The short answer is that most UK homes need between 8 and 16 solar panels to cover a large share of their annual electricity use. The exact number depends on how much electricity you use, how efficient your home is, and how suitable your roof is.
If you live in Horley, Reigate, Redhill, Crawley, or elsewhere in Surrey and West Sussex, the same basic rules apply as anywhere in the UK. What changes from house to house is usage, roof space, and expectations.
In this guide, we will cover:
- What “running your house” with solar really means
- How much electricity a typical UK home uses
- How much electricity one solar panel produces
- How to estimate the number of panels you need
- Roof space, direction and shading
- What if you want to add a battery?
- Can you run everything, including heating and EV charging?
- What happens in winter and at night?
- Installation, disruption and timescales
- Common mistakes and how to avoid them
What does “running your house” with solar actually mean?
For most people, it means generating enough electricity over a year to match what they use from the grid.
It does not usually mean being fully off-grid. In the UK, almost all homes with solar remain connected to the electricity network. You use your own solar power when it is available, and you import from the grid when it is not.
In summer, you may generate more than you use during the day. In winter, you will almost certainly import more. Over 12 months, though, your system can offset a large portion of your annual usage.
How much electricity does a typical UK home use?
The average UK household uses roughly 2,700 to 3,500 kilowatt hours per year. A kilowatt hour, often written as kWh, is a unit of electricity. It is what appears on your electricity bill.
Your usage may be higher if:
- You work from home most days
- You have an electric vehicle
- You use electric heating
- You run a small business from home
For example:
- A couple out at work all day in Redhill might use 2,500 to 3,000 kWh per year.
- A family of five in Crawley, with home working and an EV, might use 4,500 to 6,000 kWh or more.
Before sizing solar panels, you should check your last 12 months of electricity bills. That gives you a realistic starting point.
How much electricity does one solar panel produce in the UK?
Most modern panels installed today are rated between 400 and 450 watts. This is the panel’s peak output under ideal test conditions.
In the real world in Surrey or West Sussex, a single 420-watt panel might generate around 350 to 420 kWh per year, depending on roof direction and shading.
As a rough guide:
- 8 panels might produce 2,800 to 3,200 kWh per year
- 10 panels might produce 3,500 to 4,000 kWh per year
- 14 to 16 panels might produce 5,000 to 6,000 kWh per year
These are broad estimates. A proper design will look at your roof angle, direction and any shading from trees or nearby buildings.
How do you estimate how many panels you need?
Start with your annual electricity usage in kWh.
Then divide that by the expected annual output per panel.
For example:
If you use 3,600 kWh per year and one panel is expected to produce 380 kWh per year:
3,600 ÷ 380 = about 9.5 panels
So you would likely install 9 or 10 panels.
In practice, system size is also limited by:
- Available roof space
- Budget
- The maximum system size your local network will allow without extra approval
In some cases, your installer will discuss DNO approval. DNO stands for Distribution Network Operator. This is the company that manages the local electricity network. Larger systems sometimes need formal approval before installation.
JPEC Green Energy regularly handle this process for homeowners across Horley, Reigate, Redhill and Crawley, so you are not left navigating paperwork alone.
How much roof space do you need?
A typical modern panel is around 1.7 to 2 square metres.
As a very rough guide:
- 10 panels need around 17 to 20 square metres of clear roof space
- 14 panels need closer to 25 to 28 square metres
South-facing roofs produce the most, but east and west-facing roofs can still work very well. A split system across both sides often spreads generation more evenly through the day.
Things that reduce output include:
- Shading from chimneys, dormers or trees
- North-facing roofs
- Very shallow or very steep roof angles
A proper survey will include a shading assessment and generation estimate based on your exact address.
What if you want a battery as well?
A battery stores surplus solar electricity so you can use it later, usually in the evening.
Without a battery, most homes use 30 to 50 percent of their solar electricity directly. With a battery, this can often increase to 60 to 80 percent.
