The Future Buildings Standard introduces a mandatory solar PV requirement for new non-domestic buildings. The FBS policy sets the notional PV area at a flat 40% of foundation area for both side-lit and top-lit zones (consultation response, para 3.11, p18). The current NCM 2021 still uses a weighted formula - 20% side-lit / 40% top-lit (NCM 2021, Equation 9) - which the 2026 NCM will update to match the flat 40% policy. Use this calculator to find the minimum PV array size and estimated capacity for your project, and check whether any exemptions apply.
Step 1: Enter the building foundation area
How this tool works
The calculator uses the FBS policy of a flat 40% of foundation area for all zone types (consultation response, para 3.11, p18). Note: the current NCM 2021 uses a weighted formula - 20% side-lit / 40% top-lit (Equation 9) - but the 2026 NCM will adopt the flat 40%. The estimated kWp capacity is calculated at 0.2 kWp per m² of array (NCM 2021, para 81). If 100% of heating is from heat pumps, the notional building has no PV (NCM 2021, para 83).
Two categories of building may be exempt from the solar PV requirement:
- Higher-risk buildings (HRBs) are fully exempt, reflecting the practical and safety constraints of PV installation on tall buildings.
- Listed buildings and buildings in conservation areas may be exempt where PV installation would unacceptably alter the character or appearance of the building or area.
The PV requirement in the notional building sets a minimum. The actual SBEM calculation may indicate that additional renewables are needed to meet the target emission rate (TER) and target primary energy rate (TPER).
Related Pages
Solar PV Requirements
Full guide to the FBS solar PV requirement, exemptions, and how it interacts with SBEM.
Notional Building Lookup
Look up notional values for every building element under the FBS and Part L 2021.
Notional Building Specification
How the notional building works in SBEM and what it means for compliance.