Understanding how many solar panels you need is one of the most important parts of designing a solar system that works for your lifestyle. Whether you’re powering a home, a fridge, or just aiming to cut energy bills, the right number of panels depends on your daily usage, roof space, battery setup, and whether you plan to expand in future.
This guide answers key questions like how many panels are needed for different system sizes, what rules apply, and how much power you can expect to get from a typical UK solar setup.
How do I calculate how many solar panels I need?
Start with your daily electricity use
To work out how many solar panels you need, first check your electricity bill for your average daily or annual usage. A typical UK home uses around 3,500kWh a year. The more energy you use, the more panels you’ll need.
Panel output varies by size and efficiency
Most solar for home panels produce between 350–450W. Divide your annual usage by the total output per panel to get a rough count. For example, if you need 4,000kWh a year, and each panel gives you 400kWh/year, you’d need around 10 panels.
Consider your roof size and angle
Your roof space limits how many home solar arrays you can install. South-facing roofs perform best in the UK. Shaded areas, chimneys, or poor angles may reduce system efficiency — meaning more panels might be needed to reach your goal.
Use the 120% rule if planning for future growth
The solar 120% rule means your system can be sized to produce up to 120% of your past energy use. This is useful if you’re planning to add a battery, electric car, or heat pump later, and want to generate more now to prepare.
What is the 120% rule for solar panels?
It lets you oversize your system legally
In the UK, you can size your solar panel system up to 120% of your previous energy usage without extra planning hurdles. This flexibility helps futureproof your setup.
It supports smart energy systems
If you’re planning to install solar battery storage or connect an EV charger later, having a larger array now means you’ll already be generating enough power to support these add-ons.
| Benefit | Details |
|---|---|
| Legal Flexibility | In the UK, you can size your system up to 120% of previous energy usage without planning issues — ideal for future growth. |
| Smart System Ready | Larger systems support add-ons like EV chargers or solar batteries without needing later upgrades. |
| Faster Payback | Export more excess energy and benefit from Smart Export Guarantee (SEG) payments to reduce ROI time. |
| DNO Notification | If over 3.68kW per phase, DNO must be informed. New World Energy manages this process for all large installs. |
It can help reduce your payback time
Oversizing your system solar setup helps you export more energy to the grid, which you can sell through the Smart Export Guarantee (SEG). That reduces your ROI timeframe.
Check with your DNO if above 3.68kW per phase
If your system exceeds 3.68kW per phase, you’ll need to notify your DNO (Distribution Network Operator). New World Energy handles this process for all large-scale residential installs.
Is 6kW enough to run a house?
Is 6kW the Right Size for Your Home?
For many UK households, a 6kW solar panel system is the ideal choice. It provides enough power to cover daily needs like lighting, appliances, and electronics — and pairs well with battery storage for use after sunset.
Things to Consider:
- Typical Daily Use
A 6kW system suits the average home, but your actual energy needs may vary depending on when and how you use electricity. - Evening Energy Use
If your usage is higher in the evenings, adding a solar battery helps you store daytime energy for use later — improving efficiency and reducing reliance on the grid. - Household Size & Appliances
- Smaller homes or couples with light energy use might only need a 4kW system.
- Larger families or those with electric heating, multiple appliances, or solar water features may require more than 6kW to stay off-grid longer.
- Room to Grow
Starting with 6kW doesn’t limit you. You can gradually add:- Solar-powered garden lights
- Electric vehicle (EV) chargers
- Pool heaters or other high-draw devices
Your installer can plan for system expansion to support future upgrades.
Need Help Sizing Your Solar System?
Not sure how many solar panels you need? Whether you’re starting from scratch or upgrading an existing setup, New World Energy can help you plan a system that fits your home, roof space, and energy goals.
We provide expert guidance on system sizing, battery options, and export planning — including help with the 120% rule, SEG, and DNO applications. Our tailored installations ensure you get the most from your investment now and in the future.
Contact Us
New World Energy
Smart solar and battery storage installations across the UK.
Email: info@new-worldenergy.co.uk
Phone: 01865 600016
Website: www.new-worldenergy.co.uk
Need advice on how many panels are right for you? Get in touch with our team and we’ll help you build the perfect solar solution.
