Desk with Laptop, Calculator, Files and small model of house with epc colours
Desk with Laptop, Calculator, Files and small model of house with epc colours
EPC Works
EPC Works

Solar PV & Home Batteries

At the time of writing the methodology for EPC assessments of existing dwellings is RDSAP 9.94. The much anticipated RDSAP 10 update is due in Q1 2025 and a significant methodology overhaul from RDSAP to the Home Energy Model (HEM) is proposed for 2026.

Solar PV

When solar photo-voltaic panels are exposed to sunlight, they generate electricity which can be fed into your property to offset your electricity use.

 

These panels are in contrast to the other type you may occasionally come across called Solar Thermal panels. Solar Thermal panels contain pipes through which water is heated by the sun and circulated to heat up water stored in a Hot Water Cylinder.

 

Solar Thermal panels have fallen out of favour, with preference now generally given to Solar PV panels instead, the price of which has fallen in recent years.

 

Solar PV could be a 'get out of jail' card for your property if you need to improve your EPC rating for current MEES requirements (this will change from 2028 onwards however).

Recommendation Triggers

Solar PV is often listed as a recommendation on EPCs to improve your rating, and the gains can be fairly significant.

 

In order to be listed as an improvement measure on an EPC, the following are required:

  • The property needs to be a House or a Bungalow
  • The property must not have a thatched roof
  • There must be no photovoltaics currently present at the property

If Solar PV is displayed on an EPC as a recommendation then 2.5kWp is the level used for the indicated EPC rating improvement, although you can install as much as your property can accommodate.

Recording the presence of Solar PV

When an energy assessor records the presence of Solar PV at your property they would ideally like to see the MCS Certificate you were provided with at the time of installation.

 

All solar PV installers need to be registered with the Microgeneration Certification Scheme (MCS), and the certificate they provide will detail the capacity of the Solar Installation (in kWp), the orientation and the elevation of the panels.

 

This information is useful for the EPC assessment. If it is not available then the Domestic Energy Assessor can instead enter some generic information about the installation but the information will not be as accurate as that provided by an MCS certificate.

Example EPC Rating Improvements

Let's take a look at what difference Solar PV makes to my property, a 1950s mid-terraced 3-bed house with a gas condensing boiler, no cavity wall insulation, and 200mm loft insulation (We cover this property in our Case Study 2). The base EPC rating is currently 68D:

Description EPC Rating Increase
No Solar 68D -
2.5kWp - North Facing 75B +7
2.5kWp - South Facing 81B +13
6.0kWp - North Facing 86B +18
6.0kWp - 50% each North/South 92A +24
6.0kWp - South facing 99A +31
9.0kWp - 50% each North/South 105A +37

The above illustration uses panels mounted with a 45 degree angle, and with 'no or low overshading'.

 

Solar PV clearly makes a considerable difference to the EPC rating for this property, particularly if the panels are South facing.

 

Considering it's a bordeline band D/C property, even with only 2.5kWp on a South facing roof, an increase to a 81B would be a large increase.

 

Just to demonstrate that EPC ratings with a SAP score of 100 or more are possible, the final line in the table is for 9.0kWp split 50% North and South, we get an EPC rating of 105A.

 

As a guide, 6.0kWp would be quite a large amount of solar for a typical 3-bed semi. Most installations would be smaller than that.

 

The EPC rating gain is dependant on various aspects of a particular property, so always consult an energy assessor before fitting Solar PV, to understand the rating you could achieve with your property.

Home Batteries

Home batteries allow you to store up electrical energy at times when cheap electrical energy is available to you.

 

This could be electricity you have generated 'for free' from your solar panels, or you could draw it from the national grid at night time (or other times dependent on your tarrif) when cheap rate electricity is available.

 

You can then consume that stored electrical energy at times when you need it, or when it would be more costly to have drawn it from the main electriciaty grid instead.

 

Unfortunately, at the time of writing home batteries cannot be included within an RDSAP EPC - that's the type of EPC used for an existing dwelling, rather than a new build.

 

There is a methodology update to RDSAP due soon under which Home Batteries can be recorded, but it keeps getting delayed.

 

Version 10 of RDSAP, will support the recording of home batteries within an EPC assesment, but only when solar PV is also present at the property.

 

If you have a Home Battery installed on its own, ie without solar, then unfortunately you will still not be able to include it in the EPC assessment.

 

If you woud be able to include your home battery (because you also have solar), then the home battery should improve the rating of your EPC. By how much we will have to wait and see.

 

If you have solar and a home battery currently, you might be interested in getting another EPC conducted once RDSAP 10 has been released. It's currently suggested for Q1 2025 release.

 

 

Click here to return to our 'Improve Your EPC' main page, and see if there is another way you could improve your EPC rating.


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