If you’re exploring solar panels for your home or business, one of the first questions you’ll want answered is how many kWh a solar panel generates. Understanding this measurement is key to estimating your potential savings and environmental benefits.
A kilowatt-hour (kWh) is the standard unit of energy used by electricity suppliers. It represents the amount of energy used when a 1,000-watt appliance runs for one hour. For solar panels, kWh tells you how much usable electricity your system will produce—power you can use in your property or sell back to the grid.
Typical Output of Common Solar Panel Sizes
Most solar panels installed in the UK today are rated between 350W and 430W. Actual output in kWh depends on wattage, sunlight hours, and environmental factors.
For example, a 400W (0.4kW) solar panel in ideal UK summer conditions, with about four hours of strong sunlight per day, can generate:
- Daily: 0.4 kW × 4 hours = 1.6 kWh per day
- Monthly: 1.6 kWh × 30 days = 48 kWh per month
- Annually: 1.6 kWh × 365 days = 584 kWh per year
These numbers are averages. In winter, daily output may fall to 0.5–1 kWh per panel, while in the height of summer, you might see more than 2 kWh on a clear day. The actual amount you generate will depend on your location, roof angle, and whether your panels are ever shaded.
UK Averages vs. Ideal Conditions
A well-sited 400W panel in the UK typically produces between 350 and 600 kWh per year. The average solar panel output per day in the UK is 1–1.5 kWh, with higher yields in the South and slightly lower in the North.
For example:
- South England: Up to 1,100 kWh per kW installed annually.
- North Scotland: Around 850–900 kWh per kW installed annually.
These figures are based on real-world installations. For a typical UK home with a 4kW system (about 10–12 panels), annual generation could reach 3,500–4,400 kWh.
What Affects Solar Panel kWh Output?
A solar panel’s output depends on more than just its rated wattage. Key factors include:
- Roof angle and orientation: South-facing roofs at a 30–40° pitch are ideal. East- or west-facing roofs, or those with a shallower or steeper angle, will see reduced output.
- Shading: Even partial shading from trees, chimneys, or neighbouring buildings can significantly reduce efficiency. Modern systems often use optimisers or microinverters to reduce losses, but the best results are always achieved with unshaded panels.
- Weather and location: Solar panels generate electricity even on cloudy days, but output is naturally lower than in full sun. Southern regions of the UK enjoy more sunlight hours and higher annual generation than the North.
- Panel age and maintenance: Solar panels degrade slowly (typically 0.5–1% per year). Regular cleaning and prompt servicing help maintain peak efficiency.
- System design and quality: High-quality panels and inverters, professional installation, and well-designed cabling all contribute to maximising your system’s kWh output.
Practical Examples: Savings and Environmental Impact
A typical UK household consumes around 2,900–3,500 kWh per year. A well-designed 4kW solar system can generate most or all of this, depending on your usage and whether you include battery storage.
With current energy prices, a 4kW system can save up to £700–£900 per year on electricity bills. If you export surplus energy, you could earn even more. Each kWh of solar energy replaces grid electricity, cutting carbon emissions. A 4kW system can reduce CO₂ output by 1–1.5 tonnes annually—the equivalent of planting 40–50 trees every year.
Typical Solar Panel Output Table
|
Panel Size |
Daily Output (kWh) |
Monthly Output (kWh) |
Annual Output (kWh) |
|
350W |
1.2–1.4 |
36–42 |
430–510 |
|
400W |
1.4–1.6 |
42–48 |
510–584 |
|
430W |
1.5–1.8 |
45–54 |
540–650 |
A bar chart visualising kWh output by panel size (UK average vs. ideal) is a great way to present this data.
Learn More
Discover how our bespoke solar panel solutions can help you maximise your energy savings by visiting our solar installation page.
FAQ: Solar Panel Output and Performance
On average, a 400W solar panel generates between 1 and 1.6 kWh per day in typical UK conditions.
A 400W panel typically produces 350–600 kWh per year, depending on factors like roof angle, shading, and climate.
Roof orientation and pitch, shading, weather, panel age, and maintenance are the main factors. High-quality installation and regular cleaning also help.
Yes—solar panels work in diffuse light, so they continue generating electricity even on overcast days, though at lower output.
A south-facing roof with minimal shading and a pitch of 30–40° is ideal, but east or west-facing roofs can still be viable. Our team offers free site assessments.
A typical UK household can save up to 80% on electricity bills and may earn income by exporting surplus energy to the grid.
Contact Stratford Energy Solutions for a free, no-obligation quote tailored to your home or business.
Ready to Start Your Solar Journey?
Understanding how many kWh a solar panel generates empowers you to make informed decisions about your energy future. By considering panel size, your property’s specifics, and local conditions, you can accurately estimate your solar potential. If you’re ready to reduce your bills and carbon footprint, request a free quote or schedule a consultation with Stratford Energy Solutions. Our experts are here to help you every step of the way.
For more detailed UK solar statistics, visit the UK government’s solar PV deployment data.