A Guide to Selecting the Perfect Solar Controller

Solar controllers, solar charge controllers, or solar regulators, are critical components of standalone solar energy systems. On average, a single 12-volt solar panel will produce between 12 and 21 volts of electricity. If a battery were exposed to such high voltage, it would overcharge, causing lasting damage.

Solar controllers prevent battery damage by regulating voltage and reducing it to a safe level. Two main types of solar controllers exist—pulse width modulation (PWM) regulators and maximum power point tracking (MPPT) regulators. Both types of controllers can be purchased from reputable global distributors such as RS Components.

PWM regulators

PWM regulators have long held the title of the most common kind of battery charging technology. These specialised regulators can prolong battery life and reduce sulphation and heating while charging.

While PWM charge controllers are usually cheaper than MPPT regulators, they are also less efficient. MPPT regulators are up to 30% more efficient than their PWM counterparts.

MPPT regulators

In modern times, MPPT regulators have taken over as the most common form of battery charging technology. Along with boasting higher efficiency, MPPT regulators also allow strings of panels to connect in a series, creating higher voltages. This type of connection also results in lower amperage and smaller wire size.

Should I choose a PWM or MPPT regulator?

So, how can you decide what kind of solar controller is right for you and your business?

PWM regulators may be the best choice for you if:

  • You’re looking for a low-cost option
  • You’re running a smaller system
  • System efficiency is not critical, such as with trickle charging
  • Your solar panels have a maximum power voltage of up to 18V, charging a 12V battery

You should consider MPPT controllers if:

  • You’re running a more extensive system
  • Greater efficiency is worthwhile
  • Your solar array voltage is much higher than your battery voltage

Selecting the correct solar controller size

You’ll need to gather some crucial details to help you choose the perfect controller size. These details are:

  • The combined wattage of your solar system
  • The nominal voltage of your solar system
  • The max power voltage of your solar system
  • Your battery charge voltage

With this data on-hand, you’ll need to make a calculation based on whether you’ve chosen a PWM or an MPPT regulator.

For PWM regulators, calculate the combined wattage of your system divided by its max power voltage. The result is your system’s maximum current. Also, record your system’s nominal voltage.

You’ll need a PWM regular that can handle more than your system’s maximum current at your system’s nominal voltage. Your battery voltage must be the same as your system’s nominal voltage.

For MPPT regulators, calculate the combined wattage of your solar system divided by its battery charge voltage. This calculation will give you the system’s maximum current. You’ll also need to know its max power voltage.

You’ll need an MPPT regulator that can handle more than your system’s maximum current. The regulator’s maximum solar input voltage will also need to match your system’s max power voltage.


Choosing the perfect solar controller will depend on your business’s unique needs. With the correct information on-hand, you’ll know the size and type of regulator that will work best for your business.