Solar Panel Installation UK
Guide, Requirements & Costs 2026

A domestic solar photovoltaic (PV) system converts sunlight into electricity using semiconductor panels mounted on the roof. The typical UK domestic system is between 3 kW and 4 kW, consisting of 8 to 10 panels each rated at approximately 400-450 W. A south-facing roof at a pitch of 30-40 degrees provides the best energy yield, although east-west split arrays are increasingly common and can provide a more even generation profile throughout the day.

The PV panels generate direct current (DC) electricity, which is converted to alternating current (AC) by an inverter. The AC output is connected to the property's consumer unit, where it supplies the household loads. Any surplus electricity not used by the household is exported to the grid. The system operates automatically — generating electricity whenever there is sufficient daylight — and requires minimal maintenance beyond occasional panel cleaning and periodic inverter checks.

For electricians, solar PV installation involves both DC and AC electrical work, structural assessment of the roof, compliance with MCS standards, DNO notification, and Part P building regulations notification. It is a skilled job that requires specific training and, for SEG eligibility, MCS installer certification.

The Microgeneration Certification Scheme (MCS) is the quality assurance framework for small-scale renewable energy installations in the UK. MCS certification covers both the products (panels and inverters must be MCS-listed) and the installers (who must be MCS-certified). An MCS-certified installation is eligible for payments under the Smart Export Guarantee (SEG), the scheme that pays generators for electricity exported to the grid.

To become an MCS-certified installer, you must hold a relevant qualification — typically the City and Guilds 2399 (Design and Installation of Solar Photovoltaic Systems) or equivalent. You must also be registered with a Competent Person Scheme for Part P notification, carry adequate public liability insurance, and meet the MCS quality management requirements, including documented procedures for system design, installation, commissioning, and handover.

Without MCS certification, the homeowner cannot register the installation for Smart Export Guarantee payments. This is a significant financial consideration — over a 25-year system lifetime, SEG payments can amount to several thousand pounds. MCS certification also provides consumer protection through the MCS Consumer Code.

Any electricity-generating installation connected to the public distribution network must comply with the relevant Engineering Recommendation published by the Energy Networks Association (ENA). For domestic solar PV, this means either G98 or G99, depending on the rated output of the system.

For three-phase installations, the G98 limit is approximately 11.04 kW (3.68 kW per phase). Systems above this require a G99 application regardless of the number of phases.

Installing a solar PV system involves adding new electrical circuits to the property, which is notifiable work under Part P of the Building Regulations. The work must be either self-certified through a Competent Person Scheme (such as NICEIC, NAPIT, or ELECSA) or notified to the local authority building control department before work commences.

Most MCS-certified installers are registered with a Competent Person Scheme, allowing them to self-certify the electrical work. A full Electrical Installation Certificate (EIC) is required for the new circuits — both the DC side (panels to inverter) and the AC side (inverter to consumer unit). A Minor Works Certificate is not appropriate because the work involves new circuits.

In addition to the electrical notification, the structural aspects of the installation may require consideration under the Building Regulations. In most cases, solar PV installations on existing domestic roofs are permitted development and do not require planning permission, provided the panels do not protrude more than 200mm from the roof surface and do not extend above the highest part of the roof. However, listed buildings, conservation areas, and certain other designations may require planning consent.

The earthing arrangement of the property is a critical consideration for solar PV installations. The majority of UK domestic properties have a TN-C-S (PME) earthing system, which creates specific safety considerations for PV arrays.

On a PME supply, the combined neutral-earth (PEN) conductor means that if an open PEN fault occurs, dangerous voltages can appear on the PME earth terminal. Because the PV array frame is typically mounted on the roof and connected via metallic mounting rails, any fault on the PME earth could energise the entire array frame structure — creating a hazard for anyone on the roof or in contact with the array.

For properties with a TN-S earthing system (earth provided by the cable sheath), the open PEN risk does not apply, and the array frame can be earthed to the main earthing terminal in the normal way. For properties with an existing TT earthing system, the earth electrode arrangements must be checked for adequacy.

Always verify the earthing arrangement by inspecting the supply and measuring Ze before designing the PV installation earthing scheme.

