Sizing & selection

Choosing the right charge controller determines the efficiency and longevity of your off-grid solar system. An undersized controller will limit your production, while an outdated PWM model will cause you to lose 20-30% of energy compared to a modern MPPT.

This sub-category guides you through the selection and optimal sizing process: PWM vs MPPT (when to choose which?), calculating the required regulator current, choosing the system voltage (12V/24V/48V), and comparing the leading brands (Victron, Epever, Renogy, Morningstar).

PWM vs MPPT: understanding the fundamental difference. PWM (Pulse Width Modulation) regulators are simple and economical (£30-80), but are only suitable for small installations (<300Wp) with low-voltage panels (Vmp close to Vbat). MPPT (Maximum Power Point Tracking) controllers extract 15-30% more energy by converting excess panel voltage into battery charging current. An essential investment for systems above 400Wp.

How to size the MPPT current? Simplified formula: Controller current (A) ≥ (Panel power Wp × 1.25) / Battery voltage V. Example: 800Wp / 24V × 1.25 = 42A → minimum 50A regulator. Always allow a 20-25% margin for future developments and peak production.

12V, 24V or 48V? 12V system up to 800Wp (motorhomes, boats). 24V from 800 to 2000Wp (tiny houses, shelters). 48V above 2kWp (off-grid homes). The higher the voltage, the lower the Joule effect losses over long distances.