A full example
| Water level 70 m + drawdown 15 m + rise 5 m + friction 10 m | TDH = 100 m |
| Hydraulic power: 40 m³/h × 100 ÷ 367 | 10.9 kW |
| Motor input: 10.9 ÷ (0.65 × 0.85) | 19.7 kW |
Panels are then calculated from daily energy and your city's worst month, and compared with the company rule (1.3 kW of panels per HP). By that rule a 100 HP motor needs 130 kW, or 200 panels at 650 W.
Common mistakes
- Ignoring drawdown, so the well seems shallower than it runs.
- Ignoring cable length and voltage drop.
- Assuming constant flow through the day, when it follows the sun.