Enter your array power and battery voltage. We'll size the controller with a safety margin for cold-weather voltage spikes.
MPPT lets you wire panels in a higher-voltage string than your battery, which cuts cable losses and usually harvests more energy — PWM requires the panel voltage to roughly match the battery voltage.
Further reading: Off-Grid Solar 101: What It Actually Takes to Leave the Grid
The safety margin exists because a panel's actual output current can briefly exceed its rated figure — cold, bright, and clear days especially — and because manufacturers de-rate continuous-duty controllers below their absolute peak. 25% is the industry-standard margin quoted by most controller manufacturers and matches the approach used in the NEC (National Electrical Code) for continuous DC loads.
Not recommended — controllers are usually the cheapest component to slightly oversize, and clipping current on a bright, cold day is a common cause of underperformance and premature failure.
Yes — a higher current rating typically means a larger cable is needed between the array and controller. Check the Solar Cable Size Calculator once you know your controller's rated current.