Panel sizes
Solar panel size calculator: panels, watts, kWp and roof space
Type the panels on your quote, a system size or the roof you have. You get the kWp, the roof space, the weight, a year's generation, the usual price and payback, and what a battery and an export rate change. For scale: a standard UK panel is about 1.76 m by 1.13 m and rated 430 to 460 W. Twelve of them make a 5.28 kWp system on 26.4–30 m² of roof and, going by 14,879 metered UK homes, make about 3,600–4,400 kWh a year.
Last updated 1 November 2026.
What does that quote add up to?
Type the panels as the quote lists them. You get the system size, the roof it needs, the weight, what homes with that much solar made in a year, and what it costs and pays back.
Know the panel's dimensions?
System size
5.28 kWp
12 panels at 440 W, direction not set. Panel size taken from a typical 440 W panel.
kWp is the system's peak output, and the number to compare quotes on. 12 panels is a normal size for a UK house, where most installs run 8 to 14.
Roof space
26.4–30 m²
24 m² of panel
Weight
250–300 kg
About 10.5–12.5 kg per m², well inside what a UK roof is built for
Generation
3,580–4,430 kWh
A year, direction not set
Annual saving
£415–£790
A year, no battery, give or take 20%
Install cost
£7,095–£11,070
Typical fitted price, no battery
Payback
12–18yrs
Before it pays for itself
How that adds up
- Used at home, about 31%
- 1,250 kWh
- Exported, the rest
- 2,340–3,190 kWh
- Bill savings
- £300–£375/yr
- Export income at 5–13p
- £115–£415/yr
- Together
- £415–£790/yr
The annual saving above is the middle figure, give or take 20%. This line adds the two parts at their low and high ends.
This array covers the home's own daytime use: past this point the extra power is exported, which earns less than it saves.
Battery size for this home
3.5–5 kWh
For a home using 2,500 kWh a year: the panels could fill more, but the home does not use it in the evenings. Common size: 5 kWh.
Take it further
See this system month by month in the savings calculator, then check your roof and get quotes from listed installers.
Generation is what 14,879 metered UK homes made in 2024. Metered figures: openclimatefix/uk_pv (Hugging Face, CC-BY-4.0), collected by Sheffield Solar. UK 2026 prices. Estimates to plan around, not a survey. How we measure.
Solar panel sizes and dimensions: how big is a panel?
Nearly every panel sold for UK homes is 1.13 m wide. The length sets the wattage: more cells, more watts, more roof. These are the formats you will see on quotes, typical of each size rather than any one brand's datasheet.
Older 60-cell panel
1.69 m × 1 m, 300–399 W
1.69 m², 18–21 kg. Domestic.
108 half-cell, shorter
1.722 m × 1.134 m, 400–430 W
1.95 m², 21–24 kg. Domestic.
108 half-cell, standard
1.762 m × 1.134 m, 431–465 W
2.00 m², 21–25 kg. Domestic.
120 half-cell
1.903 m × 1.134 m, 466–499 W
2.16 m², 23–27 kg. Domestic.
132 half-cell
2.094 m × 1.134 m, 500–539 W
2.37 m², 25–30 kg. Commercial format; unusual on a house.
144 half-cell
2.278 m × 1.134 m, 540–599 W
2.58 m², 27–32 kg. Commercial format; unusual on a house.
156 half-cell
2.465 m × 1.134 m, 600–650 W
2.80 m², 29–35 kg. Commercial format; unusual on a house.
How many solar panels is a 3 kW, 4 kW or 6 kW system?
Divide the system size by the panel wattage and round up. A "4 kW" quote at 440 W is nine or ten panels, and ten of them is really 4.4 kWp, which is why two quotes for the same size can show different panel counts and different prices. The roof figure is what that many panels occupy with gaps and edges allowed for.
| System | 400 W panels | 440 W panels | 500 W panels | Roof at 440 W |
|---|---|---|---|---|
| 3 kW | 7–8 panels | 6–7 panels | 6 panels | 15.4–17.5 m² |
| 4 kW | 10 panels | 9–10 panels | 8 panels | 22–25 m² |
| 5 kW | 12–13 panels | 11–12 panels | 10 panels | 26.4–30 m² |
| 6 kW | 15 panels | 13–14 panels | 12 panels | 30.8–35 m² |
Which size your home needs is a question about your bills, not your roof: our how many panels guide works it through.
How much roof space do solar panels need?
Each standard panel is just under 2 m² of glass, and an array takes 1.1 to 1.25 times its own outline once you allow for gaps, rails and a 0.3 m margin at the edges. So ten panels want 22–25 m² of clear roof, twelve want 26.4–30 m². A typical three-bed semi has 20–35 m² on its best face, which is why 8 to 14 panels is the normal domestic range. Give the calculator a width and height and it fits the grid for you, both ways round.
