The Welsh Government issued circular WGC 003/2026 on 6 March 2026, drawing attention to the Building etc. (Amendment) (Wales) Regulations 20261. The circular is marked "For information" and was issued by Paul Keepins, Building Standards Technical Manager, to local authority chief executives, building control bodies and industry bodies1. The regulations apply to buildings and building work in Wales1.
The energy efficiency amendments to Part L of Schedule 1 to the Building Regulations 2010 come into force on 4 March 20271. They amend the definition of "fixed building services" to include fixed lifts, escalators or moving walkways in new buildings, but not in individual dwellings; revoke two regulations on nearly zero energy buildings and consideration of high efficiency systems; replace references to "energy efficiency rating" with "energy use intensity rating"; amend the Part L title to recognise that the requirements also reduce greenhouse gas emissions; and add a requirement that when a dwelling, or a building containing a dwelling, is erected, a system for renewable electricity generation must be installed on-site1.
Solar Energy UK said the change means Wales "will become the first part of the UK to effectively require new buildings to have solar panels fitted as standard"2. The regulations do not name solar power; the trade body states that the requirement for a renewable electricity generation system means rooftop solar will be deployed in virtually every circumstance, as the cheapest and most practical way to comply2. Solar Energy UK reports that if a system capable of generating at least 720 kilowatt-hours per year cannot be installed, the requirement will not apply, and that the rules assume homes would be unable to supply more than 16 amps per phase, or 3.68kW, to the grid, with permission from the regional distribution network operator required beyond that level via a G99 application2. It adds that installing more than the minimum will count towards meeting energy efficiency requirements and achieving a higher energy performance certificate rating2.
"This is tremendous news for Wales and I applaud the Welsh Government for their wise decision. Solar Energy UK has long lobbied for solar power to be all but mandatory on new homes and buildings, which will soon see far lower bills than would otherwise have been the case."
Separately, amendments relating to the implementation of the Building Safety Act 2022 come into force on 1 July 20261. These require a person submitting an Initial Notice to inform the local authority that they have previously received a contravention notice in relation to the work that was not remedied, and give details of it, and give local authorities additional grounds to reject an Initial Notice where a contravention notice was not addressed1. The circular states the amendments are intended to stop individuals avoiding enforcement by switching registered building control approver after receiving a contravention notice1. The checking of plans for higher-risk buildings remains a restricted activity1.
| Change | In force |
|---|---|
| Part L energy efficiency amendments (regulation 3) | 4 March 20271 |
| Building Safety Act 2022 implementation amendments (regulations 4 to 7) | 1 July 20261 |
Why it matters for households
For a household in Wales, the practical effect falls on new-build homes rather than existing ones. A new dwelling will need an on-site renewable electricity generating system, which in practice is expected to mean rooftop solar2. That changes the energy profile of a new home from the point of construction: generation on the roof rather than purchase from the grid, and a route to lower running costs where the system is sized above the minimum2. The shift from an "energy efficiency rating" to an "energy use intensity rating" changes the metric against which a dwelling's performance is measured1, which affects how a home's energy demand is described in assessments.
The rules do not apply retrospectively to work already under way. The circular states the regulation 3 amendments do not apply to building work that has commenced, or where certain notifications have been made, provided the work on that building has already commenced or is started within 12 months of the regulations coming into force1. Where a site has several buildings, only those individual buildings for which work is commenced can use the transitional provisions1. Solar Energy UK reports that from a year after the March 2027 start, the requirement will also extend to works covered by building control approval, such as installing a new roof or renovations for a material change of use2.
What happens next
Amended Approved Documents L volume 1, L volume 2 and F volume 1 will be available on the Welsh Government website in spring or summer 2026, and will be subject to a separate circular when published1. Solar Energy UK states that revised guidance setting out the finer details will come in the spring or summer, following a consultation last autumn2. The Building Safety Act 2022 amendments take effect on 1 July 2026, and the changes will not apply to work where building control approval has been sought before that date1.