You know the loads you want to run. SpecBuildr asks a short set of plain-English questions and turns them into a complete off-grid power specification — array, battery, inverter, and days of autonomy — sized for your site.
Off-grid sizing is where DIY builds go wrong: buy a mismatched pile of panels, batteries, and an inverter, and it browns out in winter or can't start the well pump.
The math ties loads, sun hours, autonomy, and voltage together — miss one and the whole system is under- or over-built. SpecBuildr asks about your loads and site in plain language and turns the answers into a balanced system spec you can hand to a distributor or installer.
A balanced system spec comes down to six things. Here's what each means in plain terms.
Location, sun hours, and mounting (roof or ground).
In plain terms: how much sun you actually get, and where panels go.
Everything you'll run, and roughly the daily energy.
In plain terms: what you're powering, in watt-hours a day.
Panel wattage and count to make that energy.
In plain terms: how much solar you need to generate.
Storage size and chemistry for your usage.
In plain terms: how much energy you bank for night and clouds.
Days without sun, and AC / DC coupling and inverter.
In plain terms: how long it rides through bad weather, and how it's wired.
System voltage and any generator or grid backup.
In plain terms: the backbone voltage, and your winter fallback.
You list the loads you want to run and describe your site; the tool works through the chain — daily energy, array wattage, battery storage, days of autonomy, system voltage, and inverter or coupling — and gives you a balanced spec instead of a guessed parts list.
A complete, downloadable system specification: site, loads, array, battery, autonomy and balance, and voltage and backup — sized together and formatted so an installer or distributor can quote it.
It's generated from your answers and reviewed for major physics violations — it won't hand you an array that can't charge the battery or an inverter that can't start your loads. Treat it as a strong starting point, not a substitute for an installer's site review and local code.
The tool is free to use and needs no account. You keep the spec.
Five minutes of plain questions. A build-ready system spec at the end.
Start your system spec →