Solar charge controllers are essential components in both residential and commercial solar systems. These devices monitor and adjust the flow of energy that travels from a solar array into a battery bank.
Not all solar charge controllers have the same mechanisms for monitoring this flow. There are two main types of controllers for residential applications: MPPT and PWM.
The two types of controllers perform similar functions, but they also exhibit some striking differences. The best solar charge controller for your system will depend on whether you want to prioritise advanced technology and higher efficiency or a budget-friendly option.
Why Do You Need a Solar Charge Controller?
There are a variety of reasons that you need a charge controller for your solar system. First and foremost, solar charge controllers regulate energy flow from a solar array into the batteries. Without one, you could risk a surge that fries the system. They also contain safety features that prevent failures or fires in your battery bank, wiring, and other components.
Overload or overcurrent protection is an essential function provided by solar charge controllers. Solar panels produce more power than a battery bank can handle. A battery can catch fire or otherwise malfunction when large power spikes occur. Overload protection prevents this danger from happening—instead of a battery malfunctioning, a fuse or breaker absorbs the excess power.
Low Voltage Disconnects
Attempting to draw power from a dead battery can cause irreversible damage. Solar charge controllers feature a low-voltage disconnect feature. When the battery reaches a set voltage indicating that you’ve depleted its charge, the charge controller will disconnect the battery and prevent further use.
Once the battery is above the “dead” threshold again, the charge controller will reconnect it and allow it to provide power again.
Block Reverse Currents
Electrical current should only run in one direction in a solar setup: from the solar panels to the battery. Without a charge controller, power has the potential to run from the battery back to the panels. A solar charge controller acts as a valve, creating a one-way path for current to travel.
Which Is Better: MPPT or PWM Solar Charge Controllers?
When it comes to efficiency, operating temperature, and cost, MPPT and PWM solar charge controllers differ widely.
MPPT (Maximum Power Point Tracking)
MPPT (Maximum Power Point Tracking) controllers are a newer, more advanced technology. They utilise a variety of features that make them a better choice over PWM controllers in most applications.
MPPT technology has existed for a few decades but has only recently evolved to become affordable for the average homeowner. Many estimates have determined that using an MPPT charge controller can increase system efficiency by up to 30%.
Solar panels usually provide an excess voltage to the battery bank. MPPT controllers can convert this excess voltage into more amperage for the batteries. It reduces charging time and increases the amount of energy produced by a solar array. This function is sometimes referred to as a “boost.”
MPPT charge controllers also can handle varying voltages. In some instances, installing a mix of solar panels (some with 24V, some with 48V) can be useful. A combination of different voltage solar panels can provide power to large appliances and high-energy use systems. This demand would be impossible to accommodate when using a PWM controller. However, MPPT technology makes it possible to mix and match this way.
Peak sun hours are at their lowest in the winter. Cold, cloudy days can increase the power solar panels generate. Despite fewer daylight hours, the colder temperatures increase efficiency by preventing the system from overheating. MPPT controllers enhance this efficiency, collecting extra energy from cold solar panels and keeping the batteries charged over winter.
MPPT technology is standard in most residential solar applications. EcoFlow Solar Generators are one example—they combine a charge controller, battery bank, and more into one compact power station—and at least one solar panel is included!
- Temperature Adaptability: MPPT controllers work well in a wide range of climates, including extreme cold and heat.
- Efficiency: MPPT controllers can convert excess voltage into more amps for a battery. This results in more efficient use of your solar array and more power generation.
- System Size: MPPT controllers work equally well with large, complex systems (such as a home array with varying voltages) and small systems (such as an RV array like EcoFlow’s Power Kits).
- Higher Upfront Cost: MPPT controllers are more expensive than PWM.
PWM (Pulse Width Modulation)
PWM (Pulse Width Modulation) controllers are a cheaper, less-advanced technology. They were popular in the first wave of residential and RV solar systems. However, MPPT controllers have decreased in price and are replacing PWM in most applications.
“Pulse width modulation” refers to the controller’s function of slowly reducing the current as the batteries are charging. PWM controllers will continue to allow a trickle of current to charge a battery when it reaches maximum voltage. In other words, they will continuously provide a small amount of power to keep the batteries topped up.
PWM controllers can only utilise the voltage that matches your battery bank. For example, most PWM controllers are integrated with a 12V battery system. If your solar array is providing 18V, then that extra 6V of power will be wasted.
