Solar Panels on Your Home: Permitted Development, Building Regs, and What to Know

Under the Town and Country Planning (General Permitted Development) (England) Order 2015 (Schedule 2, Part 14, Class A and Class B), solar PV and solar thermal panels can be installed on a dwelling without planning permission provided the following conditions are met:

• **On a pitched roof (Class A)**:
• •The panels must not protrude more than 200mm beyond the plane of the roof surface
• •When installed on the principal elevation (front of the house), panels must not be visible from the highway — this effectively means front-elevation panels on most terraced and semi-detached houses require planning permission
• •Panels on the roof slope facing the rear garden (rear roof slope) are almost always Permitted Development
• •The panels must not exceed the highest point of the existing roof

• **On a flat roof (Class B)**:
• •Panels must not protrude more than 1.0m above the flat roof deck when positioned upright
• •Panels must be set back from the edge of the flat roof
• •Panels must not be installed on the principal elevation visible from the highway

**Conservation Areas (Class A and B)**: Within a Conservation Area, solar panels on the roof slope or flat roof that are 'visible from a highway' are NOT Permitted Development and require a planning application. Because Conservation Areas are typically defined by their street-visible character, this restriction in practice covers most installations on front and side roof slopes in Conservation Areas. Rear roof slope installations within Conservation Areas are typically Permitted Development (not visible from the highway) — but check the specific Conservation Area's characteristics.

**Listed Buildings**: Any installation of solar panels on a listed building requires Listed Building Consent in addition to planning permission (or confirmation that Permitted Development applies). Listed Building Consent is required because solar panels are a material alteration to the building's external appearance. Many heritage officers are willing to support sensitively designed rear roof slope installations that do not affect the listed building's character — but each case must be assessed individually.

Solar PV and solar thermal installations are subject to Building Regulations in several respects:

• **Part A (Structure)**:
• The structural integrity of the roof must be assessed before solar panels are installed. Solar PV panel arrays add approximately 10–15 kg/m² to the roof load (plus the additional load of the mounting system). For most modern houses with a tile-on-batten-on-sarking roof structure, this additional load is within the structural capacity of the roof. However:
• •Older roofs with undersized rafters, spreader plates missing, or existing structural deficiency may not be adequate — a structural engineer's assessment is advisable before specifying large arrays
• •Flat roof PV systems on ballast mounts add greater point loads — structural engineer assessment is typically required for ballasted systems on flat roof extensions

**Part J (Combustion appliances) / Part L (Conservation of fuel and power)**: Solar PV is a 'fixed building service' under Part L. While a solar PV installation on an existing dwelling does not itself trigger a Building Regulations application, Part L does require that installations are carried out to achieve the specified CO₂ performance benefits — this is generally met by compliance with the MCS (Microgeneration Certification Scheme) standard.

**Electrical works (Part P)**: The electrical installation connecting the solar PV panels to the house distribution board must be carried out by a Part P-registered electrician or must be notified to and inspected by Building Control. In practice, MCS-accredited solar installers are almost always Part P-registered and self-certify.

**MCS (Microgeneration Certification Scheme)**: For solar PV installations to qualify for the Smart Export Guarantee (SEG) — the scheme under which export of surplus electricity to the grid earns a payment — the installation must be MCS-certified. MCS certification covers both the installer and the equipment. Always use an MCS-accredited installer to retain eligibility for SEG payments and any future government support schemes.

• A solar PV system generates electricity when the panels are irradiated by daylight (not just direct sunlight — diffuse daylight also generates electricity, though at lower output). The system can:
• •Supply the house directly (self-consumption)
• •Export surplus to the National Grid (via the grid connection)
• •Charge a battery storage system for use when the panels are not generating

**Grid connection**: Connection to the grid is straightforward for most domestic solar PV systems (up to 16A per phase, or approximately 3.68kW single-phase). The installer notifies the District Network Operator (DNO) and arranges the grid connection. For larger systems (over 16A per phase), G99 or G100 connection agreements are required from the DNO — this involves more assessment time but is not typically a barrier for residential installations.

• **Smart Export Guarantee (SEG)**:
• From January 2020, energy suppliers with over 150,000 customers are required to offer SEG tariffs — payments for electricity exported to the grid from MCS-certified generators under 5MW. SEG rates vary by supplier and tariff type:
• •Flexible SEG tariffs: payment varies based on half-hourly wholesale electricity prices — can deliver higher returns when electricity demand (and prices) are high
• •Fixed SEG tariffs: a fixed payment per kWh exported — currently 3–6p per kWh depending on the supplier

SEG rates are lower than the old Feed-in Tariff (FiT) rates that closed to new applications in 2019. However, the business case for solar PV has improved independently of export payments because retail electricity prices have risen significantly since 2021.

• **Battery storage**:
• A home battery storage system (typically 5–15kWh capacity, e.g. Tesla Powerwall, Givenergy, Solis) allows surplus daytime generation to be stored for use in the evening and at night. Battery storage significantly increases self-consumption rates (the percentage of total generated electricity used directly rather than exported):
• •Without battery: self-consumption rate typically 30–40% for a typical household
• •With battery: self-consumption rate typically 60–80%

**Battery storage costs (2025)**: £5,000–£12,000 installed, depending on capacity and system type. VAT on solar PV and battery storage is currently 0% (reduced from 20% in 2022).

• **System sizing for a typical London house**:
• •3-bedroom terrace with rear roof slope: approximately 6–10 panels, 2.5–4.0 kWp capacity
• •4-bedroom semi-detached with dual-aspect roof: approximately 10–16 panels, 4.0–6.4 kWp capacity

**Annual generation in London**: London receives approximately 900–1,000 kWh/kWp of generation per year (lower than the South West but still viable). A 4kWp system generates approximately 3,600–4,000 kWh/year.

• **Solar PV installation costs (supply and install, London 2025, including VAT at 0%)**:
• •3kWp system (6–8 panels): £5,000–£7,000
• •4kWp system (8–12 panels): £6,500–£9,000
• •5–6kWp system (12–16 panels): £8,000–£12,000
• •With battery storage (add): £5,000–£10,000

• **Payback calculation (illustrative)**:
• •4kWp system, 4,000 kWh/year generated
• •50% self-consumed (2,000 kWh × 30p/kWh = £600 saving)
• •50% exported (2,000 kWh × 5p/kWh = £100 SEG income)
• •Total annual benefit: £700
• •System cost (4kWp, no battery): £7,500
• •Simple payback: approximately 10–11 years

With a battery storage system, self-consumption rises to approximately 70–80%, improving annual benefit to approximately £900–£1,000 — but the additional capital cost of the battery means payback extends to 13–16 years in most scenarios.