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High air source heat pump running costs – Vaillant AroTherm Plus

 
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Air Source Heat Pumps (ASHPs)
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Batpred
 Batpred
(@batpred)
Prominent Member Member
Joined: 1 year ago
Posts: 801
23/04/2026 12:23 am  

Posted by: @majordennisbloodnok
↑

If I were to install 18 panels today, I'd get more efficient ones and 550W JA units are approximately £94 each. Pro-rating the generation, I'd expect approximately 382kWh from each of them over a year. If we use your model of importing cheap to fill up the battery and then using that for home and heat pump, that effectively means each of those 382kWh from a panel is worth 12p to me since that's my current export rate (and yes, I realise that could change, but so as I said could the import rate in your model), which works out at just under £46. That's a paypack of just a smidge over two years. Even taking into account the installation costs on top of that, we're still looking at a pretty reasonable break even point.

Ahem.. 🙂 

A PV panel may be £94, so £750k for 4kwp, but the labour and other bits involved in getting PV installed changes the whole equation. Of course we all know that £4k for 4kwp installed would be excellent value including MCs etc..

And should we have plug in solar for £94 a panel (will we?), we would be on another league.

In any case, I still see payback vs that 3.5 p/kwh overnight rate, which I cannot see being beaten. Of course that can change and make the dream payback more aligned with normal investment.. 😉 

 


This post was modified 2 days ago 2 times by Batpred

8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kw export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; 100Amp head, HA lab on mini PC


   
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Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
Famed Member Moderator
Joined: 4 years ago
Posts: 1759
23/04/2026 8:54 am  

Posted by: @marcexec
↑

Posted by: @bash
↑

@majordennisbloodnok 

I saw that 64kwh battery for £6000 and I wanted one immediately, even though I already have 45kwh of Fogstar batteries 😆

If you have a good (outdoor) location, a good few people re-use EV batteries with 400V capable inverters: 

@marcexec, that's a very interesting project. Thanks for that.

 


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
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Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
Famed Member Moderator
Joined: 4 years ago
Posts: 1759
23/04/2026 9:16 am  

Posted by: @batpred
↑

Posted by: @majordennisbloodnok
↑

If I were to install 18 panels today, I'd get more efficient ones and 550W JA units are approximately £94 each. Pro-rating the generation, I'd expect approximately 382kWh from each of them over a year. If we use your model of importing cheap to fill up the battery and then using that for home and heat pump, that effectively means each of those 382kWh from a panel is worth 12p to me since that's my current export rate (and yes, I realise that could change, but so as I said could the import rate in your model), which works out at just under £46. That's a paypack of just a smidge over two years. Even taking into account the installation costs on top of that, we're still looking at a pretty reasonable break even point.

Ahem.. 🙂 

A PV panel may be £94, so £750k for 4kwp, but the labour and other bits involved in getting PV installed changes the whole equation. Of course we all know that £4k for 4kwp installed would be excellent value including MCs etc..

And should we have plug in solar for £94 a panel (will we?), we would be on another league.

...

Quite right. I was using a rough guesstimate of doubling the panel costs to get to a true installation cost, meaning a break even point of about 4 years which I would still expect most people to be comfortable with as an investment.

Posted by: @batpred
↑

...

In any case, I still see payback vs that 3.5 p/kwh overnight rate, which I cannot see being beaten. Of course that can change and make the dream payback more aligned with normal investment.. 😉 

And that, of course, is where the different viewpoints converge.

My total solar PV generation last year would, if taken instead from grid, have cost £162. I can't ignore the logic I put forward earlier but I also can't ignore your point of comparing break even with 3.5p/kWh. Nor do I think I should be discounting any of these points; the reality is that there are so many different ways of slicing and dicing this that the only practical way forward is, as @bash said, to do the numbers in one's own context and see what adds up best.

I will also happily admit I'm no accountant. Faced with two new figures that are better than my current situation, I see either a win or a big win. I can't bring myself to frame a sub-optimal gain as a form of loss because of the theoretical bigger gain I could've achieved. No doubt that colours my viewpoint in this whole discussion.

 


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
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