@ronin92 that's a good find, thank you. Having had a speed-read of the research paper, it seems the elephant in the room may be the simple affordability of heating houses assigned lower EPC gradings E, F & G. That could be a significant aspect of the predicted vs actual metered energy consumption. Chances are the thermostats are set lower in such buildings, more rooms are left unheated, and the occupants accept lower levels of thermal comfort as a price to pay for being able to manage the cost of very expensive gas and electric they consume. EPCs do not factor any of this into the SAP calculation method.

The EPC process is deeply flawed, and whole house permeability/leakage tests are not mandated in the survey method. That alone can be grossly under or overestimated, especially for properties more exposed to the elements. It is almost as significant a factor as the U values of the building fabric, especially for older 'draughtier' properties.

This matters, because domestic EPCs are a legal requirement for the sale, purchase and letting of property. Also more and more access to grant funded schemes including BUS is linked to EPC grading. The BRE domestic SAP process is deeply flawed for assessing dwellings with heat pumps:

YORKSHIREENERGYSYSTEMS.CO.UK "https://www.yorkshireenergysystems.co.uk/epcandheatpumps/"

@allyfish

Hi Everyone,

Rather than just discuss this problem on the forum, I would encourage you to write to your MP and ask what is being done to rectify this problem. Below is a copy of the message that I sent today.

Hi Andrew,

A number of forum members on the Renewable Heating Hub, of which I am a moderator, have highlighted the fact that recent EPC assessments have been lower than anticipated because they had installed an ASHP.

One of the members posted this report, which although quite dated, was highlighting this problem approximately 8 years ago.

YORKSHIREENERGYSYSTEMS.CO.UK "https://www.yorkshireenergysystems.co.uk/epcandheatpumps"

Could you please explain what, if anything, is being done to remedy this obvious problem, since the Government is trying to encourage homeowners to install energy efficient heating systems such as heat pumps. It would appear that the present EPC assessment methodology is seriously flawed, and needs urgent revision.

Another forum member installed an Air to Water heat pump himself, and found that the cost of all the materials and equipment, along with a sufficient allowance for labour costs, produce a figure that was approximately £5000 less than the quotes from a number of installers. I strongly suspect that the BUS grant of £5000 is not actually benefiting homeowner's, but is instead going into the pockets of the installers.

I can confirm the same, as approximately 2 years ago I installed an Air to Air ASHP at our home myself, which does not qualify for the BUS grant, but since the equipment and materials (excluding my labour) came to less than £1000, not getting a grant was of little consequence. My primary objective was to better utilise the excess electricity generation from our 4kW solar PV system, and in so doing reduce our overall gas consumption by something in the order of 50%. As I write this, our home is being heated completely by solar energy, which has been the case since approximately 8 am today, and will probably continue to do so until after midnight.

Even during Spring and Autumn there is a great deal of solar energy available, we human's just need to get much better at capturing and utilising it in the most efficient manner.

I look forward to your reply.

Regards,

Derek.