UK S.I. 2021/1391 Part L: Solar PV & Energy Regulations Guide
Updated 6 September 2026 · By SolarNevs Research Desk, Dealer surveys + verified sources · 1 source · Method ↗
Key Takeaways
- Statutory Instrument S.I. 2021/1391 (The Building Regulations etc. (Amendment) (England) Regulations 2021) took effect on 15th June 2022.
- Enacted by the Secretary of State under Section 14(3) of the Building Act 1984 following consultation with the Building Regulations Advisory Committee.
- Introduces Regulation 26C establishing mandatory Target Primary Energy Rates (TPER) for all new buildings erected in England.
- Legally defines a "system for on-site electricity generation" as a system producing electricity with a direct electrical connection to the building.
- Regulation 44ZA mandates formal testing, adjustment per manufacturer instructions, and local authority notification within 30 days.
Statutory Scope of S.I. 2021/1391
Under the Building Act 1984, S.I. 2021/1391 enacts the Part L 2021 uplift across England. It amends the Building Regulations 2010 to drive down carbon emissions and primary energy consumption across residential and non-domestic buildings.
The regulations require compliance across two complementary performance metrics: the Target Emission Rate (TER) and the newly created Target Primary Energy Rate (TPER).
Regulation 26C Target Primary Energy Rates & On-Site Solar
Under Regulation 6 of the statutory instrument, Regulation 26C is inserted into the Building Regulations:
Regulatory Provision | Statutory Requirement & Definition | Compliance Impact |
|---|---|---|
Regulation 25 Amendment | Sets minimum energy performance requirements in the form of target primary energy rates | Establishes dual carbon and primary energy caps |
Regulation 26C (TPER) | New buildings must not exceed the target primary energy rate calculated under approved methodology | Mandates on-site low-carbon generation like solar PV |
On-Site Generation Definition | System producing electricity with a direct electrical connection to the building in question | Encompasses rooftop and building-integrated PV arrays |
Primary Energy Concept | Energy from renewable/non-renewable sources undergoing no prior conversion process | Values direct on-site renewable kilowatt-hours |
Regulation 44ZA Commissioning & Local Authority Notification
Regulation 44ZA establishes strict commissioning protocols for on-site solar and storage equipment:
- Scope: Applies to systems for on-site electricity generation installed in new or existing buildings.
- Manufacturer Testing: The person carrying out the work must test and adjust the system in accordance with manufacturer instructions.
- Notification Timelines: Notice must be submitted to the local authority upon completion, or within 30 days of completion if certified under an approved competent person scheme.
Frequently asked questions
When did S.I. 2021/1391 come into force in England?
The Building Regulations etc. (Amendment) (England) Regulations 2021 came into force on **15th June 2022** under the statutory authority of the Building Act 1984 (August 2026).
What new compliance metric is introduced under Regulation 26C?
Regulation 26C mandates that new buildings must not exceed the Target Primary Energy Rate (TPER) calculated using the approved national methodology under Regulation 25 (August 2026).
How is a 'system for on-site electricity generation' defined in the regulations?
A system for on-site electricity generation is defined as a system that produces electricity and has a direct electrical connection to the building in question (August 2026).
What commissioning notice deadline applies under Regulation 44ZA?
Notice that on-site electricity generation has been commissioned must be given to the local authority not later than completion, or within **30 days** under an approved competent person scheme (August 2026).
References
- legislation.gov.uk: S.I. 2021/1391 — accessed 31 August 2026
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