1. Introduction
Knowing the right number of solar panels for your home is crucial for maximising savings, energy efficiency, and return on investment. Install too few panels, and you won’t generate enough electricity to cover your needs; install too many, and you may overspend on an oversized system.
Several factors influence the number of solar panels required, including household energy consumption, your location’s sunlight hours, panel efficiency, and available roof space. This guide will walk you through each consideration to help you determine the optimal solar panel setup for your home.
2. Factors That Affect the Number of Solar Panels You Need
a) Household Energy Consumption
Your energy usage determines how much electricity your solar panels need to generate. To estimate your needs:
- Check your energy bill to find your annual electricity consumption in kilowatt-hours (kWh).
- Divide by 365 to get your daily kWh consumption.
For example, if your household uses 3,500 kWh per year, your daily usage is:
3,500kWh ÷ 365 = 9.6 kWh per day
Larger households or homes with energy-intensive appliances (like EV chargers or heat pumps) will have higher electricity needs.
b) Solar Panel Output
Solar panels come in different wattages, with 350W, 400W, and 450W solar panels being the most common. The higher the wattage, the fewer panels you need to generate the same energy. In the UK, a 400W solar panel produces about 1.6 kWh per day in optimal conditions. However, real-world conditions such as weather, shading, and seasonal variations can slightly reduce this output.
c) Location & Sunlight Hours
The whole of the UK receives an average of 4 peak sunlight hours per day across the year, but clearly this will vary significantly by season with summer months seeing much more sunlight than winter months. However, the overall average also varies by region:
- Southern England (e.g., London, Bristol): 4-4.5 hours
- Midlands & Wales (e.g., Birmingham, Cardiff): 3.5-4 hours
- Northern England & Scotland (e.g., Manchester, Glasgow): 3-3.5 hours
Solar panels only generate electricity when exposed to direct sunlight, meaning they won’t produce energy during the night and will generate less on cloudy days. This makes it essential to size your system correctly based on your location’s sunlight availability. A home in Scotland, for example, may require more solar panels than one in southern England to produce the same amount of energy.
d) Roof Space & Orientation
- Panel Size: A standard 400W panel measures about 1.7m x 1m.
- Roof Orientation: South-facing roofs generate the most electricity, while east- and west-facing panels produce around 80% of the maximum output. North-facing roofs generate significantly less, making them less ideal for solar panels, but they can still be viable with additional panels or high-efficiency models.
- Tilt Angle: A tilt of 30-40° is ideal for maximum efficiency.
- Measuring Roof Size: To estimate how many panels your roof can accommodate, measure the total roof area (length × width) and divide by the solar panel size (typically 1.7m² per panel). Keep in mind that obstructions like chimneys and skylights may reduce available space.
- Panel Size Variations: If space is limited, opting for higher-wattage solar panels (such as 450W) or more efficient monocrystalline panels can help maximise energy production.
3. Quick Calculation: Estimating Your Solar Panel Needs
A simple formula to estimate the number of panels required:
[Equation]9.6kWh ÷ 1.6 kWh =
Estimated Solar Panel Requirements Based on Home Size
| Home Size | Annual Usage (kWh) | Daily Usage (kWh) | Panels (400W) |
| Small (1-2 people) | 2,000 | 5.5 | 4 |
| Medium (3-4 people) | 3,500 | 9.6 | 6-7 |
| Large (5+ people) | 5,000 | 13.7 | 9 |
However, your location’s sunlight hours will influence this calculation. A home in northern England, receiving fewer peak sunlight hours, may require additional panels to generate the same energy as a home in the south. Roof orientation and space should also be factored in – north-facing roofs or limited space may require high-efficiency solar panels or additional units.
4. How Many Solar Panels to Cover 100% of Your Energy Usage?
While many homeowners aim to offset their full energy consumption, achieving 100% solar power isn’t always necessary.
- Solar panels generate different amounts of energy throughout the year, with more power produced in summer and less in winter.
- Many homeowners install a system that covers 70-90% of their needs, using grid electricity when solar production is lower.
- With the Smart Export Guarantee (SEG), excess electricity is exported back to the grid, providing additional savings.
For full coverage:
- Small homes: 4-6 panels
- Medium homes: 6-8 panels
- Large homes: 8-10+ panels
5. Battery Storage – Do You Need One?
Adding a solar battery allows you to store excess energy for later use, reducing reliance on the grid. If you use most of your electricity in the evening or at night, a solar battery can significantly improve self-sufficiency. However, if you consume most of your electricity during the day or can benefit from a high SEG rate, a battery may not be as cost-effective.
6. Grid Connection & Export Tariffs
With the Smart Export Guarantee (SEG), UK homeowners can sell surplus electricity back to the grid, earning between 3-15p per kWh, depending on the provider. The total gain depends on:
- Whether you have a solar battery: Storing energy reduces exports but maximises self-consumption.
- System size: A larger system generates more surplus energy, increasing SEG payments.
- Additional panels: Installing extra panels increases energy generation, allowing for higher SEG earnings.
7. Cost Considerations
| Home Size | System Size (kW) | Number of Panels | Estimated Cost (£) |
| Small (1-2 people) | 3-4 kW | 6-10 | £5,000-£7,000 |
| Medium (3-4 people) | 5-6 kW | 10-12 | £7,000-£9,000 |
| Large (5+ people) | 8+ kW | 14+ | £9,000+ |
These costs depend on factors like solar panel efficiency, installation complexity, and battery storage. For a more accurate quote, contact Cotswold Energy for a personalised assessment.
8. Conclusion & Next Steps
The number of solar panels you need depends on your energy usage, location, roof size, and budget. Most UK homes require 6-10 panels for substantial energy savings.
Next Steps:
✅ Use our calculation formula to estimate your needs.
✅ Consult Cotswold Energy for a free home assessment.
✅ Compare panel options to find the best fit for your needs.
Considering solar? Contact Cotswold Energy today for expert advice and tailored solutions.