Solar Array Sizing
N = E_daily / (G_peak × η × PSH)
Quick answer
This calculator solves N = E_daily / (P_panel × η_system × PSH) for Number of Panels. With Daily Energy Need 0.5 kWh, Panel Peak Power 800 W/m², System Efficiency 1.1, Peak Sun Hours 5 h, the result is 0.1136.
Calculator
Formula
Description
Solar array sizing determines how many panels are needed to meet a daily energy requirement. The calculation divides the daily energy consumption by the product of each panel peak power rating, the overall system efficiency (accounting for inverter losses, wiring losses, soiling, and temperature derating), and the peak sun hours for the location. Peak sun hours represent the equivalent number of hours at 1000 W/m² irradiance that produce the same daily energy as the actual varying irradiance profile.
Variables
- N — Number of solar panels required
- E_daily — Daily energy consumption (Wh)
- P_panel — Peak power rating per panel (W)
- η — Overall system efficiency (0-1)
- PSH — Peak sun hours for the location (hours)
Practical Notes
Peak sun hours vary dramatically by location and season: 3-4 in northern Europe, 4-5 in the central US, and 5-7 in desert regions. Always round N up to the next whole number and add 10-20% margin for cloudy days and degradation over time. Panel output degrades about 0.5% per year, so after 25 years a panel produces about 87% of its original rating.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| N | Number of Panels | — | — |
| E_daily | Daily Energy Need | Wh | Wh, kWh |
| G_peak | Panel Peak Power | W/m² | — |
| eta | System Efficiency | — | —, % |
| PSH | Peak Sun Hours | h | — |
Step by step
- 1. What you know: Daily Energy Need 0.5 kWh, Panel Peak Power 800 W/m², System Efficiency 1.1, Peak Sun Hours 5 h
- 2. The relation: N = E_daily / (P_panel × η_system × PSH)
- 3. Substitute: E_daily = 0.5 kWh, G_peak = 800 W/m², eta = 1.1, PSH = 5 h
- 4. Result: Number of Panels = 0.1136
Worked examples
Minimum range
Given: Daily Energy Need 1 Wh, Panel Peak Power 10 W/m², System Efficiency 5.5 %, Peak Sun Hours 0.1 h
Result: Number of Panels = 18.18
Low range
Given: Daily Energy Need 10 Wh, Panel Peak Power 100 W/m², System Efficiency 0.55, Peak Sun Hours 1 h
Result: Number of Panels = 0.1818
Typical
Given: Daily Energy Need 0.5 kWh, Panel Peak Power 800 W/m², System Efficiency 1.1, Peak Sun Hours 5 h
Result: Number of Panels = 0.1136
High range
Given: Daily Energy Need 5 kWh, Panel Peak Power 1000 W/m², System Efficiency 1.76, Peak Sun Hours 24 h
Result: Number of Panels = 0.1184
Maximum range
Given: Daily Energy Need 50 kWh, Panel Peak Power 10000 W/m², System Efficiency 17.6, Peak Sun Hours 240 h
Result: Number of Panels = 0.001184
How Number of Panels changes with Daily Energy Need
| Daily Energy Need (input) | Number of Panels (result) |
|---|---|
| 50 Wh | 0.01136 |
| 125 Wh | 0.02841 |
| 0.25 kWh | 0.05682 |
| 0.375 kWh | 0.08523 |
| 0.5 kWh | 0.1136 |
| 0.75 kWh | 0.1705 |
| 1 kWh | 0.2273 |
| 2 kWh | 0.4545 |
| 3.5 kWh | 0.7955 |
| 5 kWh | 1.136 |
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<p><a href="https://vbatpower.com/formulas/solar-array-sizing/">Solar Array Sizing</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Solar Array Sizing?
Use N = E_daily / (P_panel × η_system × PSH). With Daily Energy Need 0.5 kWh, Panel Peak Power 800 W/m², System Efficiency 1.1, Peak Sun Hours 5 h, Number of Panels works out to 0.1136.
What is the formula for Solar Array Sizing?
The formula is N = E_daily / (P_panel × η_system × PSH). Solar array sizing determines how many panels are needed to meet a daily energy requirement.
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