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This does not make sense - documents needed for EPC score

 
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Solar Photovoltaic (PV)
Last Post by Derek M 3 years ago
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 Tim441
(@tim441)
Honorable Member Contributor
Joined: 4 years ago
Posts: 414
23/02/2023 11:27 am  

@derek-m the problem with that is trying to get it assessed in a consistent way? Taking into account numbers, ages of occupants? at home all day? impact of solar gain? some people heat whole house ... others heat one room only to say 20 or 21... etc etc

i've no idea if its possible to have a way of measuring heat loss in some way to get useful info. But again i'm sure there are many issues with trying to do that so it can be measured in all weathers & times of year!

 


Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8.7kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV


   
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 Mike Patrick
(@mike-patrick)
Reputable Member Member
Joined: 5 years ago
Posts: 196
23/02/2023 8:44 pm  

Posted by: @mike-patrick
↑

@derek-m I like that idea as it's one number that everyone can understand. Hides a lot behind it but a useful heuristic.

Last year for mine (total energy use as ASHP not separately metered) was £70 per year per sq.m. Without others to compare I've no idea whether this is good, bad or typical. The only comparison I know of is my aged relative's house (80's built and well insulated). She uses almost 3x my annual kWh (28,000 KWh of gas and electricity). She can afford it but I've told her to use the coal-effect gas fire less and get a new thermostat for the hall as the existing one seems not to work.

Mike

I meant 70 kWh p.a. per sq.m, not £70

 


Grant Aerona HPID10 10kWh ASHP


   
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 Andris
(@andris)
Estimable Member Member
Joined: 5 years ago
Posts: 128
Topic starter 23/02/2023 8:48 pm  

For comperson I used 10000kw 5 people 230m². But it is a newbuild.


16kw Samsung TDM ASHP. 8.4kw PV, power optimizers 20×420watt panels 6kw SolarEdge inverter.


   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4425
23/02/2023 9:07 pm  

Posted by: @mike-patrick
↑

Posted by: @mike-patrick
↑

@derek-m I like that idea as it's one number that everyone can understand. Hides a lot behind it but a useful heuristic.

Last year for mine (total energy use as ASHP not separately metered) was £70 per year per sq.m. Without others to compare I've no idea whether this is good, bad or typical. The only comparison I know of is my aged relative's house (80's built and well insulated). She uses almost 3x my annual kWh (28,000 KWh of gas and electricity). She can afford it but I've told her to use the coal-effect gas fire less and get a new thermostat for the hall as the existing one seems not to work.

Mike

I meant 70 kWh p.a. per sq.m, not £70

 

I was thinking more on a daily or even hourly basis, since that may be more effective when adjusting the weather compensation curve.

One possible way to get a feel for actual heat loss, would be to warm your home to 21C, note the outside temperature and time, then switch off your heating system and time how long it takes for the indoor temperature to fall to 20C, noting the final outside temperature. 

By doing the above at several different outside temperatures it may provide the sloop of the heat loss.

It may then be possible to check the results against the calculated heat loss for your home.

 



   
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 batalto
(@batalto)
Noble Member Member
Joined: 5 years ago
Posts: 1092
23/02/2023 9:11 pm  

@andris I used 7,000kw last year. Slightly bigger house 263m2, 4 people (2 young children).

So that's 26.6kw/m2 per annum

 


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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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4425
23/02/2023 9:15 pm  

Posted by: @batalto
↑

@andris I used 7,000kw last year. Slightly bigger house 263m2, 4 people (2 young children).

So that's 26.6kw/m2 per annum

 

Did you include your solar generation in those figures?

 



   
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 Andris
(@andris)
Estimable Member Member
Joined: 5 years ago
Posts: 128
Topic starter 23/02/2023 9:19 pm  

@derek-m funny I was thinking the same.


16kw Samsung TDM ASHP. 8.4kw PV, power optimizers 20×420watt panels 6kw SolarEdge inverter.


   
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 batalto
(@batalto)
Noble Member Member
Joined: 5 years ago
Posts: 1092
23/02/2023 9:22 pm  

@derek-m no, that's actual heat pump use regardless of source.

Screenshot 2023 02 23 20 24 03 54 f90b96e7af3c5a594eb0c92de7fc5fe1

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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 Andris
(@andris)
Estimable Member Member
Joined: 5 years ago
Posts: 128
Topic starter 23/02/2023 9:31 pm  

@batalto I see, my total of heating use is a bit of a guess as I don't have a meter. I use 10000kw total usage. Heating about 3500kw. Hot water 2500kw and 4000kw is washing drying all other electrical items.


16kw Samsung TDM ASHP. 8.4kw PV, power optimizers 20×420watt panels 6kw SolarEdge inverter.


   
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 batalto
(@batalto)
Noble Member Member
Joined: 5 years ago
Posts: 1092
23/02/2023 9:35 pm  

I used about 6,500kw for power in the house. However a good chunk of that is my abusing the solar in the summer running AC, a pool heater and a hot tub. So not really representative lol


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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1
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 Andris
(@andris)
Estimable Member Member
Joined: 5 years ago
Posts: 128
Topic starter 23/02/2023 9:39 pm  

😀  that's awesome!. Hot tub sounds so good😍

I will just get a big paddling pool and fill it up for the kids for free! 

Can't wait to abuse the extra power too😍


16kw Samsung TDM ASHP. 8.4kw PV, power optimizers 20×420watt panels 6kw SolarEdge inverter.


   
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 ronin92
(@ronin92)
Estimable Member Member
Joined: 4 years ago
Posts: 64
03/04/2023 10:28 pm  

More evidence that the EPC regime is not fit for purpose

The over-prediction of energy use by EPCs in Great Britain: A comparison of EPC-modelled and metered primary energy use intensity

Abstract

This analysis compares the difference between the Energy Performance Certificate (EPC)-modelled and smart-meter measured annual energy use on a like-for-like basis in 1,374 gas-heated British households from the Smart Energy Research Lab (SERL) Observatory. EPCs and metered energy use were converted to primary energy use intensity (PEUI) to provide a comparison of the same quantity for the first time.

We show that EPCs predict significantly more energy use than metered in homes in Great Britain. EPC bands A and B show no statistically significant difference, but all other bands show a significant gap which increases as EPC rating worsens. The PEUI gap widens from −26 kWh/yr/m2 (−8%) for band C to −276 kWh/y/m2 (−48%) for bands F and G. Unlike previous research, we show that the difference persists in homes matching the EPC-model assumptions regarding occupancy, thermostat set-point and whole-home heating; suggesting that occupant behaviour is unlikely to fully explain the discrepancy.

EPCs are a core tool in the residential energy sector, and the gap between EPC-modelled and metered energy use could have a significant impact on policy, research, and industry. Future research should investigate disaggregated components of energy use, the underlying thermal model, and assumptions regarding building characteristics.

Link



   
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