What Size Charge Controller For 250w Solar Panel? Explained!

Don’t know what size charge controller for 250w solar panel? stay with me I’ll explain what size charge controller you need for your 250w solar panel and how to size solar charge controller?

What Size Charge Controller For 250w Solar Panel

What size charge controller/regulator for 250w solar panel?

for a 12v 250 watts solar panel 30A MPPT charge controller is needed & for a 24v 250w solar panel system 15A MPPT charge controller is needed this formula to size solar charge controller (watts/volts = amps + 25%)

i recommend Renogy 24v 30A MPPT Charge controller which can handle up to 800w solar load.

if you wanna know the technical and calculation staff keep reading and ill share the details and some important tips before sizing a charge controller for your solar array.

How Does charge controller work?

first of all, let’s discuss a little bit about how does charge controllers work and why are they needed?

the controller or regulator regulates the DC current from the solar panels to charge the batteries. Solar panels produce power from sunlight so due to weather conditions the solar panels can produce different volts and power at different times of the day.

We install the charge controller between the solar panels and batteries, charge controller adjusts the input power from the solar panels according to the batteries.

Like sometimes a 12v solar panel will produce about 18 volts and if you have a 12v battery the 18 volts can damage it so a charge controller will draw down this with the level of battery’s volts.

How to size solar charge controller?

before sizing a charge controller there are many factors to consider before calculating

Basic knowledge required

  • Check the specs of your solar panel (Optimum volts, amps)
  • Choose a right battery size for according to your solar panel’s voltage

Typically most of the 250w solar panels come in 12v so you’ll need a 12v 160Ah deep cycle battery to store the DC current.

250w solar panel can produce 250 watts of power under ideal sunlight conditions. so calculate the charge controller size using this simple formula.

watts produced by solar panels per hours / volts (battery’s) = amps + 25%

250/12 = 20.8 + 25% = 26 Amps

so a 26A charge controller will be enough for 250w solar panels so round about it to 30A because they are easy to find.

and MPPT charge controller is recommended because they are 30% more efficient than the PWM charge controllers.

How many watts can a 30 amp charge controller handle?

To calculate the maximum watt limit of any charge controller use the ohm’ law formula watts = volts x amps

so to calculate how many watts a 30A charge controller can handle we need to know the voltage output of solar panels

30 x 12 = 360 watts

30 x 24 = 720 watts

make sure to add an extra 25% for safety margins. like if you have a 350-watt solar power system that doesn’t use a 30A charge controller in a 12v connection for it add an extra 25%.

30 amps charge controller can handle 360 watts in 12v solar system and 720 watts in 24v solar system

But every charge controller has its own capacity limit so make sure to check it on their official site. e.g Renogy rover 30A Mppt charge controller can handle up to 400W on 12V and 800W on a 24V system

Read This Before Buying a Charge Controller

here are a few checkpoints before choosing a charge controller for you


Before buying any charge controller from any brand first look for a charge controller at the same voltage as your batteries if you have 24v batteries then go for a 12v charge controller. Most of the charge controllers are designed to cover 12 or 24v solar systems it is worth checking otherwise you’ll limit your output or can damage your solar system.

If you have the same voltage of solar panels and the same voltage of batteries then you can use a PWM charge controller which will still be not much efficient than an MPPT charge controller but if you’re on a budget it’s can be a good deal.

If you have a different voltage of solar panels and different voltage of batteries then definitely go for an MPPT charge controller or else you’ll have a huge loss of power

Future Plans

if you’re sure that you’ll increase your solar panel array in the future then choose a high capacity charge controller because buying an MPPT charge controller isn’t cheaper so your investment in the future, and believe it’s an addiction to increase the solar panel’s power once you step in.

so make sure to try to buy a charge capacity charge controller than what you need right now, you might need it in the future so you’ll have to invest in a new charge controller which will be more costly and it’s also confusing to use two charge controller at a time.

so make yourself relieved and invest in your few bucks for future needs. This is why i also recommend that extra 25%.

Video – How to setup a charge controller

Choose a right wire size

Wiring a wrong-sized wire with a charge controller and batteries can cause a current loss. If you’re using a 12v solar panel it means a large number of amps will pass through the wires so you’ll need a thicker wire. I recommend Renogy 10 AWG wire for a 30A charge controller

Keep the distance between the charge controller and battery as short as you can the longer the distance is the thicker the wire you’ll need. As we know the wires are not 100% efficient. the loss of current also happens in the wires. so use a short wiring system as you can.


Having the right size charge controller is very important to get the maximum power from the solar panels or else you can damage your batteries if you use the wrong charge controller for your solar panels.

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Chris Tsitouris is a renewable energy professional with 10+ years of experience as Director of Engineering at Solar Spectrum, previously working as Project Manager at SunPower and Energy Analyst at the National Renewable Energy Laboratory. As a thought leader, Chris has authored numerous articles and research papers.

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