Overland power calculators
Seven tools for the arithmetic that decides whether a 12V build works. Battery bank sizing and solar output are the two people get wrong most expensively, so start there.
<!-- gift-guides-xlink -->Which calculator do you need first?
Work in this order and each tool feeds the next. Start with the power consumption calculator to turn a list of appliances into a daily amp-hour figure, because every other number on this site depends on it. Feed that into the battery bank calculator to size the bank, then into the solar array calculator to see what a roof can put back each day.
Once the system is sized, the wire gauge calculator and the inverter sizing calculator decide the parts that keep it safe. Wire gauge is the one to take seriously: 12V at high current is a genuine fire risk, and the difference between a correct and an optimistic cable size is not academic.
Two tools cover the constraints people forget until the build is finished. The payload calculator checks the whole build against the sticker on your own door jamb, and the water capacity calculator turns days on the road into gallons and into the 8.34 lb per gallon that comes with them.
All calculators (7)
- Battery Bank Calculator: Size a 12V House Battery from a Load ListTurn a device load list into a required battery bank size in amp-hours, with usable depth of discharge by chemistry, inverter... Open →
- Inverter Sizing Calculator: Continuous Watts, Surge and DC CurrentSize a 12V inverter from the AC loads you actually run at once, with surge headroom for motor starts, the DC current on the battery... Open →
- Payload Weight Calculator: GVWR Headroom for an Overland BuildCheck a full overland build against your vehicle payload and roof load limits, with real component weights for batteries, solar... Open →
- Power Consumption Calculator: Daily Watt-Hours and Amp-HoursWork out what a single appliance costs you per day in watt-hours and amp-hours at 12V, including duty cycle and inverter losses... Open →
- Solar Array Calculator: Panel Watts to Daily Amp-HoursConvert solar panel watts and peak sun hours into the amp-hours that actually reach a 12V battery, with the real-world derate... Open →
- Water Capacity Calculator: Gallons, Days and PayloadWork out how much fresh water an overland trip needs, how long a given tank lasts, what the water weighs against your payload, and... Open →
- Wire Gauge Calculator: Ampacity and Voltage Drop for 12V RunsSize 12V and 24V DC cable correctly against both tests at once: ABYC E-11 ampacity with the engine space derate, and voltage drop... Open →
Electrical safety: a 12V system is low voltage but not low energy. Every circuit must be fused at the source of power, within a few inches of the battery terminal, at or below the ampacity of the smallest conductor it protects. Size cable for voltage drop as well as ampacity, and have any lithium installation inspected by a qualified installer before it carries load. Everything on this site is researched guidance, not an electrical certification.