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The inverter converts DC electricity from the PV panels into AC electricity compatible with the household supply and the grid. There are two main types of inverter used in domestic installations, each with distinct advantages and implications for the electrical design.

A third option is power optimisers combined with a string inverter. Optimisers are fitted to each panel (like microinverters) but handle only DC-DC conversion and panel-level optimisation. The DC output still feeds into a central string inverter for DC-AC conversion. This provides many of the benefits of microinverters with a central inverter for easier maintenance and monitoring.

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Battery storage systems allow homeowners to store surplus solar electricity generated during the day for use in the evening and at night. A typical domestic battery stores 5-13 kWh of energy and costs £2,500-£6,000 installed. The addition of battery storage significantly increases the self-consumption ratio — the proportion of generated electricity used on site rather than exported — from typically 30-50% (without a battery) to 70-90% (with a battery).

For electricians, battery storage adds complexity to the installation. The battery system connects between the inverter and the consumer unit (AC-coupled) or between the PV array and the inverter (DC-coupled). Hybrid inverters that handle both PV input and battery charging/discharging are increasingly popular and simplify the wiring.

BS 7671:2018+A4:2026 Section 530 is particularly relevant to battery storage installations. Because a battery can supply fault current back through the consumer unit (bidirectional current flow), the protective devices must be suitable for operation in both directions. Standard unidirectional MCBs and RCBOs may not clear faults correctly when current flows in the reverse direction. Always check with the device manufacturer and the battery system designer that the protective devices are rated for bidirectional fault current.

Battery storage installations are notifiable under Part P and require appropriate certification. The consumer unit regulations apply in full, including the Amendment 4 requirements for bidirectional devices.

The Smart Export Guarantee (SEG) replaced the Feed-in Tariff (FiT) in January 2020 as the mechanism for paying domestic generators for electricity exported to the grid. Under the SEG, licensed electricity suppliers with more than 150,000 customers must offer at least one SEG tariff that pays a positive rate for exported electricity.

SEG tariff rates vary between suppliers and change regularly, but as of 2026, typical rates range from 4p to 15p per kWh exported, depending on the supplier and the tariff structure. Some suppliers offer fixed rates, while others offer variable rates that track wholesale electricity prices — these can be significantly higher during peak demand periods.

To register for the SEG, the installation must be MCS-certified and have a generation capacity up to 5 MW (for solar PV, practically all domestic installations qualify). A smart meter or export meter is required to measure the electricity exported. The homeowner applies to their chosen electricity supplier for a SEG tariff — they do not have to use the same supplier for their import tariff.

For a typical 4 kW domestic system generating approximately 3,400-3,800 kWh per year and exporting approximately 50% (1,700-1,900 kWh), the annual SEG income at current rates is approximately £100-£200. Over a 25-year system lifetime, this amounts to £2,500-£5,000 — a meaningful contribution to the payback calculation.

A domestic solar PV installation follows a structured process from the initial site survey through to commissioning and handover. Each stage involves specific technical considerations and documentation requirements.

Commissioning involves testing both the DC and AC sides of the installation. DC tests include open-circuit voltage (Voc) and short-circuit current (Isc) for each string, insulation resistance, earth continuity, and polarity. AC tests follow the standard BS 7671 requirements — earth fault loop impedance, prospective fault current, RCD operating times, insulation resistance, and continuity.

A domestic solar PV installation requires several pieces of documentation to be fully compliant:

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The total cost of a domestic solar PV installation depends on the system size, equipment specification, roof complexity, and the installer's pricing. As of 2026, typical costs for a standard domestic installation are:

The payback period depends on electricity prices, self-consumption ratio, and SEG income. At current UK electricity prices (approximately 24-28p per kWh), a typical 4 kW system saves the homeowner £500-£800 per year through reduced electricity bills and SEG payments. This gives a payback period of approximately 6-10 years. With a system lifetime of 25-30 years, the total financial benefit over the system life is substantial.

Adding battery storage extends the payback period (due to the additional capital cost) but significantly increases the self-consumption ratio and therefore the annual savings. With an EV or heat pump, the case for battery storage becomes even stronger.

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