The Ministry of Housing, Communities and Local Government published a set of frequently asked questions on Approved Document L: Energy and greenhouse gas emissions, 2026 edition, on 8 September 20261. The page applies to England and addresses how the new Requirement L3 for renewable electricity generation interacts with the existing Requirement L21.
Under Requirement L2, where an on-site electricity generation system is installed, reasonable provision must be made to ensure the system and its electrical output are "appropriately sized for the site and available infrastructure", that "it has effective controls", and that it is "commissioned through testing and adjustment so that it produces the maximum reasonable amount of electricity under the circumstances"1. The guidance states that "any system installed to meet L3 must also comply with all other relevant Building Regulations, including L2"1. Factors relevant to judging whether a system is appropriately sized are listed as the on-site energy demand, "the capacity and nature of the available infrastructure, including export limits set by the District Network Operator", the relationship between export limits, generation and on-site demand, and other site characteristics1.
For Requirement L3, the guidance sets out the benchmark for a new dwelling-house: an annual output at least equal to that of a photovoltaic array with installed peak power equal to "photovoltaic panels with an efficiency of 0.22kWp per m2" installed over an area equivalent to 40% of the dwelling-house's ground floor area1. The annual output in kWh is calculated under "M1 Photovoltaics" in Appendix M1 of SAP 10.31. For buildings containing one or more dwellings, AGRND or AGRNDWELL should be used as appropriate for the ground floor area1. Panel efficiency is calculated by dividing the output in kWp by the area of the whole panel, including the frame but excluding flashings1.
The FAQ confirms that north-facing and heavily overshaded roof surfaces must be considered when identifying the "reasonably practicable roof area", and that lower generation from orientation or overshading is unlikely to be sufficient justification to exclude a surface1. Developers are responsible for identifying what constitutes that area and justifying the assessment to the relevant building control body1. Detached garage ground floor area is excluded from the 40% calculation, and the garage roof is excluded from the reasonably practicable roof area, though panels may be installed on a garage roof within the curtilage to meet L31. No panel dimensions are specified for sizing an array; the guidance says developers will in most cases use dimensions consistent with commercially available residential solar panels1.
"the lower generation resulting from an array being located on a north facing roof relative to other orientations is unlikely to be sufficient justification to exclude it from the 'reasonably practicable roof area.'"
Why it matters for households
The document governs new-build homes rather than existing ones, so its direct effect on most households is indirect. For buyers of a new home, it clarifies what solar provision a developer is expected to deliver and on which roof surfaces, which bears on how much of a home's electricity could be generated on site and how much is drawn from the grid. The confirmation that north-facing and shaded roofs count towards the target area means arrays may be spread across less productive surfaces, with the calculation accounting for the resulting lower output. The L2 conditions on sizing, controls and commissioning relate to whether a system works as intended once installed. The guidance also states that generated electricity should be available to residents, including in blocks of flats, where it may serve individual dwellings and communal spaces1. Nothing in the FAQ addresses battery storage, tariffs or the treatment of existing homes, and no such detail has been reported.
What happens next
No further steps or dates are set out in the FAQ beyond its publication on 8 September 20261. The page refers to the Approved Document L: Energy and greenhouse gas emissions (2026) and to Approved Document L1 (2026 edition)1. For the wider framework, see the site's guide to UK home energy regulation and policy and to building regulations in England.