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Future Homes Standard: What the New Solar PV Requirement Actually Demands, And When You Will Really Be Building Under It
Solar PV requirements for new build residential property under Part L 2026 is described in section L3. L3 does not specifically and legally state that solar PV must be installed on every new home, but it does state a system for on-site renewable electricity generation is required, with solar PV being the practical route for most developments.
This article is general guidance, not project-specific advice, though we will be looking into sample projects in future issues.
KEY TAKEAWAYS
- The requirement in Part L 2026 is for on-site renewable electricity generation, not necessarily solar PV.
- The benchmark uses 0.22 kWp/m² across an area equivalent to 40% of the ground-floor area.
- SAP 10.3 is used to calculate the equivalent annual output currently; HEM is due to be released in the coming years to replace SAP 10.3.
- North-facing and overshaded roof slopes cannot simply be excluded.
- Detached garages are excluded from the area calculations, although PV may be installed on one in some circumstances.
- Schemes of 10 or more homes not already in planning should design for the Future Homes Standard now.
Tucked among the changing rooflines of a South of England housing scheme, the solar requirement can look like a simple panel-counting exercise. It is not. Orientation, roof geometry, shading, architectural features, maintenance access, planning constraints and the wider Part L model all need to be resolved before the technical design is fixed.
The Challenge
The Future Homes Standard introduces Requirement L3 into the Part L Building Regulations for England. When a building is built, a system for on-site renewable electricity generation must be installed on the building or within its curtilage.
The system must make electricity available for occupants and be capable of generating a reasonable output, taking account of the building’s design and surroundings.
This is where the problems start. Developers want roof form to include dormers and rooflights to maximise internal floor space, the addition of dormers and rooflights restricts the useable roof area for Solar PV. Part L requires the design to provide a credible renewable electricity strategy. We envisage a conflict between sufficient floor pace to make and building financially viable and the requirement for Solar PV
Our Approach
The Future Homes Standard introduces Requirement L3 into the Part L Building Regulations for England. When a building is built, a system for on-site renewable electricity generation must be installed on the building or within its curtilage.
The system must make electricity available for occupants and be capable of generating a reasonable output, taking account of the building’s design and surroundings.
This is where the problems start. Developers want roof form to include dormers and rooflights to maximise internal floor space, the addition of dormers and rooflights restricts the useable roof area for Solar PV. Part L requires the design to provide a credible renewable electricity strategy. We envisage a conflict between sufficient floor pace to make and building financially viable and the requirement for Solar PV
Our Approach
Start with the benchmark, then calculate the annual output
For a dwellinghouse, Approved Document L Volume 1 describes a reference photovoltaic array with:
- Panel efficiency of 0.22 kWp per square metre.
- An installed area equivalent to 40% of the dwellinghouse’s ground-floor area.
- An orientation from south-east to south-west.
- A pitch of 45 degrees.
- No overshading.
The 0.22 kWp/m² figure is applied to the equivalent panel area. For example, a 50m² ground-floor area produces a reference peak-power figure of:
50m² × 40% × 0.22 kWp/m² = 4.4 kWp
That figure is not the final annual generation value, but the peak installed kW. This is the sum of panel watt power and the number of panels
For buildings containing multiple dwellings, the calculation can be based on the building ground-floor area or the area allocated to individual dwellings, depending on the route used in Approved Document L.
Model the wider Part L position early.
Properly coordinated SAP calculations are key, the renewable electricity generation requirement mainly influences the dwelling’s Emission Rate (DER) and Primary Enegry (DPER) result within the SAP model, rather than replacing the need for a sound fabric efficiency (DFEE). If the annual output cannot be achieved, the shortfall will usually need to be recovered elsewhere in the SAP or HEM model through a different mix of measures. That is why the roof design and renewable strategy are best resolved at design stage, not left until as built stage.
Test the roof before the planning and technical design are fixed
A realistic roof review should identify:
- Roof orientation, pitch and usable areas.
- Dormers, rooflights, vents, flues and plant.
- Shading from neighbouring buildings, trees and landscaping.
- Party-wall, ridge, eaves and verge offsets.
- Planning or conservation restrictions.
The requirement is not satisfied simply by drawing panels on a roof plan. Where the benchmark cannot be achieved, the team must show that the maximum reasonably practicable capacity and annual generation have been provided.
Be careful with north-facing and overshaded roofs. The MHCLG FAQ confirms that lower output from these slopes is generally accounted for within the approved calculation methodology. That is not, by itself, enough reason to leave them out.
Coordinate PV with glazing and overheating
PV design should not be separated from the rest of the building physics.
Glazing affects solar gains and heat loss and overheating risk. Roof design affects PV output, ventilation routes and maintenance access.
