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MPPT vs PWM solar charge controller: which one do you need?

Both charge a battery from solar panels. One of them gets noticeably more energy out of the same panels.

What a charge controller does

A charge controller sits between the solar panels and the battery. It stops the battery from overcharging and controls how much current flows in. In off-grid systems and solar inverters with batteries, it is the part that decides how much of your panels' power actually reaches the battery.

How PWM works

A PWM (pulse width modulation) controller connects the panel almost directly to the battery and switches it on and off rapidly. The panel is forced to work at the battery's voltage, not at its own best voltage. That wastes part of the panel's output.

How MPPT works

An MPPT (maximum power point tracking) controller keeps finding the voltage at which the panel gives the most power. It then converts that higher voltage down to the battery voltage and turns the difference into extra charging current.

Side by side

Which should you choose?

Choose MPPT if your panels are large modern modules (their voltage is much higher than a 12 V or 24 V battery), if your system is more than a few hundred watts, or if you have a lithium battery.

PWM is enough for a small setup, such as one small panel charging a 12 V battery for lights, where the panel voltage is matched to the battery.

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