A battery does not usually mean you need more panels. Instead, it changes how much of your solar power you use yourself rather than exporting to the grid.
However:
- If your goal is to cover evening EV charging
- Or reduce peak-rate electricity imports
You may decide to slightly oversize your solar array.
Battery sizing depends on your evening and overnight usage. This is something that should be calculated properly rather than guessed.
Can solar panels run everything, including heating and EV charging?
They can contribute, but you need realistic expectations.
If you have:
- An electric vehicle
- An air source heat pump
- Electric cooking
- High daytime occupancy
Your electricity demand may be much higher than average.
For example, charging an EV can add 2,000 to 3,000 kWh per year. A heat pump may use 2,000 to 4,000 kWh per year depending on insulation and design.
In those cases, you may need 14 to 20 panels or more to cover a large share of usage. Roof space often becomes the limiting factor rather than panel efficiency.
In towns like Reigate or older parts of Horley, roof layout and conservation considerations can also affect what is practical.
A detailed design from an experienced installer such as JPEC Green Energy will help you understand what is achievable and where trade-offs sit.
What happens in winter and at night?
Solar panels only generate electricity during daylight.
They generate much less in winter than in summer. December and January output can be a fraction of June and July output.
That means:
- You will still rely on the grid, especially in winter.
- A battery will not fully solve winter shortfalls.
Solar in the UK works best when viewed as an annual offset, not a constant year-round supply.
This is one of the most common misunderstandings. Solar reduces your bills and carbon footprint, but it does not make you energy independent in most standard domestic setups.
What does installation involve?
For a typical house in Surrey or West Sussex, installation usually takes one to two days.
The process generally includes:
- Scaffolding set up
- Roof mounting system fixed to rafters
- Panels installed and wired
- An inverter fitted inside, often in the loft or garage
- Connection to your consumer unit
- Testing and commissioning
The inverter converts DC electricity from the panels into AC electricity that your home can use.
There will be some noise and access required, but most homeowners in Crawley or Redhill find disruption manageable. Power is usually off for a short period on the installation day.
After installation, your system must be registered with the DNO and you can apply for the Smart Export Guarantee. This is a scheme that pays you for exported electricity, although rates vary by supplier.
Common mistakes when sizing solar panels
The most frequent issues are not technical. They are expectation and planning problems.
Common mistakes include:
- Guessing annual usage instead of checking bills
- Forgetting about future changes like EVs
- Installing too few panels because of short-term budget thinking
- Expecting full off-grid independence
- Not checking roof condition before installation
If your roof needs replacing in a few years, it makes sense to deal with that first.
A clear conversation about your long-term plans is just as important as the technical design. This is where working with a local installer who understands housing stock in Horley, Reigate and the wider Surrey and West Sussex area can make a real difference.
So how many solar panels do you need?
For most UK homes:
- 8 to 10 panels suit lower-usage households
- 10 to 14 panels suit average families
- 14 to 20 panels may suit high-usage homes with EVs or heat pumps
The right answer depends on:
- Your annual kWh usage
- Your roof size and direction
- Whether you plan to add a battery
- Future changes in lifestyle or heating
There is no universal number. There is only the right design for your property.
JPEC Green Energy can help
If you are in Horley, Reigate, Redhill, Crawley, or elsewhere in Surrey and West Sussex, JPEC Green Energy can carry out a proper survey and design tailored to your home.
They can assess your roof, review your past electricity use, model realistic generation figures, explain battery options in plain English, and handle approvals and commissioning correctly. You will receive a clear quote based on your property, not a generic estimate.
To find out how many solar panels your home really needs, get in touch with JPEC Green Energy at 0800 955 2821 or renewables@jpecgroup.co.uk.
This guide is for general information only. Actual system size, performance and savings depend on your specific property, usage, tariffs and network conditions. Always confirm recommendations through a professional survey and design before proceeding.