We advise coordinating PV layouts with Part O overheating assessments rather than treating them as separate steps. The right mix of measures will depend on the house type, orientation, construction and services strategy.
Do not use PV to conceal weak fabric design
The L3 requirement is not a substitute for a robust fabric strategy. The Future Homes Standard still requires the dwelling to meet its wider Part L targets.
Our approach is to model and coordinate:
- U-values and glazing performance.
- Thermal bridging psi values.
- Airtightness achievable result.
- Heating and hot-water systems.
- Ventilation and Part F requirements.
- PV generation
- As-built evidence and commissioning.
The Outcome
When will most developers really build under the Future Homes Standard?
For non-higher-risk work, the 2026 amendments generally will not apply where:
- A building notice, initial notice or application for building control approval with full plans was submitted before 24 March 2027; and
- Work on that particular building is commenced before 24 March 2028.
The test applies per building, not per site. An early application for one block, plot or phase does not automatically protect the rest of a development.
For a new dwelling, commencement is also more demanding than simply starting work. The sub-surface structure must be completed, including all foundations, any basement and the ground-floor structure. Site clearance, enabling works, demolition, or the start of drainage and general groundworks do not count.
A practical programme timeline.
- Now to early 2027: Submit building regulations applications and programme start if the particular buildings can realistically reach the required construction milestone.
- 24 March 2027: The new requirements take effect for non-higher-risk work that is not protected by transitional provisions.
- 24 September 2027: The relevant requirements take effect for higher-risk building work, subject to its separate transitional arrangements.
- 24 March 2028: Final start date for the principal non-higher-risk transitional route.
If a development of 10 or more homes is not already in planning, it is likely to be designed and built under Part L 2026. Planning determination, technical design, condition discharge, procurement and mobilisation can easily run beyond the available window.
The practical conclusion is simple. For many schemes not yet in planning, it makes sense to design on the basis that the Future Homes Standard will apply.
Why It Matters
The new PV requirement affects more than adding some panels to the roof. It can influence roof forms, planning drawings, house types, landscape design, maintenance arrangements, overheating assessments and the commercial viability of a scheme.
It also affects the timing of energy statements for planning. If the renewable strategy is left until building control, the team may find that the roof cannot accommodate the required output without changes to the architecture or planning assumptions, potentially requiring planning redesign.
FAQs
What does L3 require?
It requires on-site renewable electricity generation for a building that is or contains one or more dwellings. The system must be on the building or within its curtilage, make electricity available to residents and provide a reasonable output for the building and its surroundings.
Is solar PV compulsory?
No. The legal requirement is for on-site renewable electricity generation, not solar PV specifically. In practice, PV is likely to be the practical route on many schemes.
How is the output benchmark set?
The benchmark uses 0.22 kWp/m² over an area equal to 40% of the relevant ground-floor area. Annual output is then calculated using SAP 10.3, including Appendix M1.
What if the benchmark does not fit?
The design should use the reasonably practicable roof area and maximise generation. The shortfall then has to be addressed elsewhere in the SAP or HEM model, which is why the roof and renewable strategy are better resolved early.
Can shaded or north-facing slopes be ignored?
No, not automatically. Their lower output is generally accounted for in the approved methodology, so that alone is not enough reason to exclude them.
Do detached garages count?
No. Detached garages are excluded from the ground-floor area and reasonably practicable roof area calculations. PV may still be installed on one within the curtilage if the requirement is met.
Are there exemptions?
Yes. L3 does not apply to relevant buildings under regulation 7(4), which generally includes buildings over 18 metres containing dwellings or residential rooms. There may also be cases where no reasonable renewable output is possible because of the design or surroundings, or where equivalent renewable generation is available to residents from another qualifying source.
Are listed buildings exempt?
No, not automatically. Compliance is required so far as reasonably practicable without unacceptably altering character or appearance.
When does L3 apply?
For non-higher-risk work, it applies from 24 March 2027. For relevant higher-risk work, it applies from 24 September 2027, subject to the relevant transitional arrangements.
Do transitional provisions cover L3?
Yes, generally. If the 2026 amendments do not apply to work on a particular building under the transitional provisions, the new L3 requirement will generally not apply to that protected work either.
Official sources
• Approved Document L, Volume 1: Dwellings, 2026 edition
• MHCLG Approved Document L: Energy and greenhouse gas emissions FAQs
• The Building Regulations etc. (Amendment) (England) Regulations 2026
As with the rest of Part L 2026, the notional and legal positions should be verified against the current Approved Document L before a specification is committed.
If you are reviewing a South of England scheme of around 10 to 50 homes, we can review the fabric, PV strategy, airtightness, thermal bridging and SAP together before the design is fixed.
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