Regulation
Charge Controllers
Sits between panels and battery in an off-grid or hybrid system. MPPT harvests roughly 20-30% more from the same array than PWM, and lets you run higher-voltage panels on thinner cable.
What to compare
- MPPT versus PWM — MPPT pays for itself above about 200W of array
- Current rating with headroom over your array's output amps
- Input voltage window must accept panel Voc at your coldest temperature
- Number of independent MPPT trackers
How to size it
Size by current, not by panel wattage. Divide total array watts by battery bank voltage to get amps, then multiply by 1.25 for the NEC safety factor: a 3,000W array on a 48V bank is 62.5A, so 78A after the factor, and you buy the next size up — typically 80A or 100A. On a 12V bank the same array would need over 300A, which is why anything beyond a modest system moves to 24V or 48V. Higher bank voltage means lower current, thinner cable and a cheaper controller.
Mistakes that cost money
- Choosing PWM to save money
- PWM drags the panel down to battery voltage and throws away the difference. MPPT converts the excess voltage into extra current and typically harvests 20-30% more from the same array, with the gap widening in cold and low light. On anything above roughly 200W the MPPT premium pays back quickly.
- Forgetting cold-weather voltage
- Open-circuit voltage rises as temperature falls. A string that measures comfortably inside the controller's limit in July can exceed it on a clear January morning and destroy the input. Size the string against your record low, not against today.
- Undersizing for future expansion
- Controllers are cheap relative to the labour of replacing one. If there is any chance of adding panels later, buy the capacity now rather than rewiring the system twice.
Options
No charge controllers listed yet. We only list components we can price and specify accurately, and we are still onboarding retailers for this category.
The guides below cover how to choose one in the meantime — they are what we would tell you before recommending any specific product.