Solar Panel and Renewable Energy Requirements

What This Requirement Covers

Renewable energy systems, particularly solar photovoltaic (PV) panels, are increasingly used to meet the carbon emission targets in Approved Document L. While Part L does not mandate specific renewable technologies, the carbon emission targets for new dwellings under the 2021 edition are set at levels where some form of renewable energy generation is typically needed to comply.

Key Requirements

Solar PV

1. Solar PV generates electricity from sunlight
2. A typical domestic installation is 3-4 kWp (kilowatt peak), requiring approximately 8-12 panels and 15-25 m² of unshaded, south-facing roof area
3. Generation is calculated in SAP using the system size, orientation, pitch, and shading
4. Solar PV is the most cost-effective renewable technology for achieving Part L compliance in most situations

Solar Thermal

1. Solar thermal panels heat water directly using sunlight
2. A typical domestic installation comprises 2-4 m² of panels and a twin-coil hot water cylinder
3. Solar thermal is less commonly installed than solar PV due to higher costs and the need for a compatible cylinder
4. SAP gives credit for solar thermal contributions to hot water heating

Other Renewable Technologies

1. Small wind turbines: Rarely practical in urban or suburban locations due to turbulence and low wind speeds
2. Biomass boilers: Use wood pellets or logs; produce CO2 but at a lower rate than fossil fuels. May be appropriate in rural areas
3. Micro-CHP (combined heat and power): Generates electricity and heat simultaneously; limited market availability

Permitted Development

1. Solar PV on a dwelling roof is generally permitted development, subject to:

- Panels not projecting more than 200 mm from the roof plane - Panels not exceeding the highest point of the roof (excluding the chimney) - Not on a listed building or within the curtilage of a listed building without consent - Not on a wall fronting a highway in a conservation area

1. Ground-mounted solar arrays must not exceed 9 m² in area and 4 metres in height

Financial Incentives

1. Smart Export Guarantee (SEG): Energy suppliers with more than 150,000 customers must offer a tariff for exported electricity from domestic solar PV systems up to 5 MW
2. VAT relief: Solar PV and energy storage installations on domestic properties benefit from 0% VAT (until March 2027)
3. Boiler Upgrade Scheme: Does not cover solar PV but can be combined with heat pump grants

Practical Compliance Tips

1. Model solar PV in the SAP calculation early to determine the system size needed for Part L compliance
2. Maximise the south-facing, unshaded roof area available for panels at the design stage
3. Consider battery storage to maximise self-consumption of generated electricity
4. Ensure the roof structure can support the additional weight of solar panels (typically 15-20 kg/m²)
5. Install cable routes from the roof to the consumer unit during construction rather than retrofitting
6. Solar PV inverters have a typical lifespan of 10-15 years and will need replacement during the life of the panels (25-30 years)
7. Register the installation with the MCS scheme to qualify for the Smart Export Guarantee