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Using Annual Gas Consumption to understand what an ASHP may consume in electricity

 
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Air Source Heat Pumps (ASHPs)
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 Nick.T
(@nick-t)
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Joined: 4 years ago
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Topic starter 02/11/2021 3:21 pm  

I have a 1920s 4 bed detached house in Surrey and I am thinking of changing to an ASHP.  My gas bills show that I use 29,000 kwh per annum of gas  - is there an easy way to understand what might be achievable in terms of electricity use from an air source heat pump to achieve the same level of heating? or are there too many other variables?



   
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 George
(@george)
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Posts: 85
02/11/2021 3:39 pm  

Hi Nick,

Its more important to understand the current setup of your property in regards to insulation, double/triple glazing, radiators/underfloor heating/pipework etc.

There are a couple of review/threads on the forum where people post their data but every property/installation is different so its hard to compare to your property. 

 

What is pushing you towards looking at an ASHP?


Mitsubishi Ecodan 14kw ASHP + 500l Cylinder


   
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 Brendon Uys
(@heacol)
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Posts: 415
02/11/2021 3:52 pm  
Posted by: @nick-t

I have a 1920s 4 bed detached house in Surrey and I am thinking of changing to an ASHP.  My gas bills show that I use 29,000 kwh per annum of gas  - is there an easy way to understand what might be achievable in terms of electricity use from an air source heat pump to achieve the same level of heating? or are there too many other variables?

If the system is designed and operated properly, you should cut about 20-30% off that.

 



   
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 Nick.T
(@nick-t)
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Joined: 4 years ago
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Topic starter 02/11/2021 4:01 pm  

@george .  I want to dispense with my gas connection altogether in order to reduce carbon emissions.  I understand that the Domestic RHI is ending in March 2022 and the replacement scheme would seem to be a reduction in the value of the incentive for a property my size (flat 5k vs about 10k spread over 7 years).



   
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 Derek M
(@derek-m)
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Posts: 4425
02/11/2021 4:10 pm  
Posted by: @nick-t

I have a 1920s 4 bed detached house in Surrey and I am thinking of changing to an ASHP.  My gas bills show that I use 29,000 kwh per annum of gas  - is there an easy way to understand what might be achievable in terms of electricity use from an air source heat pump to achieve the same level of heating? or are there too many other variables?

Hi Nick,

Welcome to the forum.

As a very rough, ballpark figure, you could probably expect electrical energy consumption to be 1/4 that of your gas consumption, if you were to fit a well designed, installed and optimised ASHP system.

If your objective is to save the planet and don't mind the additional cost, based on present gas and electricity tariffs, then you are to be commended. If your desire is to help save the planet and also improve your bank balance they it may be best to look at improving the level of insulation first. 



   
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Jeff
 Jeff
(@jeff)
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02/11/2021 4:27 pm  

Have I miss understood

@heacol says 20% to 30% off the gas consumption figure? 

@derek-m says 75% off the gas consumption figure? 



   
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 Brendon Uys
(@heacol)
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02/11/2021 4:32 pm  

@jeff Same thing



   
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 Derek M
(@derek-m)
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Posts: 4425
02/11/2021 5:58 pm  
Posted by: @jeff

Have I miss understood

@heacol says 20% to 30% off the gas consumption figure? 

@derek-m says 75% off the gas consumption figure? 

Hi Jeff,

I think it may be a freudian slip. I do believe Brendon's statement should read ' 20% to 30% of the gas consumption figure', which of course would be approximately the same.

Dependent upon the heat loss of the property, along with the type and size of the heat emitters, a conservative estimate would be a SCOP of 4 for a well designed, installed and optimised system. Without specifics it is impossible to be any more accurate.



   
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 Brendon Uys
(@heacol)
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Joined: 5 years ago
Posts: 415
02/11/2021 6:02 pm  

@derek-m 😆 👍 



   
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 Nick.T
(@nick-t)
Active Member Member
Joined: 4 years ago
Posts: 4
Topic starter 03/11/2021 8:01 am  

@derek-m 

I have already installed cavity wall and loft insulation - and will install floor insulation and underfloor heating on the ground floor in some renovations next year.



   
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 Nick.T
(@nick-t)
Active Member Member
Joined: 4 years ago
Posts: 4
Topic starter 03/11/2021 8:07 am  

@derek-m 

Thanks - this now makes sense and would bring the cost of electricity to roughly the same ballpark as gas.  

I have a few questions on how best to optimise but I will start another thread on that. 



   
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 MarkC
(@markc)
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Joined: 4 years ago
Posts: 97
03/11/2021 8:55 am  

As a rough comparison I had 3 quotes in Nov 2020 for:

14Kw Mitsubishi Ecodan pump

250l DHW tank

6 new radiators

MMSP

One came in at £14K and the others (which may have been £1K extra) were willing to match. They all charged £1K for MMSP which was included in the £14K.

 

Regarding MMSP. although it may sound like it's for geeks I would highly recommend having it installed, especially if you intend registering for RHI as you get it for free effectively.

I'm just going through fine tuning my ASHP on another forum topic  and MMSP has been invaluable in identifying how the system is performing and whether action needs to be taken.

It will also allow the installers to remotely access your system if an error can be resolved without an engineer visit.

 



   
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