Inputs stay on your device
The first release has no account, database, or calculation API.
Solar and battery planning tools
Useful answers,
with the losses shown.
Size a battery bank, check runtime, plan a solar array, or map a series-parallel layout. Every estimate shows the assumptions and the upward rounding behind it.
No account Runs locally Assumptions stay editable
A calculator should show its work
Presets are starting points
Depth of discharge and efficiencies remain visible and editable.
Hardware counts round up
The tool recalculates capacity from the whole number of batteries or panels.
Popular planning paths
Choose the next question
Start with the situation you are trying to plan, then carry the same visible assumptions into the next calculator.
Plan outage backup
List essential appliances and estimate energy, running watts, surge, and battery capacity.
Estimate solar charging time
Start from a battery state of charge and panel power, including peak sun hours and finishing time.
Plan an RV solar system
Combine RV loads, storage, solar panels, and a controller-current baseline in one scenario.
Thirteen focused calculators
Start with the question you have
You do not need to know every electrical term first. Choose the task closest to your current decision.
Solar battery size and bank calculator
Turn daily energy and autonomy days into nominal kWh, Ah, and a whole-module battery bank.
Battery runtime calculator for Ah, Wh and watts
Estimate LiFePO4, AGM, and solar battery runtime from capacity, load watts, usable depth, and inverter losses.
Solar battery charging time calculator
Estimate equivalent charging sun and solar days from battery capacity, state of charge, panel watts, losses, and finishing-stage time.
Battery backup calculator
Build an appliance list and size the energy storage needed for an outage.
Solar load calculator
Total appliance watts, quantity, daily run time, and listed surge before sizing batteries or panels.
Off-grid solar system calculator
Combine an editable appliance load, battery autonomy, solar coverage, panel count, and controller current baseline in one transparent plan.
Battery series and parallel calculator
Check voltage, Ah, energy, battery count, and the shape of a series-parallel layout.
Solar panel series and parallel calculator
Calculate array Voc, Vmp, Isc, Imp, panel count, and optional cold-weather Voc.
Solar panel size and kWh calculator
Convert daily or monthly kWh into array watts and whole panels using peak sun hours and losses.
Solar panel roof space calculator
Compare portrait and landscape panel counts inside a measured usable roof rectangle.
Solar panel output calculator
Estimate daily, monthly, and yearly energy from an array you already have.
Solar panel efficiency calculator
Calculate rated module efficiency from panel watts, face area, and an explicit irradiance condition.
Solar charge controller calculator
Calculate cold-corrected array Voc, PV input current, output current, and minimum documented controller limits.
Solar panel tilt and azimuth calculator
Compare practical tilt and azimuth candidates with PVWatts location weather and quantify the modeled energy difference.
RV solar calculator
Plan RV loads, battery storage, solar panels, and a controller current baseline together.
Transparent by default
Formulas, presets, and rounding live in one methodology
The methodology page records the units, default planning factors, formula version, and how installable counts are rounded. Tool results link back to the matching section.