MPPT vs PWM Solar Controllers

MPPT charge controllers are so efficient that some can reach 98% efficiency or better. But that doesn’t automatically make them better than PWM solar controllers. When comparing MPPT vs PWM charge controllers, you need to consider several other factors. 

Pulse-Width Modulation (PWM) and Maximum Power Point Tracking (MPPT) are both effective at controlling battery charging and preventing battery damage from overcharging and undercharging, but they’re completely different technologies. 

Each type works best under different conditions and deciding which is best for your needs will depend on several factors, such as:

  • The size of your solar array (maximum voltage/power produced)
  • Local climate conditions—PWMs work best in strong sunshine
  • The complexity of the system and any extra features you need
  • Budget—MPPT controllers are more expensive than PWMs

If you’re just getting started with solar power or are researching options for an installation, this guide is for you.

Don’t be put off by the high cost of installation. As the Minister for Climate Change and Energy Chris Bowen said,

“Renewable energy is the cheapest form of energy. The more renewable energy we have in the system, the cheaper bills will be.” – Chris Bowen

And don’t worry, this isn’t mind-bending “nerd speak,” even though we work hard on technical accuracy and detail.

This guide explores how PWM and MPPT solar controllers work, their characteristics, as well as their advantages and disadvantages.

We’ll also recommend where best to use either PWMs or MPPTs and where to buy quality models, so stick with us to the end.

1. Pros and Cons of PWM Charge Controllers

Victron BlueSolar PWM-Pro Charge Controller

Pros of PWM Charge Controllers

Pulse-Width Modulation (PWM) technology is simple and robust, which makes PWM charge controllers affordable and easy to use. 

Pulse-Width Modulation relies on the use of a digital switch (transistor) that controls how long power can flow. A longer “on time” means more electrical energy passes through. If the switch is off, no electricity passes through. 

PWM is one of the pioneering solar controller technologies. It is time-tested and highly reliable, and so long as you get a quality model with sufficient cooling (either using a fan or a metal heat sink), you can install it even in extreme conditions, such as the desert.

Cons of PWM Solar Charge Controllers

The simplicity of PWM charge regulators is also their biggest weakness. For one, they can’t regulate the input voltage from the solar panels. For example, a 12 V PWM charges the battery at 12 V regardless of the voltage the solar panel is producing.

Even if you connect 24 V panels to a 12 V PWM charge controller, it will bring down the output voltage to 12 V and the rest of the power will be wasted as heat. This reduces the system’s efficiency and can even damage the controller if the current is too high.

That’s why you must always match a PWM charge controller to the battery voltage and the solar array’s power rating (current and voltage). For example, the Victron PWM Solar Charge Controller below is rated for either 12 V or 24 V panels and 5 Amps of current.

Victron BlueSolar PWM Charge Controller

PWM charge controllers lose efficiency in cold temperatures or sub-optimal sunlight conditions.

They produce less power when there is no direct sunshine or if the panels are shaded. PWM controllers can’t adapt to such conditions and may stop charging the battery if the power production falls below a certain voltage.

But, despite their faults, PWM solar controllers have a big price advantage over MPPT controllers. You can usually get a good PWM charge controller for under $150, such as this Enerdrive ePOWER PWM Solar Controller. Also some cheaper portable solar panels you can get from some of the big box discounters often have a PWM solar controller included and whilst the panels efficiency likely isnt' first rate and PWM controller is basic an inefficient you can still get adequate results if you are a very casual user. For people going camping once a year over a weekend and say to make do with that but for anyone else you are better doing it right the first time. 

The table below compares the prices and main features of some PWM and MPPT charge controllers available at Off Grid Direct.

Solar Controller Type Example Price and Features
PWM Enerdrive ePOWER PWM Solar Controller

Price: $135.00

  • Rated for 12 V and 24 V systems
  • Rated for up to 30 Amps of current
  • Handles up to 450 Watts of power
  • LCD display
  • Works with sealed, flooded, and gel batteries
PWM Victron BlueSolar PWM-Light Charge Controller

Price: $81.45

  • Works with 12 V and 24 V systems
  • Overload, short circuit, and reverse polarity protection
  • Auto-disconnects at low battery voltage
  • Two-digit display
  • Lighting control function
MPPT Morningstar EcoBoost MPPT Charge Controller

Price: $559.00

  • Works with 12 V and 24 V systems
  • Load monitoring to prevent battery over-discharge
  • Rated for up to 1,120 Watts
  • Available in 20, 30, and 40 Amp ratings
  • Rated for up to 120 V input voltage
  • Rated for -400C to 600C
MPPT Victron SmartSolar 150V MPPT Charge Controller

Price: $1,457.18

  • Works with and auto-detects 12, 24, or 48 V systems
  • Can charge heavily depleted batteries, even at 0 V
  • Works with solar array voltage of 150 or 250 V
  • Rated for 70 Amps or 100 Amps
  • Remote control and configuration over Bluetooth or internet
  • Can be connected with other similar units

PWMs from reputable manufacturers are highly capable. But, although they provide a high level of battery protection, they work with low voltages and miss out on advanced features like remote monitoring. Understanding MPPTs will help make these differences clearer. 

2. Pros and Cons of MPPT Charge Controllers

Pros of Using MPPT Charge Controllers

In the video above, a solar specialist from Clean Energy Reviews talks about MPPT charge controllers. He compares common models available in Australia, including their prices and performance.

From the video, it’s clear that MPPT solar controllers have unique features such as input voltage monitoring and better output control. You can also change the conversion algorithm to match current weather conditions to maximise efficiency.

