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Boat Power Calculator

Calculate cable size, fuse size, battery bank, solar system and power consumption directly on your phone. Includes realistic daily consumption, peak load, solar sizing and battery sizing.

Need equipment for your setup? Visit Sejlstrøm for cables, fuse holders, batteries, chargers and solar products.
Sets sensible defaults and suggested standard loads.
Affects solar hours and margin.
Advanced system settings
Keep the default values unless you have unusual shading, year-round use, long cable runs or large startup currents.

Loads

Mark “Simultaneous?” for loads that can realistically run at the same time. This is used for peak load, inverter and cable sizing.
Item W Qty Hours/day Simultaneous? Wh/day

Tip

Add standard items, edit them if needed, and create your own custom rows freely.

Add loads and calculate to see total daily consumption.

Results overview

Max simultaneous incl. margin (W)
0
Consumption per day
0 Wh
0,00 kWh
Recommended solar (W)
0
Battery for 2 days without sun
0 Wh
0 Ah

Real-world note

This calculator uses margin and loss factors so the result is closer to real-life Danish conditions.

Cable size calculator

If you enter a fuse size here, the cable is sized from the highest value of load current and selected fuse.

Good to know

A larger fuse than the load current means the cable should usually be sized after the fuse value.

Fuse size calculator

Important

The fuse must protect the cable, not only the appliance.

Battery bank calculator

Assumption

Lithium is calculated with 90% usable capacity and AGM / lead-acid with 50%.

Solar calculator

Note

Real output depends on season, angle, shading and controller quality.

Summary

Fill in the calculators to generate a complete summary.

Request a quote

Fill in your details and send your calculation directly to Sejlstrøm.

Sejlstrøm helps boat owners with practical solutions for 12V / 24V electrical systems.

Calculations are indicative only and should always be checked against the actual installation, cable routing, temperature, load and applicable standards.

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