Peak Power & Main Fuse Calculator

How to use this calculator

1. Enter your peak simultaneous power in kW — the largest load you expect at once (heating + EV + oven + sauna…).
2. Choose the supply: 1-phase 230 V or 3-phase 400 V.
3. Click Calculate for the current, the recommended main fuse and the capacity-tariff step.

How peak power, current and fuse relate

Current follows from the power and the supply; the main fuse is the next standard rating above the peak current:

Standard fuse ratings are 16, 20, 25, 32, 40, 50, 63, 80, 100 A. A capacity-based grid tariff (Norway since 2022, and parts of Sweden) bills the highest hourly power in the month, grouped into steps such as 0–2, 2–5, 5–10 and 10–15 kW.

Peak power, current and fuse

Reducing simultaneous use (load shifting) lowers both the fuse size needed and the capacity-tariff step.

Frequently asked questions

What size main fuse do I need?

Divide your peak power by the voltage (230 V single-phase, or √3 × 400 V three-phase) to get the current, then pick the next standard fuse above it — 16, 20, 25, 32, 40, 50 or 63 A.

What is a capacity (effekt) tariff?

A grid-rental model that charges for the highest hourly power you draw in a month, grouped into steps (e.g. 0–2, 2–5, 5–10 kW). It rewards spreading large loads out over time rather than running them together.

How do I lower my peak power?

Avoid running big loads at the same time — stagger EV charging, the sauna, the oven and water heating. Many EV chargers and heaters offer scheduling to shift load to off-peak hours.