These advantages can make MPPT charge controllers more economical than PWMs in the long run, despite being more costly.

The way Maximum Power Point Tracking (MPPT) technology works is quite ingenious. MPPTs look at the input voltage from the solar array and the required battery voltage. Then, they run the input power through a transformer and convert it into low-voltage, high-current electricity at a level that best matches the battery’s charging needs.

This way, MPPTs always extract maximum power from the solar panels despite changing sunlight conditions and battery charging requirements. 

Morningstar EcoBoost MPPT Solar Charge Controller

Maximum power point tracking requires an algorithm that allows the controller to compute all the data it needs to operate efficiently despite changes in the amount of power produced.

Solar panels can produce more or less power depending on factors such as:

  • Solar irradiation — the amount of light energy falling on the panels
  • Temperature — high temperatures can lower panel efficiency and vice versa
  • Roof orientation — solar panels are most efficient when sunlight falls directly on them
  • Other factors — weather conditions, shading, type of solar panel, type of roof, and the condition of the solar panels can all affect efficiency

The ability to adapt to changing conditions to optimise charging is what makes MPPT charge controllers so effective. Victron claims its MPPT controllers can exceed 98% efficiency under ideal conditions.

This high efficiency allows MPPTs to continue charging the batteries even when conditions are not ideal. More power production means you can recoup your investment costs sooner, especially if you have a grid-tied system.

MPPT charge controllers can also handle solar arrays with a much higher voltage compared to the battery charging voltage. For example, the Victron SmartSolar MPPT below can handle a 150 V solar array to charge a 12, 24, or 48 V battery bank.

Victron SmartSolar 150V MPPT Charge Controller

The way MPPT charge controllers work allows for a high level of control over input and output power. This makes them ideal for large and complex solar installations.

High-end models also come with extra features that may be useful, such as built-in metering, LED displays, remote connectivity, and programmability. These features offer better monitoring and control for solar experts.

charge controller is the brain of your solar installation

Cons of Using MPPT Charge Controllers

Although MPPT technology was around as early as 1985, it’s only recently that MPPT controllers have become affordable and reliable enough for use in many solar installations. Even then, the price of MPPT controllers can exceed $1,000 for high-power applications.

For example, the Enerdrive ProStar MPPT Solar Controller below is rated for systems of up to 1,100 Watts of power and 40 Amps of current, but it’s quite expensive compared to a PWM.

ProStar MPPT Solar Controller

The technology used to manufacture MPPTs also requires more components, which makes them more likely to fail. MPPT charge controllers generally have a shorter lifespan compared to PWM models.

Since MPPT charge controllers operate above the battery voltage, sizing them for your system is challenging. They require precise calculations for proper voltage and current rating, and special components may be required to deal with the high voltage involved.

3. Where to Use PWM or MPPT Controllers

Morningstar EcoBoost MPPT Charge Controller with meter

The efficiency gain from using an MPPT charge controller, such as the one above, helps them produce maximum power. This makes them more economical than PWMs in the long run.

However, for small solar installations, the efficiency gains might be too little to justify a $500+ charge controller. Small installations (below 200 W) in tropical and subtropical regions may be served best by an appropriate PWM controller.

On the other hand, MPPT charge controllers operate at a higher voltage, which means lower current and power losses on long cable runs. Because you use smaller cables, material costs are lowered significantly.

From a technical point of view, the most important factors to consider when choosing between a PWM or MPPT charge controller include:

  • Installation size — use an MPPT if the system is high-voltage or exceeds 200 W, such as in solar farms
  • Site conditions — use an MPPT if you live in a temperate region, or if the batteries will be installed far from the solar array 
  • System components — some batteries, such as lithium models, work best with MPPT controllers that can provide the appropriate charging profile
  • Type of installation — if your system is grid-tied, you must use MPPT controllers since PWMs are best used in 12 V or 24 V off-grid installations 

Budget constraints can also be a major factor. If both PWM and MPPT controllers can work for your installation, buying a PWM controller can save you some money. PWMs can be two to three times cheaper than MPPTs of a similar capacity. 

Expert Tip: If performance and reliability are important to you, buy high-quality MPPT charge controllers from a major brand like Victron or Enerdrive. Cheap MPPTs are often made with low-quality components that are more likely to fail. 

4. Which Are Better, PWM or MPPT Charge Controllers?

Victron BlueSolar PWM-Pro Charge Controller

Even though MPPT charge controllers seem to be superior in many respects, PWMs also perform very well in the right conditions. We can’t say that one type is superior to the other unless we consider the conditions under which they’re meant to be used.

What we can say is that MPPT controllers are more efficient than PWM models. An MPPT charge controller can help you harvest up to 15% more power in winter and 30% more in summer.

PWM controllers might be preferable for their reliability, but their limitations mean you have to use an MPPT charge controller for installations that require the use of three or more panels, or in temperate regions that get inconsistent sunshine.

Get Charge Controllers You Can Trust From Off Grid Direct

You may know by now what type of solar charge controller you need. The important question is, which brand will you buy?

We’ve emphasised the importance of buying high-quality, reliable brands for good reason. A charge controller is the brains of your solar installation, and is responsible for protecting your expensive batteries and other components.

At Off Grid Direct, we take the worry out of the equation by only bringing you solar system components from manufacturers we have tried, tested, and come to trust. 

Find your solar charge controller now to take advantage of our price match guarantee, and enjoy free delivery for orders above $300 within mainland Australia.

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