The maths behind the numbers
The calculator gives you an answer. These explain how it got there, so you can check it, argue with it, and spot when an installer's quote does not add up.
How many solar panels do I actually need?
Work backwards from your bill to a panel count — and see why the answer changes by a factor of two between Oslo and Dubai.
Read the guide → · 9 minInvertersWhat size inverter do I need?
DC/AC ratio, deliberate clipping, surge current, and the difference between on-grid, hybrid and off-grid units.
Read the guide → · 8 minBatteriesHow to size a solar battery bank
Depth of discharge, C-rate, round-trip losses, and why a 10 kWh lead-acid bank is not a 10 kWh battery.
Read the guide → · 9 minPerformanceWhy your panels produce less than their rating
Every loss between the datasheet and your meter, quantified — heat, dust, wiring, shade and inverter.
Read the guide → · 8 minEconomicsNet metering or a battery?
Which one pays back faster, how to tell which regime you are in, and what happens when the rules change.
Read the guide → · 8 minThe full methodology
Every formula, constant and data source the calculator uses, written out in full so you can reproduce it yourself.
Read the method → ToolThe calculator
Panel count, inverter size, battery capacity and payback for your exact coordinates. Free, no sign-up, no sales call.
Size my system →