Amperage Labs
Off-Grid Solar, Battery, & MPPT Sizing Tool
System parameters.
Enter your loads in two groups. 230V mains appliances go under AC Loads. Devices running directly off the battery go under DC Loads.
Fans, TV, fridge, lights — anything plugged into a wall socket
12V DC lights, USB chargers, DC fans wired directly to battery
This is the Effective Daily Load used in all sizing calculations.
Voltage: 12V hobby vs 48V microgrid
Chemistry: DoD battery wear limits
Autonomy: stormy day safety buffer
PSH: effective hours of maximum solar intensity
Sets how much battery capacity can be used safely. Lithium defaults to 80% (0.80); Lead-Acid defaults to 50% (0.50).
Peak Sun Hours reference.
PSH varies by location, season, and panel tilt. These are annual daily averages for a south-facing panel at optimal tilt. Use the regional presets in the calculator above, or enter a custom value for your location.
For precise values at your exact coordinates and panel orientation, use Global Solar Atlas or EU JRC PVGIS.
Sizing analysis.
Load in all formulas below = Effective Daily Load from the System Parameters section.
Total capacity required in watt-hours.
Battery rating at chosen system voltage.
Minimum charge controller size. We recommend rounding up to next standard rating.
Shop MPPT controllers →Estimated sunny days to fully replenish the battery bank after a complete autonomy-period discharge, assuming the recommended array size and daily load still running.
Off-grid battery sizing tips.
- Tropical & Dusty Climates: In Bangladesh and similar climates, temperature derating is minimal — but dust and haze can reduce panel output by 10–15%. Use a slightly conservative PSH (try 4.0 instead of 4.5) or plan to clean panels monthly.
- Autonomy Days: For load-shedding backup where grid returns within 12–24 hrs, 1 day of autonomy is usually sufficient. For fully off-grid rural systems, size for 2–3 days to survive consecutive overcast days.
- Inverter Overhead: A typical 1000W pure-sine inverter draws 10–20W at idle even with no load. For a 24h system, that adds 240–480 Wh/day — include this in your Daily Load input before sizing.
- Battery Chemistry: LiFePO4 lasts 2,000–5,000 cycles vs 300–500 for Lead-Acid, making it cheaper long-term despite the higher upfront cost. Browse LiFePO4 batteries →
- AC Load Correction: This calculator sizes the battery for energy drawn from the battery terminals — not energy consumed at the plug. If your loads run through an inverter (230V AC appliances), your battery must supply roughly 8–10% more than your appliances actually consume, because inverters are not 100% efficient. A home consuming 1,200 Wh/day at the plug draws approximately 1,200 ÷ 0.92 = 1,304 Wh/day from the battery. Enter the battery-side figure here for accurate sizing.
Methodology & assumptions.
Every output is traceable to a named formula. Read the full derivations, assumptions, and scope of this calculator.