What size battery for a solar system?
Two numbers decide it. The first is how much electricity the home uses between late afternoon and the next morning, when the panels make nothing: for most homes that is 4–7 kWh, more with an EV or a heat pump. The second is how much the panels can put into it, roughly 1 to 2 kWh per kWp of array. A battery bigger than the smaller of those two sits part-empty most of the year. That is how 4 kWp on a 2,500 kWh home lands near 5 kWh and 6 kWp on a 4,500 kWh home nearer 10. The battery sizing guide has the detail.
What is an export tariff worth?
Whatever you do not use at home goes to the grid, and under the Smart Export Guarantee your supplier pays for it. Mainstream rates sit at 5–13p per kWh; a few pay 15–16p to their own import customers. For a 4 kWp home exporting 1,500–2,500 kWh a year, the gap between 5p and 15p is worth £150–£250. The calculator lets you set the rate on the offer in front of you and see what it changes, but a battery usually changes it more: it halves the export, so a high rate matters less. Named rates and their conditions are in the SEG tariff comparison.
The figures behind it
2026 assumptions.
Panel formats
7 module outlines, 300–650 W
The usual size for each wattage, not any one brand. Pick a wattage and we use its usual size; type the dimensions from your datasheet and we use those.
Weight
10.5–12.5 kg per m²
Glass-foil modules at the low end, glass-glass at the high end. A standard 1.76 m panel reads 21–25 kg on current datasheets.
Roof space
1.1–1.25 × the panel area
Allows for gaps, rails and a 0.3 m clear strip round the edge. Give a width and height and we lay out the actual rows instead.
Generation
677–838 kWh per kWp nationally
The typical half of 14,879 UK homes with metered solar in 2024, leaving out the best and the worst. Narrowed to your area and roof direction when you give them.
Battery demand
45–65% of daily use, ÷ 0.9
The share of a day's electricity used after the panels stop, sized up because you can only use about 90% of a battery's rated capacity. An EV adds 8 kWh a day, a heat pump 6.
Battery per kWp
1–2 kWh per kWp of panels
A battery much bigger than twice the array seldom fills outside summer. The suggestion is where this band and the demand band overlap.
Export rate
5–13p per kWh unless you set one
The mainstream Smart Export Guarantee band. Set your own rate, 0–30p, and it replaces the band for that run.
Electricity price
24–30p per kWh
Low end tracks the Ofgem price cap; high end covers non-direct-debit and regional spread.
Metered figures: openclimatefix/uk_pv (Hugging Face, CC-BY-4.0), collected by Sheffield Solar.
Know your panel count. Now check the roof.
Check your own roof.
Enter your property number and postcode today, and we'll read your roof from the sky to get a better understanding of whether or not your roof is suitable for solar panels. Free, takes minutes, and no account necessary.
Common questions
Panel sizes, answered.
How big is a standard solar panel in the UK?
A typical domestic panel today is about 1.76 m by 1.13 m, just under 2 m², and rated 430 to 460 W. The shorter 1.72 m format carries 400 to 430 W. Panels over 2 m long (500 W and up) are commercial formats and rarely go on houses. Weight is 21 to 25 kg for the standard size.
Is a 440 W panel better than a 400 W one?
Only in the sense that it makes about 10% more from the same footprint, since both are the same outline. Ten 440 W panels are 4.4 kWp; ten 400 W panels are 4.0 kWp. On a roof with room to spare, more lower-watt panels can beat fewer high-watt ones. On a tight roof the higher wattage wins. Compare quotes by total kWp and price, not by the panel rating alone.
How many solar panels is a 4 kW system?
10 panels at 400 W, 9–10 at 440 W or 8 at 500 W. Installers round to whole panels, so a "4 kW" quote is often 4.4 kWp. The calculator above shows the roof space each version needs.
Can my roof take the weight of solar panels?
Almost always. A twelve-panel array weighs around 250 to 300 kg including the modules, spread over 25 m² or more, which is roughly 10 to 12 kg per square metre. A UK pitched roof is designed for far more than that in snow and wind. The installer checks the rafters and fixings on the survey; it is a standard part of an MCS installation.
Should I get a 5 kWh or a 10 kWh battery?
Size it to what the home uses between late afternoon and morning, then check the panels can fill it. A home on 2,500 kWh a year with 4 kWp usually lands around 5 kWh; a family on 4,000 to 5,000 kWh with 6 kWp nearer 10 kWh. Bigger only pays if it fills and empties most days. The calculator shows both bands for your figures.
What is an export tariff worth with this many panels?
It depends on how much you export, which is most of the output for a home that is out by day with no battery. A 4 kWp system exporting 2,000 kWh earns about £100 a year at 5p and about £240 at 12p. The highest rates usually require the same supplier for your import electricity, so compare the whole bill, not the headline export rate.
