Solar and Off-Grid Calculators
From a balcony panel to a full off-grid cabin or campervan: see what solar would make and save, size the batteries, panels and inverter, and choose cables that won't overheat.
Four free tools. No sign-up, nothing stored about you, and every result shows how it was worked out.
Solar & Off-Grid
The tools
Off-Grid Planner
Size the battery, solar panels and inverter for a cabin, van or boat.
Plug-in Solar Payback
See what a balcony solar kit would save and how many years it takes to pay back.
Solar Panel Calculator
See what solar panels on your roof would make and save, and how many years they take to pay back.
Cable Size Calculator
Work out the cable size and fuse for a 12 V, 24 V or 48 V circuit in a van, boat or off-grid system.
Which tool do I need?
Find the right tool
- To see what solar panels on your roof would make, save and pay back, use the Solar Panel Calculator.
- To check whether a plug-in (balcony) solar kit is worth it, use the Plug-in Solar Payback.
- To size the batteries, panels and inverter for an off-grid system, use the Off-Grid Planner.
- To choose the cable size and fuse for a 12, 24 or 48 V circuit, use the Cable Size Calculator.
Good to know
Before you start
Use what you use yourself
Solar pays back fastest on power you use as it's made. Power sent to the grid usually earns much less than you pay to buy it.
Plan for winter
Panels make three to five times less in December than in June in most of Europe. Off-grid systems need sizing for the dark months, not the average.
Low voltage, thick cable
At 12 V the current is high, so cable losses and heat add up fast. Keep runs short, size for 3% voltage drop or less, and fuse every circuit.
More tools
Other tool groups
Energy & Bills
Running costs, heating and radiators.
Damp & Air
Condensation, mould and dehumidifiers.
DIY & Materials
How much to buy for your next project.
Home & Living
Everyday jobs around the home.