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

Updated October 2026

A charge controller sits between the panels and the battery and stops the battery from being overcharged. The two common types, PWM and MPPT, handle the panel voltage very differently, and that decides how much of your panel power actually reaches the battery.

How each one works

• PWM connects the panel straight to the battery and switches on and off to limit charging. The panel is pulled down to the battery voltage, so any extra panel voltage is wasted.
• MPPT converts the extra voltage into extra current, so the panel can run at its best operating point while the battery gets a lower voltage and a higher current.

Example: one 100 W panel on a 12 V battery

A typical 100 W panel runs at about 18 V and 5.6 A. A 12 V battery being charged sits near 13 V.

This is a best case for MPPT because the voltages are far apart. Over a full year most systems gain 10 to 30 percent more energy with MPPT, and more in cold weather, when panel voltage rises.

Which should you choose?

• PWM: small 12 V systems up to about 200 to 300 W, with panels made for 12 V charging, where low cost matters most.
• MPPT: everything larger, any 24 V or 48 V battery bank, any system with higher-voltage residential panels, and any site with cold winters or long cable runs.

Sizing an MPPT controller

1. Current. Array watts ÷ battery voltage, then add 25 percent. Example: 1200 W ÷ 48 V = 25 A, × 1.25 = 31 A, so choose a 40 A controller.
2. Input voltage. Add up the open-circuit voltage (Voc) of the panels wired in series and multiply by 1.2 for cold mornings. The result must stay under the controller's maximum PV voltage.
3. Battery voltage. Check that the controller supports your 12, 24 or 48 V bank and the battery chemistry, such as LiFePO4 or lead-acid.

Next step: size your array in the calculator, then see matching controllers and parts.