New data provided by the Microgeneration Certification Scheme (MCS) shows that the proportion of new homes built in England that come with solar PV has more than doubled in the last 12 months.
In the last quarter of 2023 it was estimated that 13% of new homes that completed construction had solar PV fitted by the developer. This figure has risen to 29% in the most recent quarter and will continue to grow as housebuilders in England further transition to the 2021 version of Part L of the Building Regulations.
As the number of new homes with solar PV built by private developers has increased, the average installed power (kWp) per new build installation is falling.
Prior to the new Building Regulations coming into force, solar on new homes was driven by either local planning requirements or fitted by self-builders as a personal preference. Self-builders would size a system for a cost-effective contribution towards their own energy requirements. Solar to meet a planning condition was on a site-wide basis and tended to be concentrated onto a few homes on the development to meet the condition in the most cost-effective way.
By contrast the new Building Regulations apply individually to each plot but once the required energy performance of the building is met, developers generally see little reason to extend a PV system further - resulting in generally smaller PV installations. The effect of this can be seen in the kWp/install column where the average has reduced over the period from 3.8kWp per installation to 2.8kWp.
Also worth noting is that solar on new buildings has risen from being 19% of MCS certified solar installations in England to 34% over the period. As already mentioned, this transition has further to run and I predict that by the end of 2025, new build solar will account for at least 50% of MCS solar installations in the UK.
Notes on the Analysis
The number of new build MCS solar PV installations in the quarter was expressed as a proportion of new build housing completions in the same period to arrive at a percentage of new homes built with solar PV.
When registering a new solar PV installation with the MCS, the installer must tick a box to say whether the installation is on a new building. The brilliant, publicly available MCS data dashboard does not currently allow users to filter the data on this basis, but the team at MCS responded to a request from Solar Energy UK and kindly provided us with the data. I hope this functionality can be added in future.
The MCS certificate is issued only when the system is commissioned, which occurs after second fix. This creates the potential for a timing difference between the MCS data and the data based on practical completion of the building (which may come a few weeks later). The error this creates is mitigated against by aggregating to quarterly data.
It is also worth mentioning that it was not possible to split the MCS new build data into residential and commercial installations, so I have had to assume that the total is all residential, which will result in an over-estimate, but one that reduces as the number of new build homes with solar grows. On the other hand not all solar installations will run through the MCS so this mitigates the over-estimate, as does focusing on the number of installations rather than the installed power (commercial solar tends to be larger systems in lower number).
Data for housebuilding completions is taken from this ONS dataset, which is quarterly, and only available up to Q2 2024. The dataset was extended by one quarter by reference to this NHBC data which was used to scale the figure for Q2 to Q3.
