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ASHP in Hampshire

batalto · 2021-04-22T13:28:11Z

Hi all, Just wanted to talk you through our upcoming ASHP installation. We live on the south coast, just outside of Portsmouth. The house is a detached home of around 260m2 in footprint. The bottom floor was an extended bungalow and we added a second floor. The first floor is standard construction, brick cavity that's filled and double glazed. The upper floor is made of Structurally Insulated Panels (SIPs) with triple glazing. We had to use SIPs because they are lightweight and so wouldn't affect the shallow bungalow foundations. As an upside SIPS are also extremely efficient in retaining heat and have a very low U value, 0.18. The loft has 200mm of insulation in the middle beneath the floor and 400mm of insulation for everywhere else. We have 8.4kW of solar PV on the roof and 7kWh of battery storage (Pylontech batteries). We also have a Solic solar PV heat controller, which will dump excess solar power into the tank before we export. We've just had our EPC done and we scored very highly A (93) that also provided a heat demand of 34w/m2 which tallies with our ASHP assessment of 36w/m2. The ASHP is a 12kw Midea with a stated SCOP of 3.36 supplied and installed by J A Rees, sourced from Freedom Heat Pumps - total cost just under £10k. We will be replacing our current 32kW gas system boiler and hot water cylinder and using the green homes grant for £5k of the cost and I will paying the other £5k. We qualify for the highest RHI so would expect to get roughly £7200 back over the next 7 years. The boiler will be retained as a backup heating system and isolated from the ASHP system. We have been told this is fine with the RHI as its a backup and not hybrid. The heating is currently set to 45 degrees and we have had no problems. Our main living area has a large bifold door system and west facing. This means we have significant heat loss in the winter and for 2 months its very cold and this makes the room chilly, but not cold. All the other months the solar gain is significant, heating the room and the rest of the house. With the conventional boiler the room is chilly, so I am expecting issues in January heating up the room. We might need to come up with a plan for this room, possibly some thick curtains. The install will be next week and should be very straightforward. The ASHP will go on the drive next to the current power intake. The pipework will go straight through the wall into the current boiler room and tap into the current pipework. The tank will need replacement for one with a larger coil, but more or less everything else will remain the same. The aim is 2 days. Currently our gas is 2.5p and electricity is 14p and the current boiler is 58% efficient (according to the boiler) - this leads to a bill of around £1250 for both gas and electricity for the year. With the ASHP, boiler efficiency and assuming a worse SCOP of 2.7 on the current tariff we expect the bill to fall to just under £1,000 (34,000kw of gas to 7,000kw of electricity). This cost includes a standing charge for gas even though we wont be using it. My plan after we have got used to the ASHP is to upgrade the batteries and add 7kw extra, then move to a new tariff. Agile GO is very interesting as I could fill my batteries at night and expend them during the day. The batteries would store 11.4kw (14kW @ 80% Depth of Discharge). I have estimated this would further drop my bills down to £780

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Air Source Heat Pumps (ASHPs)

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batalto

(@batalto)

Noble Member Member

Joined: 6 years ago

Posts: 1092

Topic starter 01/03/2022 10:23 am

Update for the month (Feb)

ASHP use: 909kW

Total use: 1305kW

Power purchased: 1060kW

Last Bill - Jan 20th to Feb 20th - £172 @ effective price of 10.68p/kw + standing charges

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE

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batalto

(@batalto)

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Joined: 6 years ago

Posts: 1092

Topic starter 22/03/2022 11:30 am

latest update on electricity bills - my latest bill (Feb 20 - Mar 20) is roughly half the previous bill

This is for ALL power including domestic and ASHP. As you can see over half was "off peak" rates (so 00:30 - 04:30) and went to night time ASHP and battery charging

Example day from the 19th of March - a nice sunny day. You can see basically zero power use outside of the "off peak" hours. I expect moving forward my bills will begin to drop towards zero, with only standing charges remaining. My battery is set to stop filling in April, however I might extend this to maybe 50% fill for April, as I wind down my grid use entirely.

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Kev M

(@kev-m)

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Posts: 1276

22/03/2022 3:54 pm

@batalto

If you were like me and had no pv/batteries, how many kWh do you think you would have used and how much would it have cost you at cap rates?

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batalto

(@batalto)

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Posts: 1092

Topic starter 22/03/2022 4:47 pm

@kev-m whatever you think you need - double it.

As I said on a previous post I think you can build it fairly cheaply, it depends how much you want? Do you know your use?

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Kev M

(@kev-m)

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Joined: 6 years ago

Posts: 1276

22/03/2022 4:52 pm

I'm thinking about it seriously now. I'm not sure what the numbers would look like without the tariff you have; I don't think it's available.

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Derek M

(@derek-m)

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Posts: 4425

22/03/2022 5:17 pm

Posted by: @kev-m

I'm thinking about it seriously now. I'm not sure what the numbers would look like without the tariff you have; I don't think it's available.

Hi Kev,

I think that you are correct, that the tariff that Batalto is currently enjoying will never be available again, since the Go Tariff will increase in April to approximately 7.5p/kWh during the 4 hour cheap period, and I can't remember if the expensive rate was in the 20 or 30 pence range.

I was moved to Octopus last September onto their variable tariff, and I have just looked (as a customer) to see what the Go Tariff is now, and if it was possible to change tariff. I was only offered one ridiculously expensive tariff, which certainly wasn't Go.

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batalto

(@batalto)

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Joined: 6 years ago

Posts: 1092

Topic starter 22/03/2022 5:34 pm

@kev-m ours was worth it, even without Go. Go was just another benefit for us

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batalto

(@batalto)

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Joined: 6 years ago

Posts: 1092

Topic starter 22/03/2022 7:07 pm

@kev-m @derek-m go is at this link. Have a go and see how you get on?

https://octopus.energy/go/

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Kev M

(@kev-m)

Noble Member Member

Joined: 6 years ago

Posts: 1276

22/03/2022 7:35 pm

But I don;t have a smart meter ...

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Derek M

(@derek-m)

Illustrious Member Member

Joined: 6 years ago

Posts: 4425

22/03/2022 7:37 pm

Posted by: @batalto

@kev-m @derek-m go is at this link. Have a go and see how you get on?

https://octopus.energy/go/

Hi Batalto,

Whilst the site provides the tariff rates 7.5p and 29.82p, it would appear that it will not allow one to switch to that tariff.

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batalto

(@batalto)

Noble Member Member

Joined: 6 years ago

Posts: 1092

Topic starter 22/03/2022 7:44 pm

@kev-m I didn't have one. I just signed up and had to wait for it to be installed. Took ages though

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batalto

(@batalto)

Noble Member Member

Joined: 6 years ago

Posts: 1092

Topic starter 22/04/2022 8:44 am

Monthly bill update from me - £61 (698kw) for the last month, all heating and power purchased for everyday use. Actual use as 1185kw (roughly)

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