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How hard and expensive would it be to change panel and add battery?

Air Source Heat Pumps (ASHPs)

Last Post by Judith 9 hours ago

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Ellyse

(@ellyse)

Trusted Member Member

208 kWhs

Joined: 7 months ago

Posts: 29

Topic starter 12/04/2025 8:44 am

We were lucky to get gov-funded installation of Mitsubishi heat pump, Ecodan control, radiators, water tanks, extra insulation extraction fans and solar panels. Completely free to us. Snag was no control, no options, our mini-estate got a standard set up across all. The electric panel does not support battery storage.

So I am just wondering what kind of area of cost to replace that board with one that does support battery storage, and add battery as needed. Also how difficult is it likely to be to find someone willing to do the work within 12 months of the original install? Thanks

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bontwoody

(@bontwoody)

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5499 kWhs

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Posts: 798

12/04/2025 9:02 am

Hi. You would probably need to swap the inverter for a hybrid inverter. That would support battery charging. However I would look into the cost v payback time as many have come to the conclusion that it just doesn’t make financial sense at the moment.

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60

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Judith

(@judith)

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12/04/2025 9:21 am

If you have a decent export tariff such as Octopus’s 15p then you use the export to build up your cash in your account over the summer and then spend it in winter.
Broad brush guess on price for a reasonable sized battery and its inverter is a few thousand, you may also need some panels re-wired (less likely) which would be scaffolding which is about £1k.

The best size of battery is to cover your use for an average day or the size to last about 6hours on your worst case use rate. There’s a lots more to be said on this but that’s my rough conclusion after playing with excel on our usage for ages.

In doing a payback your potential battery would only last for the same day. We at present are generating 30kWh each day, the heat pump (and the house) use 16-20kWh so there’s lots to export. Think of it as a seasonal sized battery!

Octopus would give you an on line estimate for a battery and then their sales team will pester you and you’ll get the timing. But the payback time maybe above 15years.

This post was modified 16 hours ago 2 times by Judith

2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with it) open system operating on WC

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bontwoody

(@bontwoody)

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5499 kWhs

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12/04/2025 9:46 am

@judith that’s interesting as my calculations suggested a smaller battery that didn’t last the day was more cost effective for me. I couldn’t even make the case for an extra module given I already had the inverter and battery management system.

As you say a 15 year payback time seems about right but will the battery last that long? Mine has a 10 year warranty.

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Ellyse

(@ellyse)

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Topic starter 12/04/2025 9:49 am

15 years? crikey! I'm age 65 so that will definatley not be worth it. Thanks for the info. 🙂

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Ellyse

(@ellyse)

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208 kWhs

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Posts: 29

Topic starter 12/04/2025 9:49 am

wouldn't post despite clicking over and over, then posted multiple. Sorry. Isn't letting me delete the extras. Feel free to tidy my mess lol

This post was modified 15 hours ago by Ellyse

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Ellyse

(@ellyse)

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208 kWhs

Joined: 7 months ago

Posts: 29

Topic starter 12/04/2025 9:49 am

... 🙂

This post was modified 15 hours ago by Ellyse

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Ellyse

(@ellyse)

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208 kWhs

Joined: 7 months ago

Posts: 29

Topic starter 12/04/2025 9:50 am

.... 🙂

This post was modified 15 hours ago by Ellyse

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Judith

(@judith)

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12/04/2025 4:33 pm

Posted by: @ellyse

↑

15 years? crikey! I'm age 65 so that will definatley not be worth it. Thanks for the info. 🙂

That’s just a guess, and your usage patterns may vary. It might be worth trying to work it out for your circumstances.

If you want to improve your comfort (and possibly your bills) then better control might be the best route forward. I don’t know personally where to start with an Ecodan.

2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with it) open system operating on WC

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