Forums

Forums
Renewable Heating
Air Source Heat Pum...
Predicted Heat Loss...
 
Notifications
Clear all

Predicted Heat Loss & Needs from MCS calcs vs EPC vs actual

 
Air Source Heat Pumps (ASHPs)
Last Post by Tim441 11 hours ago
2 Posts
1 Users
0 Reactions
39 Views
RSS
 Tim441
(@tim441)
Noble Member Contributor
Joined: 3 years ago
Posts: 381
Topic starter 10/01/2026 7:36 pm  

LG therma V installed 2020. 16kw monobloc. Initially on fixed flows then weather compensation 

Looking back at the info from design in 2020

EPC 2020 predicted
The annual Space Heating requirement for your property is: 19,242kWh The annual Hot Water requirement for your property is: 2,997kWh

MCS 2020 predicted:
The annual Space Heating requirement for your property is: 23,776kWh The annual Hot Water requirement for your property is: 3,957kWh
Based on fixed flow temp 50deg

A difference of almost 5500kWh

Recent EPC 2025 predicted
32,443 kWh per year for heating
3,283 kWh per year for hot water
Total 35,726kWh!!

Actual metered heat pump usage was just over 8000kWh for the first 2 years on fixed flows and 5800kWh for the next 3 years on weather compensation.

At a total guess average COP across heating and hot water is 3? So my true heat loss & hot water requirement is probably in the region of 18000kWh (half the recent epc prediction!!!)

We heat main areas of the house to 21deg but bedrooms and lesser used rooms are much cooler. We normally have only 2 living at home so hot water usage is lower thsn predicted. 

All the same it shows huge differences.

I think its a depressing example of the value of all these calcs. I'm sure there are other examples which are much closer to reality?


This topic was modified 11 hours ago 4 times by Tim441

Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV


   
Quote
Topic Tags
Heat loss mcs epc
 Tim441
(@tim441)
Noble Member Contributor
Joined: 3 years ago
Posts: 381
Topic starter 10/01/2026 7:52 pm  

My gut feeling is that the heat pump is right sized.

  • it does not seem to cycle
  • It heats the house comfortably
  • costs/usage seems reasonable - especially against predictions by EPC or MCS
  • the spare capacity would probably allow us to heat all rooms to 21deg if we wanted to 

 


Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV


   
ReplyQuote
Forum Jump:
  Previous Topic
Next Topic  
Related Topics
Topic Tags:  Heat loss (6) , mcs (5) , epc (3) ,

Currently viewing this topic 1 user ( Tim441 ) .

Share:

Join Us!

Worth Watching

Latest Posts

Click to access the login or register cheese
x Powerful Protection for WordPress, from Shield Security
This Site Is Protected By
ShieldPRO →