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AESV worksheet
Solar Generator & Battery Backup Sizing Worksheet
Use this quick planning worksheet to estimate daily energy load, backup battery capacity, solar array size, and minimum charge controller rating. This is a planning estimate, not a final electrical design.
Core sizing formulas
1. Daily load
Watts × hours used per day = watt-hours per day
Watts × hours used per day = watt-hours per day
2. Battery storage
Daily load × 1.5 reserve margin = suggested storage
Daily load × 1.5 reserve margin = suggested storage
3. Solar array
Daily load ÷ peak sun hours × 1.25 = suggested panel watts
Daily load ÷ peak sun hours × 1.25 = suggested panel watts
4. Charge controller
Solar array watts ÷ battery voltage × 1.25 = minimum amps
Solar array watts ÷ battery voltage × 1.25 = minimum amps
Example
For a 400W average load running 8 hours/day: daily load is 3,200 Wh. With reserve margin, battery storage target is about 4,800 Wh. At 5 peak sun hours, solar array target is about 800W. On a 24V battery bank, minimum controller rating is about 42A, so a 50A MPPT class controller is the safer starting point.
Quick reference
Peak sun hours by region:
Southwest US / Australia: 5–6 hrs
Southeast US / Mediterranean: 4–5 hrs
Northern Europe / Pacific NW: 3–4 hrs
Common battery voltages:
12V (small kits), 24V (mid systems), 48V (large home backup)