Solar panel installation for houses on the Yorkshire coast.

Is my house suitable for solar panels?

Most houses with a roof that doesn't face north can take panels. A south-facing roof collects the most over a day, and east or west roofs still produce useful power, more of it in the morning on one and in the afternoon on the other.

Shade can matter more than direction. A chimney stack or a neighbour's tree can shade part of a roof for much of a winter's day, so notice where the shadows fall when the sun is low.

The roof covering matters because panels stay up for many years. If the tiles or the felt are near the end of their life, re-roofing first costs less than lifting an array off to do it later.

The structure has to carry the weight too. Building regulations normally apply to fixing panels to a roof, and its ability to take the load has to be checked, with strengthening where it falls short.

Bungalows and flat roofs can take panels as well. On a flat roof they sit on frames, and permitted development limits how high above the roof they can stand.

If the house is listed or sits in a conservation area, planning comes into it, and the council is the place to check before anyone climbs a ladder.

Solar panels with or without a battery

Panels on their own suit a household where someone is home in the day, running the washing machine or working from a spare room while the roof is generating. Without a battery, whatever the house can't use goes out through the meter as it's made.

A battery carries the daytime surplus into the evening, when most households use the most power. It adds to the cost at the start, and adding a battery later is usually possible if the first system is planned with room for one.

The fire-safety specification for home batteries keeps a battery out of bedrooms and lofts, so it usually ends up in a garage or on an outside wall.

What the wiring needs before panels go on

A solar system is a second source of power feeding the house, and BS 7671 treats it that way. The consumer unit needs room for the new circuit, and the devices protecting that circuit have to cope with power arriving from the panels as well as from the grid.

That second point catches older boards. An amendment to BS 7671 added a rule that where power can flow in both directions, only protective devices made for two-way flow may be used. A one-way RCBO fed from the wrong side can be damaged and stop protecting the circuit.

So if there's no spare way on the board, or its devices are marked for one direction only, the first job may be changing the consumer unit.

Some inverters also call for a particular type of RCD in front of them, and the manufacturer's instructions decide which.

The earthing and bonding get checked as well. A new source of supply relies on them like every other circuit in the house, and on an installation that hasn't been looked at for years they may need bringing up to date.

What happens when the panels go in

Scaffolding and the roof work come first, and the electrical side follows. Cable runs down from the array to the inverter, and the inverter feeds the consumer unit through a dedicated circuit.

There are switches on both sides of the inverter, so it can be isolated from the panels and from the mains for maintenance. Even with the mains side off, the cabling from the panels is live whenever daylight reaches them.

Under Part P of England's Building Regulations, fitting a new circuit counts as notifiable work. The finished work is tested against BS 7671 and certified before handover. Labels at the meter and at the consumer unit then warn anyone who opens the board later that the panels are a second supply to switch off.

What moves the cost of solar panels

The size of the system and whether a battery goes in decide most of the price. Access comes after that, since a tall gable or a conservatory in the way means more scaffolding.

Any electrical work the house needs first, such as a new consumer unit or better earthing, carries its own price, as does a car charger.

Plug-in solar kits

Small plug-in solar kits are now allowed in Great Britain. They're panels with a built-in inverter that plug into an ordinary socket, and each kit has to meet the government's product specification for plug-in solar devices.

In England they're covered by permitted development too, with limits on how far they stand off a wall and a ban on fixing them to timber cladding or a wooden balcony.

A kit like that is a small thing next to a roof system, but it still feeds power back through a socket. The socket and the circuit behind it need to be in good order, and in an older house that's worth having checked first.