Inverters: pure sine, sizing, and when to skip one

Converting 12V battery power into normal 230V sockets.

An inverter turns your battery's DC into 230V AC. Three rules:

Buy pure sine wave, not modified sine. Modified sine inverters are cheaper but make laptop power supplies buzz, kill some electronics, and upset anything with a motor. Pure sine costs a little more (£50–100 for 300–500W; £150–250 for 1,000–2,000W) and runs everything cleanly.

**Size it to your biggest *simultaneous* load, plus 25% headroom.** Laptop + monitor + lights ≈ 110W → a 300W inverter is plenty. The moment a heater or kettle enters the picture you need 2,000–3,000W — and a battery bank that can deliver it.

Consider skipping it. Inverters waste 8–15% of everything passing through, plus a constant standby drain. USB-C laptop chargers, LED lighting and phone charging all exist in efficient 12V versions. A 12V-only shed is simpler, safer and cheaper.

From EcoPowerful — plain-English DIY solar & wind guidance for UK homes, with a free instant system plan builder. Guidance is general; 230V fixed wiring always needs a qualified electrician. Last updated 2026-06-13.