Hi all — I'm setting up a small off-grid solar system for a cabin (lights, a small fridge, phone/laptop charging and a water pump) and I've been working through the sizing properly rather than guessing. Thought I'd share the method that's worked for me, in case it's useful to anyone here doing the same.

1. List your loads first
Write down everything you'll run, its wattage, and how many hours a day it runs. A 60 W fridge running 8 hours a day is 480 Wh; a 10 W LED for 5 hours is 50 Wh. Add them all up to get your daily watt-hours — that's the number everything else hangs on.

2. Size the battery bank
Take your daily watt-hours and divide by the battery voltage to get amp-hours, then roughly double it — you don't want to drain lead-acid below 50%, and even lithium lasts longer if you keep a reserve. Three cloudy days of autonomy is a sensible target for most of us.

3. Size the panels
Divide daily watt-hours by your average peak sun hours (4–5 in most of the US), then add about 25% for losses in the charge controller, wiring and inverter. So a 1,000 Wh/day load needs roughly 250–300 W of panels.

4. Match the charge controller and inverter
The controller must handle the panels' total short-circuit current, and the inverter should cover your biggest simultaneous load with some headroom — a 1,000 W inverter for a 700 W peak load, for example. Pure sine wave is worth it for anything with a motor or compressor.

5. Keep an eye on the system
A cheap battery monitor pays for itself — watching the state of charge daily teaches you more about your setup than any spreadsheet will.

I put together a free step-by-step guide with worked examples and a sizing calculator here: https://voltsolarguide.blog — it covers panel, battery and inverter sizing for off-grid homes.

Happy to compare notes — what size systems are others here running, and what would you change if you started again?