What Size Charge Controller For 500w Solar Panel? Explained!

There are many different factors to consider before sizing a charge controller size for your solar panels. a simple small mistake can lower the output of your solar panels or even can damage the charge controller or batteries

so, in this blog, I’ll guide you to choose the right size charge controller for your 500w solar panel system.

for 24v 500w solar panels, will need a 30A MPPT charge controller to power the batteries from solar panels (Watts/volts = amps + 25%) the extra 25% due to safety reasons

i recommend this Renogy rover 30A mppt charge controller which will work fine with 12v and 24v solar arrays.

i have 500 watts of the solar power system in my house for the emergency case and we run our few appliances on it just to cut the electricity bill. I’m also using two 200w Renogy portable solar panels for my RV and with them, i use a portable power station.

so now I’ll share a complete guide about sizing charge controllers for your solar panels according to your need. so if you have a 1000w, or 2000w solar power system you can use these calculation methods to size your charge controller for solar panels

Why do you need a charge controller for your 500w solar panels?

The main purpose of installing a charge controller (Between solar panels and batteries) is to increase the lifespan of batteries and prevent them from damaged.

Solar panels produce DC current from the sunlight and with the help of a charge controller we store that energy into batteries or power banks for later use. Due to the sunlight intensity, the DC current from solar panels fluctuates so if you’ll connect your solar panels directly with the batteries it can damage the battery’s overall health or can also use make them useless.

Charge controller sizing guide

use this simple formula to calculate the size of the charge controller for your solar panel’s watts/volts = amps + 25%

for a 500w solar panel system, you’ll require 24v batteries, 12v batteries can work fine up to 300W solar panels.

so a 500w solar panel can produce about 500 watts of power per hour under ideal sunlight conditions but your 24v 500w solar panel will produce higher volts due to the intensity or temperature so to cover these numbers you need a charge controller

for 24v solar panels you’ll also need a 24v battery, so now let’s add up those numbers

500/24 = 20.8 + 25% = 26A

typically a 20A charge controller can handle 24v 500w solar panels but for safety factors, we add 25% extra which will make it 26A and there are 30A charge controllers available so you’ll need a 30A MPPT charge controller

Most of the experts advise adding an extra 25% for a few reasons first of all you shouldn’t be using an electronic at its high capacity continuously which can decrease its lifespan of it and secondly it gives you a little bit of flexibility for more safety

now, why does MPPT charge controller, and what it does. let’s discuss it

PWM vs MPPT – which one is best for you?

PWM – stands for Pulse Width Modulation charge controller will draw down the voltage of solar panels to match with the battery voltage which will cause a loss in power.

For example, if your solar panels are producing 40 volts and 12.5 amps which 24v 500w solar panels can produce during peak sun hours a PWM charge controller will draw down the voltage to 24V to charge the 24v battery and amps will stay the same which will cause the loss in power.

Note: batteries can take more voltage than recommended like a 24v battery would be able to handle about 28-30 volts

so the PWM charge controller will draw 28-30 volts with 12.5 amps. as we know the formula to calculate the power volts x amps = watts so 40 x 12.5 = 500 watts and if you have a PWM charge controller 30 x 12.5 = 375 watts a loss of 125 watts.

MPPT – Maximum Power Point Tracking charge controller draws the power at its maximum power by matching its internal resistance to the solar panel’s Characteristic Resistance.

For Example, if your 500w solar panels are producing 40 volts at peak sun hours the MPPT charge controller will draw maximum volts which a 24v battery would be able to handle like 30 volts as i have discussed, and will increase the amps instead. which makes them more efficient then the PWM charge controllers

I recommend watching this video for more details and watching by yourself you’ll see how massive a difference an MPPT charge controller can create.

MPPT vs PWM Pros & Cons – Video

Some common mistakes to avoid

Check charge controller upper voltage limit every charge controller has its upper voltage limit so make sure to check it before making a purchase or it can create damage to your solar system e.g Renogy 30A MPPT charge controller Can support up to 400W on 12V or 800W on 24V systems which I recommended

just DC appliances should be connected to the charge controller don’t connect AC appliances directly to the charge controller


Pairing the right size and type of charge controller with your solar panels is very essential to get the maximum output from your solar panels to make them last longer and prevent any damage. Use these tips to calculate the charge controller size for your solar panels.

I hope this article was helpful to you if you have any queries feel free to ask at contact@dotwatts.com. Thank you!

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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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