnoticeable ??) saving the additional ~170kWh.

HTH
Z

Cheers guys, this is really helpful and interesting.

Z, you may be right, I was surprised yesterday as I had the 400W oil rad on most of the day, the living room was pleasant, but when I popped upstairs it was about 17C and quite nippy. I hadn't realised this had been happening, nor how well things were working.

Still jealous of you boys, but cunning plan R or is it S now, still being pondered.

ASavvyBuyer

ASavvyBuyer wrote: »

Hi Z
What you are suggesting is probably the case for the bulk of the fall in gas use. We have a "heatmiser" wireless programmable thermostat that I bought of ebay for £25 a few years go. Instead of that being in the lounge now, it is now placed either in the bedroom or kitchen to control the central heating from there. The Toshiba Unit thermostat now controlling the temperature in the lounge, with the radiator thermostatic valve in there on a very low setting.
We have found that we only need the GCH on now for an hour in the morning & at night for those rooms now, except when we boost it for 30 minutes or more if needed for longer..
Also, the kitchen has a bit more insulation above it in the loft, after fitting a new insulated loft hatch/ladder earlier this year.
I too was supprised at the drop in gas use, but very pleased to see it. :j
Our home also "feels" warmer, where it matters; and we are tending to spend more time in the lounge admiring our view of the Brecon Beacons

Thought of another reason for the drop in gas use. As the lounge is pre-heating during the day using the Toshiba Unit, we have not needed to have the gas fire on to quickly raise the temperature when the GCH has been off during the day, as the room is already warm. As the gas fire is only 50% efficient, at best, that could help account for the larger than expected fall.

Martyn1981

ASavvyBuyer wrote: »

As the gas fire is only 50% efficient, at best, that could help account for the larger than expected fall.

When we bought our house it had 3 storage heaters (next to useless) and a gas fire in the living room. After a year of saving we had GCH installed, we went from a cold house to a warm house with no change to gas consumption, and a big drop in leccy consumption.

Hope I'm not cheating on the maths, but it seems logical to me that the GCH for the whole house was equal to the consumption just from the one fire, in fact better, as it also replaced the 3 storage heaters. [Edit - DHW would have been electric, so that too was moved onto gas with the install of the combi boiler. M.]

zeupater

Hi

For info ... as posted elsewhere ...

zeupater wrote: »

Hi All

Mixed month which was only saved by the last week ending up as the 3rd best total for November and around 40kWh higher than last year ....

Gas consumption was 35kWh and electricity imports were 117kWh, around 600Wh down on last year so the heat-pump has made little difference to the bill and a considerable difference to both comfort levels and the remaining size of the log pile ....

HTH
Z

... so not bad and just about where I hoped it would be (around the same!) when considering the displacement of occasional use of direct resistance heating in previous years ....

HTH
Z

ASavvyBuyer

Just over a month now since the Toshiba Air Conditioner/Heat Pump was installed.

Comparing Gas & Electric use from the same period last year have ended up with the following figures:

Gas use down by 581.76 kWh
Electric import up by 44.12 kWh

December being our worst month for PV generation, as the sun does not rise above the mountain.

Comfort level increased too, as lounge feels warmer most of the day with the steady flow of heat from the heat pump.

Outside unit very quiet; sometimes when outside have to go and check that it is actualy running as I can't hear it from more than a few yards away!

Looking forward to the early Spring, when most, if not all of the power for it comes from the solar panels.

rugbyleaguesmate

Hi there just had an email through about FIT rates changing for heat pumps, can someone advise how this works please? And am I right in thinking you would have a heat pump or a battery? You wouldn't be able to have both?

zeupater

rugbyleaguesmate wrote: »

Hi there just had an email through about FIT rates changing for heat pumps, can someone advise how this works please? And am I right in thinking you would have a heat pump or a battery? You wouldn't be able to have both?

Hi

There's been some 'minor' changes to the RHI scheme and relevant tariffs - ( Ofgem details : https://www.ofgem.gov.uk/environmental-programmes/domestic-rhi/contacts-guidance-and-resources/tariffs-and-payments-domestic-rhi/current-future-tariffs )

Note that RHI covers ASHP (Air/Water) and GSHP not Air/Air (unfortunately) ... relevant changes are linked to system underperformance mainly due to poor installation design & operation setup - just goes to show that DECC had absolutely no idea what they were talking about (as usual) when designing the scheme !!

HTH
Z

ASavvyBuyer

First full month (December) since the Toshiba Air Conditioner/Heat Pump was installed.

Comparing Gas & Electric use from December last year have ended up with the following figures:

Gas use down by 338 kWh
Electric import up by 73 kWh

Weather been slightly colder, with more cold snaps, compared to last December.