Part L 2026 PV requirements - FAQs

Since the new Approved Document Part L (the Future Homes Standard) was published, there's been uncertainty about the specifics of the new PV Functional Requirement. 

We now have answers to some of those Frequently Asked Questions from the Ministry for Housing, Communities and Local Government (MHCLG):

🔗 https://www.gov.uk/guidance/approved-document-l-energy-and-greenhouse-gas-emissions-frequently-asked-questions

The new Part L (2026) requires mandatory PV panels, but there is some confusion around the smallprint of the new regulations.

In summary:

❓ How is an 'appropriately sized' PV array defined?

Consider the energy demand of the dwelling, the capacity of the network and possible export limits.

If there’s good reason to install less than 40%, discuss with the Building Inspector.

❓ How do I calculate the PV Functional Requirement?

Get a SAP assessor to do it.

❓ How do I calculate the efficiency of a PV panel?

Ask your PV supplier.

❓ Do I need to consider PV on all roofs, including north facing and heavily shaded roofs?

Yep.

❓ How do you define the 'building curtilage' for installing PV?

Essentially any suitable space within the plot boundary.

❓ Can PV systems in apartments feed into a Landlord Supply?

Yep, but residents must receive some kind of benefit from the PV (not specifically financial benefit).

❓ Is the area of a detached garage included in the PV 40% calc?

Nope.

❓ Can I install PV on the detached garage anyway?

Yep

❓ Do I have to follow the PV spacing distancing guidance in Part L1, Appendix B?

Not if you've got a better way of measuring it.

Hopefully, we'll get further clarification on other topics before the regs go live next March.