PWM controllers may be suitable for small systems. In these cases, the potential benefits of an MPPT controller may not outweigh the higher upfront cost.
- Cheaper Cost: PWM charge controllers are more affordable than MPPT.
- Warm Weather: PWM controllers perform well when the connected panels operate in warm, sunny weather.
- Not Cold Tolerant: PWM controllers lose efficiency when temperatures are cold.
- Inefficient: Excess voltage produced by the solar panels goes to waste with a PWM controller.
What Is the Advantage of MPPT Over PWM?
MPPT controllers are more efficient than PWM. They convert excess voltage into more amps, resulting in up to 30% more power generation. A system that uses an MPPT controller can gather more power from the same amount of panels. You can install fewer panels than a PWM system or enjoy the extra energy that your MPPT charge controller provides.
MPPT controllers perform much better in extreme cold and heat. Their temperature adaptability makes them a more durable and versatile option, particularly for areas with temperature fluctuations. PWM controllers tend to lose efficiency as the climate deviates from room temperature. They will be at a significant disadvantage unless you live in perfect year-round temperatures.
Complex solar arrays will require the use of an MPPT controller. With PWM technology, using 48V panels with a 12V battery bank is not possible. However, an MPPT controller can convert this excess voltage into more usable amperage for your 12V batteries.
Similarly, you may wish to use panels of varying voltages in your solar arrays, such as 12V, 24V, and 48V panels. Combining panels with varying voltages is only possible if you route them through an MPPT controller.
What Are the Disadvantages of MPPT?
MPPT charge controllers will generally cost a bit more than comparable PWM controllers. The difference is negligible, as the extra power generation will quickly compensate for the slight cost difference.
Another possible disadvantage of MPPT controllers is that they utilise speciality voltage and temperature sensors. While these sensors allow them to perform better, they are also extra components that have the potential to wear down or need replacing. PWM controllers contain simpler circuitry that is less prone to wear and tear.
Key Considerations When Choosing Between MPPT and PWM
There’s more than the cost to consider when choosing the right solar charge controller for your system.
Conversion efficiency is one of the most significant considerations when choosing a solar charge controller. MPPT controllers provide battery banks with up to 30% more charge (depending on the rest of your system’s components). The conversion efficiency is a clear advantage over PWM charge controllers.
Does Your System Already Include a Charge Controller?
Some solar systems may already include a charge controller. For instance, EcoFlow Power Kits include five components in one package. An MPPT controller is integrated into the power kit, in addition to AC outlets, a battery bank, an AC/DC smart distribution panel, and more.
Solar Array Size
The size of your solar array can affect whether you require an MPPT controller’s advantages. For instance, a 5 or 10-watt solar panel that feeds a 12V battery will not require an MPPT controller. A system this small will not utilise the advanced technology, and you would be better off saving money and going with a PWM controller.
Once your array grows to a few-hundred watts or more, the benefits of an MPPT controller become clear. You will notice the extra efficiency—your batteries will charge up to 30% faster and produce more energy from the same amount of solar panels.
If you have limited roof space, an MPPT controller will also help you gather every watt of energy from your smaller array.
Your region’s climate can affect your choice of controller. If you live in Arizona or Southern California, you may receive full, direct sunshine nearly every day of the year. The constant sun exposure may lessen your need for the efficiency of an MPPT controller. However, those in cold and dreary climates will undoubtedly enjoy the extra power that an MPPT controller can help produce.
The price should be a lesser consideration when choosing a charge controller. Anyone installing a residential solar system should make room for an MPPT charge controller in their budget.
That’s not to say cost isn’t a factor, particularly considering the cost of a typical residential solar system. PWMs are more cost-friendly upfront. That said, an MPPT has higher efficiency, which means you stand to get more power from your system and yield higher returns over the long term when you install one.
Which Solar Charge Controller Is Right for You?
For consumer solar systems, there are only two choices of charge controllers: MPPT and PWM. The two types of controllers perform similar functions. However, MPPT has some clear advantages, especially over time.
Crafting your solar power system out of individual components can quickly become overwhelming. All-in-one solar setups are available to eliminate the research and concerns about compatibility that come with trying to install your own system. With the EcoFlow Smart Home Ecosystem, you can customise your home solar power solution with highly efficient solar generators with MPPT charge controllers and other smart technologies already built-in.