Off-grid & Solar Calculators
Size your system before you load the rig.
Field-grade calculators for solar arrays, battery banks, inverters, and backup runtime — no spreadsheets, no guesswork, no dead batteries at 2 a.m.
Start here
Every off-grid build begins with the battery bank. Size it first and the rest of the system falls into place — array, inverter, and charge controller all follow from the amp-hours you need. Try the featured calculator below with the pre-filled example, then explore the full toolkit beneath it.
Featured calculator — Battery Bank Sizing
The calculators
Each one is instant and runs entirely in your browser — US units, nothing stored.
Solar Array Sizing
How many watts of panel you need to refill the bank by sundown.
Open calculator BatteryBattery Bank Sizing
Amp-hours and kWh of battery for your daily load and days of autonomy.
Open calculator InverterInverter Sizing
Match continuous and surge watts to your real appliance loads.
Open calculator ChargeCharge Controller Sizing
Pick the right MPPT amp rating for your array and bus voltage.
Open calculator BackupBattery Backup Runtime
How long the bank keeps the lights on when the grid drops.
Open calculator ConvertWatt-Hour / Amp-Hour
Convert between Wh and Ah at any system voltage.
Open calculator OutputSolar Output Estimate
Daily and yearly kWh from system size and peak sun hours.
Open calculator LoadOff-Grid Load Calculator
Add up your appliances to get daily watt-hours — the start of every sizing job.
Open calculator WiringSolar Wire Size
DC cable gauge for your run length, current, and voltage drop.
Open calculator GeneratorGenerator Sizing
Running and starting watts from your appliance list.
Open calculator SolarPanel Tilt Angle
Best tilt for your latitude — year-round, summer, and winter.
Open calculator CostSolar Payback Period
Years to break even from system cost and annual energy savings.
Open calculatorWhy off-gridders use SunReckon
Sizing an off-grid or backup power system shouldn't take a spreadsheet and a forum deep-dive. SunReckon puts the real field math — panel watts, battery amp-hours, inverter surge, charge-controller amps, backup runtime — in one place, in the US units gear is actually sold in.
- Field-grade & private: everything runs in your browser; nothing you type is stored or sent.
- Chem-aware math: depth-of-discharge and efficiency handled for lead-acid and LiFePO₄, on 12 / 24 / 48 V buses.
- Honest defaults: realistic example values are pre-filled so you can see how each tool behaves, then drop in your build.