Solar Panel Calculator (Watts per Day)

Calculates the number of solar panels needed based on daily energy consumption, peak sun hours, and system efficiency. Also sizes battery capacity for autonomy. Worked example: a home using 5 kWh/day at 5 peak sun hours needs 5000/(400 x 5 x 0.75) = 3.3, so four 400 W panels cover the load with margin for cloudy days. Winter planning: if December delivers only 60 percent of average sun hours, either multiply the array by 1.6 or accept generator backup - the calculator makes that trade-off explicit before you buy.

1. 1

   Step 1

   Enter your daily energy consumption (Wh)

2. 2

   Step 2

   Specify average peak sun hours for your location

3. 3

   Step 3

   Select system voltage (12V, 24V, 48V)

4. 4

   Step 4

   Enter the wattage of your chosen panels

• 1

  Peak sun hours vary by location (typically 4-6 hours)

• 2

  Include 20-30% for system losses and inefficiencies

• 3

  Higher voltage systems reduce cable losses

• 4

  Plan for 2-3 days of battery autonomy for off-grid

• Using total daylight hours instead of peak sun hours

• Forgetting inverter and charge controller losses

• Under-sizing batteries for cloudy day autonomy

• Not accounting for seasonal sun hour variations