Free tools

PLANNING TOOL · NO ACCOUNT REQUIRED

Onboard electrical load planner.

Add common onboard appliances to estimate daily watt-hours, peak watts and baseline battery capacity.

Power in watts multiplied by hours gives energy in watt-hours. A 50 watt load running 8 hours uses 400 watt-hours. Add device energy for a daily budget; account separately for surge and simultaneous power.
Slide the drawing sideways to read the full plate.
Power is not energyPower in watts multiplied by hours gives energy in watt-hours. A 50 watt load running 8 hours uses 400 watt-hours. Add device energy for a daily budget; account separately for surge and simultaneous power.Reference: Existing calculator — electrical load planner

INTERACTIVE CALCULATOR

Adjust the inputs. Estimates update instantly; nothing is uploaded.

LoadRunning WHours/day

YOUR ESTIMATE

Enter measurements to see the calculation.
How it works

Daily energy = sum of (watts × hours). Simultaneous running watts are shown as a deliberately conservative sum of all entered running loads, not a measured demand profile.

Important limitation

This is not an inverter surge design. Motor startup currents, inverter losses, compressor duty cycle and power factor are not modeled; use manufacturer data for actual system sizing.

IF YOU WANT THE WHOLE STORY

The math is the beginning.

A quiet night at anchor, a microwave and a diesel generator are three different purchasing decisions masquerading as one.

Read the companion guide

PUT THE RESULT TO WORK

Put a real liner in the power budget

Gerbing lists 77 watts for its 12V Jacket Liner 2.0. At 12 volts that is about 6.4 amps before adding any other equipment. That concrete load is more useful than describing the garment as low-power. Your vehicle still needs enough documented accessory and charging capacity for the complete setup.

Read the buying guide →