Is your home suitable for solar panels? A UK guide

Helpful video reference. We reference Artisan Electrics' "Don't get Solar PV until you've watched this video!" here for the practical questions it raises before committing to an installation. Artisan Electrics cover UK solar and electrical work from an installer's perspective, and the video is candid about the things salespeople do not always raise upfront.

1. Check your roof orientation

Stand in the garden and open the compass app on your phone. Point it at the centre of your roof slope. The direction it faces is the azimuth.

• South (150-210 degrees): optimal. Maximum generation over the year.
• South-east or south-west (120-150, 210-240 degrees): good. Typically 85-95% of south output. South-east generates more in the morning, south-west more in the afternoon - which you prefer depends on when you use most electricity.
• East or west (60-120, 240-300 degrees): viable but not ideal. Roughly 70-80% of south. More useful if you have a time-of-use tariff (charging a battery in the morning from east panels, for example).
• North-facing: not normally economically viable in the UK.

A hipped roof (four slopes meeting at a ridge) may give you usable area on south-east, south and south-west faces simultaneously. Your installer will model the combined output.

2. Check your roof pitch

Panels work best at 30-50 degrees from horizontal. This is common on UK semi-detached and terraced houses built from the 1930s onwards. Steeper or shallower pitches reduce output slightly but are still viable.

For flat roofs (garage tops, flat extensions, some modern builds), panels are mounted on tilted frames. This adds structural load considerations and wind loading, which your installer and possibly a structural engineer should assess. Flat panel installations that lie close to horizontal also accumulate more dirt and need more regular cleaning.

3. Assess shading carefully

This is the most commonly underestimated factor. In a standard string inverter setup, a shadow on a single cell can drag down the output of the entire string connected to that inverter. Optimisers or microinverters can mitigate this but they add cost.

Look for these shading sources at different times of day:

• Your own chimney stack (often casts a shadow across the roof in the morning or late afternoon)
• Dormer windows or roof extensions
• Satellite dish and its mast
• Trees, especially deciduous ones that will be in full leaf during summer peak generation months
• Neighbouring buildings - particularly relevant for terraced houses where a taller neighbour to the south blocks the low winter sun

Use the PVGIS tool (pvgis.ec.europa.eu), which is free and covers the UK, to model estimated generation for your specific roof orientation and pitch. It does not model local shading, so you still need to assess that yourself.

4. Check your roof condition

Solar panels are typically performance-guaranteed for 25 years. If your roof tiles or slates are already 15-20 years old and showing wear, it makes far more sense to re-tile before installation. Removing and reinstalling a panel array to get at the roof later typically adds £1,500-3,000 to the roofing cost.

Ask a roofer (not your solar installer) for an independent condition report. Things to flag:

• Cracked, slipped or missing tiles or slates
• Flashings around chimneys or valleys that are failing
• Any sign of felt deterioration or ponding on a flat section
• Ridge tiles that are not well-bedded

Also check the roof structure from the loft if accessible. The additional load of a solar array (roughly 15-20 kg per square metre) is within what most standard UK roofs can carry, but a surveyor should confirm this on older or non-standard properties.

5. Understand your electricity usage

Solar panels only save you money on units you would otherwise have bought from the grid. If you are out all day Monday to Friday, the panels generate most of their energy while the house is empty and you export it at the Smart Export Guarantee (SEG) rate, which is considerably lower than what you pay to import.

Look at your last 12 months of electricity bills and add up the total kWh consumed. In east Kent, an average family home uses 3,000-4,500 kWh per year. A 4 kWp system generates roughly 3,500-4,000 kWh per year here, so there is a reasonable match.

If you drive an electric vehicle or heat with a heat pump, your annual consumption may be double this, which makes solar considerably more attractive because there is more to self-consume.

6. Check your electrical supply type

Most UK homes have a single-phase supply (one live, one neutral, one earth). Some larger properties, newer homes and some rural ones have three-phase. You can usually tell by looking at the consumer unit: a single-phase board has a 100A main fuse; three-phase boards often have three groups of MCBs and a correspondingly larger main switch.

For solar purposes:

• Single-phase: one inverter, one AC connection point. Maximum G98 self-notification size is 3.68 kW single inverter output.
• Three-phase: the installer can balance panels across phases, which is more efficient for larger arrays.

Your consumer unit also needs at least one spare MCB way for the inverter connection. If the board is full, you will need a new consumer unit or a sub-board - your electrician can advise on the simplest route.

Finally: if you have an older analogue meter that is not bidirectional, your supplier will need to replace it (usually at no charge) before you can receive SEG export payments.

7. Understand the DNO notification requirement

Before your installer connects the inverter to the grid, they must notify your Distribution Network Operator (DNO). In Sandwich and most of east Kent, this is UK Power Networks.

• G98 (under 3.68 kW per phase): a simple self-notification. The installer submits a form, waits 28 days, and then installs. Your installer does this routinely.
• G99 (over 3.68 kW per phase): requires a full application and approval before installation. Approval can take 45-90 days and may involve design changes.

This is why many domestic installations are sized at exactly 3.68 kW: it keeps the process simple. If you want more capacity and do not want the delay, battery storage can bank the extra generation without pushing exported power over the threshold.

8. Check planning permission

Most domestic solar installations in England are permitted development and do not need planning permission, provided they:

• Are on a pitched or flat roof (not on a wall)
• Do not protrude more than 200mm from the roof plane
• Are not on a listed building
• Are not in a conservation area where the installation would be visible from a highway
• Do not exceed the highest part of the roof

If your house is listed, you need listed building consent as well as planning permission. Some conservation areas in east Kent, including parts of Sandwich itself, have stricter permitted development rules. Check with Canterbury City Council's planning department if you are unsure - it is free to ask and the alternative (installing without consent and being required to remove the panels) is expensive.

When to call us

Richard does not install solar panels but he does the electrical work that goes with them: consumer unit assessments, additional ways, inverter connections, EICR inspections ahead of installation, and any remedial work that an installer's survey flags. If you are getting quotes and an electrician's input would be useful, give us a call.