The short answer
A 4kWp solar system — the most common size for a UK family home — typically costs around £6,000 to £9,000 fully installed, with 0% VAT applied. That generally buys around 10 panels, an inverter, mounting and full installation by an accredited installer. A 4kWp array in the UK generates roughly 3,400 to 4,000 kWh a year, depending on location, roof orientation and shading. Adding a battery raises the total by roughly £2,000–£5,000. The 4kWp size is popular because it fits the available roof space on a typical three-bedroom house and matches the electricity use of a normal family, giving a sensible balance between cost, generation and self-consumption.
The 4kWp system is the UK default for a reason: it suits a typical roof and a typical household. Here is what it costs and what you get back.
4kWp system at a glance
- Typical installed cost~£6,000–£9,000
- Number of panels~10
- Annual generation~3,400–4,000 kWh
- With a battery+£2,000–£5,000
- Suited toTypical 3-bed family home
What a 4kW system costs and includes
A 4kWp installation is a complete package, not just the panels. The headline price typically covers everything needed to get the system generating. The table breaks down what is included and the rough cost range.
| Element | What it is | Notes |
|---|---|---|
| ~10 panels (4kWp total) | The solar modules | Higher-efficiency panels cost more but generate more |
| Inverter | Converts DC to AC | String inverter standard; optimisers/microinverters cost more |
| Mounting + scaffolding | Roof fixings and access | Complex or tall roofs raise this |
| Installation + design | Survey, fitting, commissioning | By an MCS-certified installer |
| Total (typical) | Fully installed, 0% VAT | ~£6,000–£9,000 |
Indicative breakdown for guidance, 0% VAT applied. Sources: Energy Saving Trust; MCS. Final price depends on roof type, equipment and location.
How much it generates and saves
A 4kWp system in the UK generates roughly 3,400 to 4,000 kWh a year. The exact figure depends on:
- Location: the south of England receives more annual sunlight than the north of Scotland, so generation is higher.
- Orientation: a south-facing roof produces the most; east or west faces produce less but spread generation across the day.
- Pitch and shading: roof angle and any shade from trees, chimneys or neighbouring buildings affect output.
The financial benefit comes from two streams: the money you save by using your own generation instead of buying electricity, and Smart Export Guarantee income for the surplus you export. Because self-consumed power is worth the full retail price, a household that uses a good share of its generation during daylight hours gets the most value. For a typical home this combination usually puts payback in the region of 7 to 12 years, after which the system keeps saving for the rest of its 25-year-plus life.
The cost with a battery added
Many homeowners pair a 4kWp system with a home battery so they can store daytime surplus for use in the evening. This raises the upfront cost but increases the share of generation used at home:
- Battery cost: a home battery typically adds £2,000–£5,000 depending on usable capacity, taking a 4kWp-plus-storage system to roughly £8,000–£14,000 in total.
- Why people add one: a 4kWp array often generates more than the household uses during the day, especially when no one is home. A battery captures that surplus instead of exporting it cheaply, so more of it offsets evening usage at the full retail price.
- Whether it pays: the battery's payback depends on how much surplus you would otherwise export, your evening usage and your tariffs. It is worth checking the numbers for your household rather than assuming storage always pays.
For a home that is empty during the day, a battery often makes a 4kWp system noticeably more useful; for a home occupied and using power through the day, the panels alone may already self-consume well.
Frequently asked questions
How many panels are in a 4kW system?
A 4kWp system is typically made up of around 10 panels, though the exact number depends on the wattage of each panel. Higher-output panels mean fewer are needed to reach 4kWp, while standard panels mean slightly more. The installer sizes the array to your roof space and the 4kWp target.
How much electricity does a 4kW system generate?
In the UK, a 4kWp system generates roughly 3,400 to 4,000 kWh a year. The figure depends on location, roof orientation, pitch and shading — a south-facing roof in southern England sits toward the top of that range, while a shaded or north-leaning roof in the far north sits lower.
Is a 4kW system big enough for my home?
For a typical three-bedroom family home, a 4kWp system is usually a good match — it fits the available roof space and matches average electricity use. Homes with very high usage, an EV or a heat pump may benefit from a larger array or a battery. A survey can confirm the right size for your roof and consumption.
Sources & further reading
- Energy Saving Trust — solar panels
- MCS — find a certified installer
- GOV.UK — VAT on energy-saving materials
Figures on this page are typical UK ranges drawn from published sources and depend on your specific home. They are guidance, not a quotation or guaranteed saving.