Off-Grid Calculators

Five calculators. Each one answers a single question, shows the arithmetic that produced the answer, and returns the result on screen immediately.

Three things none of them do, stated plainly because the category norm is otherwise. They do not ask for an email address before showing a result. They do not recommend products, name vendors or carry affiliate links. And they do not clamp, round down or soften an output to make it look more achievable — if your appliance list produces an uncomfortable number, the uncomfortable number is the answer, and softening it would only move the disappointment to the point at which you have already bought the hardware.

All five accept your own figures throughout and default to conservative assumptions rather than optimistic ones — shoulder-season sun hours rather than midsummer, real usable depth of discharge rather than nameplate capacity, and derate factors that account for temperature, soiling, tilt and wiring loss. A calculator that returns the nameplate figure is telling you that a 400W array delivers 400 watts, which it does not, on any day, anywhere.

Every result includes a show your working panel containing the full calculation populated with your own figures. This audience checks arithmetic. A tool that will not show its working is a lead magnet with a form on it.

The five

Off-grid load calculator How many watt-hours a day does this build actually use, and what battery bank and array does that imply? Start here — every other sizing question on the site depends on this number. Preloaded appliance library with realistic duty cycles already folded in.

Solar array and battery bank sizer How much array and how much storage do I need at my location, in my worst season? Takes daily consumption and location-specific sun hours, and runs a shoulder-season stress case rather than a midsummer best case.

Inverter surge sizing tool What size inverter do I need so it stops tripping? Continuous rating and surge rating are separate specifications and the second one is what fails. Accounts for the largest motor load and whether a soft start is fitted.

DC wire gauge and voltage drop calculator What gauge cable does this run need, and how much am I losing in it? Minimum AWG for your amperage and run length, the actual voltage drop at that gauge, and the next size up.

Five-year cost of ownership model What will this rig actually cost me, and what does that work out to per night? Purchase, finance, insurance, storage, fuel, maintenance and depreciation over five years — plus cost per night actually used, which is the figure nobody publishes and everybody wants.

How to use them together

The load calculator produces the number. The solar sizer turns it into hardware for your location and season. The surge tool sizes the inverter that number implies. The wire gauge calculator sizes the cable that inverter implies. The cost of ownership model tells you whether the whole proposition was sensible in the first place.

If you want the method rather than the tool, how many watts you actually need off-grid sets out the load-calculation process by hand.

One thing worth knowing before you build to any of these outputs: a substantial owner-installed electrical system changes your insurance position, and standard policies frequently do not cover what they are assumed to cover. Insuring a custom or converted vehicle explains where the gap sits.

Back to all sections.