Panel installation and wiring

Solar Panels for Beginners: How They Work and What to Expect in the UK

Solar panels turn daylight into electricity by driving electrons through a circuit. Understanding the basic components, how to size a system, and the legal difference between a plug-in kit and a full rooftop install takes about ten minutes and will save you a lot of confusion when comparing quotes.

Video: “Solar panels for beginners in the UK”, a UK solar advice channel.

1. How a solar panel generates electricity

A solar panel is made of photovoltaic (PV) cells, most commonly silicon. When photons from sunlight strike a PV cell, they knock electrons loose and set them moving through a circuit. That flow of electrons is direct current (DC). A panel is a group of cells wired together; an array is a group of panels.

The DC output of a panel varies with light intensity. On a clear summer day facing south, a 400 W panel might produce close to its rated output around solar noon. On an overcast winter afternoon in Kent, the same panel might produce 40 to 60 W. Over a full year, a south-facing 400 W panel in the UK typically generates around 340 to 380 kWh, depending on location and shading.

The DC output from the panels feeds into an inverter, which converts it to 230 V AC at 50 Hz: standard UK mains voltage. That AC output is then used in your home, and any surplus is either stored in a battery or exported to the grid.

2. What the main system components are

A complete grid-connected rooftop solar system has four essential parts:

• Panels: usually monocrystalline silicon today, rated at 400 W to 450 W per panel at standard test conditions. Monocrystalline panels are more efficient per square metre than older polycrystalline designs and are now the standard choice for UK rooftop installs.
• Inverter: converts DC from the panels to AC for your home. String inverters handle the whole array as a single input. Microinverters (one per panel) or DC optimisers allow panel-level monitoring and reduce the impact of shading on one panel dragging down the whole string.
• Mounting structure: aluminium rails and brackets fixed to the roof rafters. The panels attach to the rails. Penetrations through the roof are sealed, and a flashing kit is used around each bracket on a tiled roof to prevent water ingress.
• AC wiring and consumer unit connection: the inverter connects to a dedicated circuit breaker in your consumer unit. A generation meter is normally fitted to record total output for SEG payments.

A battery storage system is a separate component. It connects either on the DC side (between the panels and inverter, in a hybrid inverter setup) or on the AC side (after the inverter, as an AC-coupled battery). Adding a battery lets you store surplus midday generation and use it in the evening instead of drawing from the grid.

3. How to size a system for your home

Start with your annual electricity consumption, which you can find on your energy bills or in your smart meter app. A typical UK household uses around 3,500 kWh per year, but homes with an EV or a heat pump may use 6,000 to 10,000 kWh or more.

A rough rule: for every 1 kW of south-facing solar installed in East Kent, you can expect around 850 to 950 kWh of generation per year. A 4 kW system therefore generates roughly 3,400 to 3,800 kWh per year in good conditions, which is close to matching a typical household's annual use. In practice, much of that generation happens during the day when you may be out, so a battery improves self-consumption significantly.

East- and west-facing roofs produce around 15 to 20 percent less per year than south-facing, but they generate at slightly different times of day, which can be useful for spreading self-consumption across the morning and evening peaks. North-facing roofs are generally not viable for UK solar.

Your installer will produce a shading analysis (often using tools such as Google Sunroof data or a dedicated solar design tool) to account for chimneys, trees, and neighbouring buildings. Even partial shade on one panel can affect the whole string unless you have microinverters or DC optimisers fitted.

4. Plug-in kits versus a full MCS-certified install

A plug-in solar kit (one or two panels, a microinverter, and a cable that plugs into a standard socket) is a DIY product. The system offsets a portion of your daytime electricity use by injecting a small amount of AC into your home's circuits. It does not export to the grid or connect to your consumer unit. Under the UK rules that came into force on 27 August 2026, plug-in kits up to the limits set by the ENA register are legal and require no DNO notification. The trade-off is that the savings are modest: a single-panel plug-in kit might offset 300 to 400 kWh per year, saving roughly £75 to £100 at current rates.

A full rooftop installation exports surplus to the grid and earns export payments under the Smart Export Guarantee (SEG). SEG export rates from major energy suppliers currently range from around 3p to 15p per kWh. A 4 kW system exporting perhaps 1,000 to 1,500 kWh per year earns an additional £30 to £225 on top of the self-consumption savings. The total savings from a 4 kW system with a battery can be £800 to £1,200 per year at current electricity prices, giving a payback period of four to seven years depending on costs and tariff.

The full install must be carried out by an MCS-certified contractor. The DNO must be notified (G98 for systems up to 3.68 kW single-phase without battery export, G99 for everything larger or with battery export), and the installation must follow BS 7671. Your installer handles the DNO notification and MCS registration, which is what qualifies the system for SEG and the 0% VAT rate (currently in place until 31 March 2027, after which it reverts to 5%).

Frequently Asked Questions

How many solar panels do I need for a typical UK home?

A typical UK household using around 3,500 kWh per year and with a reasonably south-facing roof would usually start with a 3 to 4 kW system, which is roughly 7 to 10 panels at 400 W each. Homes with an EV or heat pump, or with higher electricity usage, often benefit from a 5 to 6 kW system or larger. The right size also depends on how much of your roof is available and unshaded, and whether you want to export surplus or just reduce daytime import.

Can I install solar panels myself in the UK?

A plug-in solar kit (under roughly 800 W, not connected to the main consumer unit) can be fitted by a competent DIYer on a fence, balcony, or garden structure and plugged into a standard socket. A full rooftop system that connects to your consumer unit or exports to the grid is a different matter: it must be designed and installed by an MCS-certified contractor, the DNO must be notified before the system is energised (G98 for smaller installs, G99 for larger or battery export), and the installation must follow the relevant British Standards. Working inside the consumer unit or on roof-tied DC strings always needs a qualified person.

Do solar panels work on cloudy days in the UK?

Yes, though they produce less. Solar panels generate electricity from daylight, not just direct sunshine, so they continue to produce on overcast days, just at a reduced rate, perhaps 10 to 25 percent of their rated output. The UK's annual solar resource is lower than southern Europe but is enough to make solar commercially viable, particularly when combined with a battery that captures daytime surplus for evening use. East Kent has above-average UK sunshine hours, which improves the case further.

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