What’s The Difference Between MPPT & PWM Solar Charge Controllers?


You might have heard that overcharging a battery will reduce its capacity. We know this applies to our phones, our laptops, and our car batteries—but did you know that it’s also important for your solar array?

If you have an off-grid solar system, you rely on a battery storage system to store excess power that can be used at night or on cloudy days. Given the high cost of solar batteries and their importance for your PV system, you want to preserve them for as long as possible. 

That’s where your charge controller comes in. There are two types of charge controllers—how do you know which one is best for your system? We’re going to break down the main differences between them:


Pulse-Width Modulation Charge Controllers

These controllers work by moderating the rate at which the battery receives power. As the battery reaches its capacity, the PWM controller begins to taper off the current it sends. It switches (or pulses) between states of charging and not charging, which effectively regulates how much power the battery receives. 

A PWM controller strikes a balance between supplying the battery with adequate power, but not enough to overload it.


When Should You Choose a PWM Controller?

  • You’re looking for a budget-friendly solution. PWM controllers are more affordable than MPPT ones—typically, they’re a fraction of the cost. This is due to their simpler technology.

  • You have a smaller solar system. If you’re only producing a small amount of power, you won’t need a complex charge controller to regulate it; a PWM one will work just fine. With a smaller solar array, the increased efficiency of an MPPT controller will make a minimal difference.


  • Your panels and battery have the same voltage. For this charge controller to work properly, the voltage of both the solar modules and the battery needs to be equal.


Maximum Power Point Tracking Charge Controllers

An MPPT controller constantly monitors the output of the panels and the capacity of the battery to reach the maximum power point. These controllers account for the voltage of the panels and the voltage of the battery. 

By optimizing the voltage level of the battery and the solar modules, an MPPT charge controller can increase efficiency by up to 30%. This charge controller moderates the current that the battery receives to prevent it from being overloaded and to reduce any energy loss.


When Should You Choose an MPPT Controller?

  • You want to increase the efficiency of your energy production. The efficiency of these controllers pays off when conditions are less than favourable for solar production, like on cloudy days or during seasons with fewer hours of sunlight.


  • You have a larger solar system. It’s easier to scale up your PV system when you use an MPPT charge controller; you won’t be limited by the voltage of your battery.


  • The voltage of your solar panels is higher than the voltage of your batteries. Without an MPPT controller, your panels may feed too much power into the battery and cause it to overload. 


Still undecided about which charge controller you need? You can refer to this charge controller flow chart.


Setting Up Your Solar System

Both of these controllers can greatly increase the efficiency and lifespan of your solar system batteries. However, the one best-suited for your setup will vary based on your budget, the size of your solar array, and the climate you live in.

Looking for solar companies in Winnipeg? At Powertec Solar, we’re committed to providing our customers with high-quality, reliable solar systems. Contact us today for a free solar feasibility analysis.