Solar Calculator – Solar Panel & Off‑Grid System Size Tool
Calculate your solar panel size, battery storage, and inverter requirements in minutes. Designed for UK conditions and real-world setups.
Solar Panel Calculator – How Many Panels Do You Need?
Most small off-grid systems need between 2–12 solar panels, depending on usage.
| System Size | Typical Panel Count |
|---|---|
| Small off‑grid setup | 2–4 panels |
| Garden office system | 4–6 panels |
| Small home system | 8–12 panels |
How the Solar Calculator Works
- Estimate your daily energy use (Wh)
Add up the appliances you want to run and how many hours you use them each day. - Convert energy into solar panel size
The calculator works out how much solar generation you’ll need based on typical UK sunlight hours. - Calculate battery storage
It estimates how much battery capacity you’ll need to store power for evenings or cloudy days. - Size your inverter correctly
The tool determines the inverter size needed to handle the total power draw of your appliances.
This gives you a balanced, real-world system size without overcomplicating things.
Ready to size your system?
Enter your appliances above to calculate your setup.
Example Solar Setups
Small Garden Office Solar Setup
A simple garden office usually runs only a few devices each day.
| Appliance | Watts | Hours | Wh/day |
| Laptop | 60W | 6 | 360 |
| LED lights | 10W | 4 | 40 |
Estimated system:
- ~400W solar panel capacity
- ~1kWh battery storage
In many cases, this is enough to power a basic workspace during the day.
Campervan Solar Setup
Campervans often require slightly larger battery storage because appliances may run overnight.
| Appliance | Watts | Hours |
| Fridge | 50W | 24 |
| Lights | 8W | 5 |
Estimated system:
- ~300W solar panels
- ~1.2kWh battery storage
Of course, real‑world systems vary depending on travel habits, weather conditions, and energy usage.
Frequently Asked Questions
The number of panels depends on your total daily energy usage. Small off‑grid systems may only require two to four panels, while larger systems require more.
Battery capacity should usually store one to two days of energy usage, allowing the system to run overnight or during cloudy weather.
Most systems require both a battery and an inverter. Solar panels alone cannot reliably power appliances when sunlight levels change.
Yes. The calculator uses conservative assumptions designed for typical UK sunlight levels.
Small cabins often require 300W–800W of solar panels with around 1–3kWh of battery storage, depending on appliance usage.