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Peering over the ASHP cliff

 
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Air Source Heat Pumps (ASHPs)
Last Post by Oswiu 3 years ago
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 Oswiu
(@oswiu)
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Joined: 3 years ago
Posts: 121
19/12/2022 8:36 am  

@grahamb that all seems quite reasonable then for the 9kW quote. My pipe run for my monobloc is about 10m there, 10m back. The manual does allow longer pipe runs with careful design, but generally if you're having a long pipe run you'll want a split system which is when the refrigerant is pumped inside and heats water once inside the house in a box on the wall. They require a bit more space inside, but less outside, and they also need to be installed by an F Gas safe engineer so I think they're getting less popular.

I got hit with additional fees of about £1k for long cable and pipe runs. I suggest if they haven't taken that into account and they want to add a cost on that you think about hiring a third party electrician.

That 19,309kWh will be delivered heat, not electricity, so that's the part that would end up being roughly the same as your gas bill. I wouldn't worry if it's much higher or lower, just assume it'll be similar. They'll have probably estimated electricity usage to be between 5,000 and 6,000kWh for the heat pump.

 


   
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 GrahamB
(@grahamb)
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Topic starter 19/12/2022 9:21 am  

Posted by: @oswiu
↑

That 19,309kWh will be delivered heat, not electricity, so that's the part that would end up being roughly the same as your gas bill. I wouldn't worry if it's much higher or lower, just assume it'll be similar. They'll have probably estimated electricity usage to be between 5,000 and 6,000kWh for the heat pump.

 

Wow! Using your lower figure, that's going to ADD around £400 to my energy bill, using the higher number, that's £853 and that's totally ignoring the gas cooker.

 


   
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 Oswiu
(@oswiu)
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Joined: 3 years ago
Posts: 121
19/12/2022 9:27 am  

@grahamb yes but you use less gas than that. Take your gas usage in kWh and divide it by 3 or 4 to get your heat pump usage. I think a gas hob normally accounts for only about 1 or 2% of your gas usage so you can basically ignore it


   
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 GrahamB
(@grahamb)
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Joined: 3 years ago
Posts: 10
Topic starter 19/12/2022 9:47 am  

@oswiu I'm a little confused now. Earlier you indicated my electricity usage would be around 5-6,000kWh for my heat pump. I used those numbers?


   
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 Oswiu
(@oswiu)
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Joined: 3 years ago
Posts: 121
19/12/2022 10:06 am  

@grahamb I was saying they may have estimated that from guessing your heating/hot water needs at 19000kWh. If your needs are lower than that, which it seems like they are, then you won't use that much.

They may have given you an estimated 'efficiency' across the year called SCOP or COP or SPF which you can divide your actual gas usage by to get estimate electricity usage. It'll probably be between 3 and 4. The lower the flow temp is (and the bigger your radiators), the bigger this number will be.

When you say they included an 18L vessel in your quote, you should ask them if that's an in-line volumiser or buffer. If it's a buffer you should ask why you need it since they can sometimes be useful but also lower efficiency. 


   
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