Amperage Labs.

Amperage Labs

Off-Grid Solar, Battery, & MPPT Sizing Tool

System parameters.

Wh

Load: 24h consumption

System Voltage V (DC)

Voltage: 12V hobby vs 48V microgrid

Battery Chemistry Chemistry

Chemistry: DoD battery wear limits

Days of Autonomy Days

Autonomy: stormy day safety buffer

hrs

PSH: effective hours of maximum solar intensity

80%
Default for Lithium

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.

Region PSH (avg) Range
Bangladesh 4.5 4.0 – 5.5
India (South) 5.0 4.5 – 6.0
Sub-Saharan Africa 5.5 5.0 – 7.0
Middle East 6.0 5.5 – 7.5
USA (Southwest) 5.5 5.0 – 7.0
USA (Average) 4.0 3.0 – 5.5
Southern Europe 4.5 4.0 – 5.5
Central Europe 3.0 2.5 – 4.0
UK & Ireland 2.5 2.0 – 3.5
Australia 5.0 4.0 – 6.5

For precise values at your exact coordinates and panel orientation, use Global Solar Atlas or EU JRC PVGIS.

Sizing analysis.

Required Battery Energy
1,500 Wh

Total capacity required in watt-hours.

Required Battery Capacity
62.5 Ah

Battery rating at chosen system voltage.

Battery Energy Allocation
Usable Energy 1,200 Wh (80%)
Reserve Capacity 300 Wh (20%)
Recommended System Hardware
Solar Array Rating
390 W

Estimated solar array size assuming 30% system losses.

Shop solar panels →
MPPT Controller Size
16.3 A

Minimum charge controller size. We recommend rounding up to next standard rating.

Shop MPPT controllers →
Recharge Time
6.7 days

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 →

Methodology & assumptions.

Every output is traceable to a named formula. Read the full derivations, assumptions, and scope of this calculator.

Read more →