Solar Panel Size Calculator: What Size Panel Do I Need?

What size solar panel do you need to charge your battery? Enter your battery specs, solar charge controller type and desired charge time into our solar panel size calculator to find out:

Solar Panel Size Calculator

Error: Enter a valid voltage
Error: Enter a valid battery capacity
Error: Select a battery type
Error: Select a charge controller type
Error: Enter a valid number of hours
Estimated solar panel size to charge your battery in peak sun hours:
watts
Warning: We estimate that a solar power system with these parameters would have a maximum charge current of . Many battery manufacturers recommend a maximum charge current of for lead acid batteries with this capacity. To maximize your battery’s lifespan, consider using a smaller solar panel or a bigger battery. Or increase your desired charge time.
Warning: We estimate that a solar power system with these parameters would have a maximum charge current of . Many battery manufacturers recommend a maximum charge current of for lithium iron phosphate batteries with this capacity. To maximize your battery’s lifespan, consider using a smaller solar panel or a bigger battery. Or increase your desired charge time.
Error: We estimate that it is impossible to charge your battery this quickly. The typical absorption time for batteries is around hours, which is greater than (or equal to) your desired charge time. Increase your desired charge time and try again.

Note: If you already have a solar panel size in mind and want to estimate how long it will take to charge your battery, check out our solar panel charge time calculator.

Calculator Assumptions

  • Lead acid depth of discharge: 50% DoD
  • Lithium (LiFePO4) depth of discharge: 100% DoD
  • The solar charge controller is the only load connected to the battery

What Size Solar Panel Do I Need?

To find out what size solar panel you need to charge your battery, you’ll need to enter the following info into our solar panel size calculator at the top of this page:

  1. Battery Voltage (V): What is your battery’s voltage?
  2. Battery Amp Hours (Ah): What is your battery’s capacity in amp hours? (If you only know its capacity in watt hours, first convert watt hours to amp hours)
  3. Battery Type: Is your battery a lead acid or lithium (LiFePO4) battery?
  4. Solar Charge Controller Type: Will you be using a PWM or MPPT charge controller?
  5. Desired Charge Time (in peak sun hours): How quickly do you want your solar panel to charge your battery, in peak sun hours?

Once you’ve entered the above info, click “Calculate Solar Panel Size” to get an estimate of what size panel you need to charge your battery at your desired speed.

Example

Let’s say you have a 12V 100Ah LiFePO4 battery and an MPPT charge controller in your RV. You want a solar panel that will charge your battery in 16 peak sun hours.

To find out what size solar panel you need, you’d simply plug the following into the calculator:

  1. Battery Voltage (V): 12
  2. Battery Amp Hours (Ah): 100
  3. Battery Type: Lithium (LiFePO4)
  4. Solar Charge Controller Type: MPPT
  5. Desired Charge Time (in peak sun hours): 16

When you do, you get the following result:

You need a 100 watt solar panel to charge a 12V 100Ah lithium battery in 16 peak sun hours with an MPPT charge controller.

What Size Solar Panel to Charge 12V Battery?

12 volt batteries are the most common voltage I see people using in their solar power setups. Here is a chart showing what size solar panel you need to charge 12V batteries of various capacities in 5 peak sun hours with an MPPT charge controller.

Battery Amp Hours (Ah)Battery TypeEst. Solar Panel Size
50AhLithium (LiFePO4)170 watts
60AhLithium (LiFePO4)210 watts
80AhLithium (LiFePO4)270 watts
100AhLithium (LiFePO4)340 watts
120AhLithium (LiFePO4)410 watts
200AhLithium (LiFePO4)680 watts
50AhLead acid150 watts
60AhLead acid180 watts
80AhLead acid230 watts
100AhLead acid290 watts
120AhLead acid350 watts
200AhLead acid570 watts

Summary

  • You would need around 200-400 watts of solar panels to charge many common 12V lithium battery sizes from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need around 150-350 watts of solar panels to charge many common 12V lead acid battery sizes from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.

Full article: What Size Solar Panel to Charge 12V Battery?

What Size Solar Panel to Charge 100Ah Battery?

12V 100Ah batteries are some of the most common in solar power systems. Here are some tables with the solar panel sizes you need to charge them at various speeds:

12V 100Ah Lithium Battery

Charge TimeCharge Controller TypeEst. Solar Panel Size
5 peak sun hoursMPPT340 watts
10 peak sun hoursMPPT170 watts
15 peak sun hoursMPPT110 watts
20 peak sun hoursMPPT80 watts
25 peak sun hoursMPPT70 watts
5 peak sun hoursPWM430 watts
10 peak sun hoursPWM210 watts
15 peak sun hoursPWM140 watts
20 peak sun hoursPWM100 watts
25 peak sun hoursPWM80 watts

Summary

  • You would need around 340 watts of solar panels to charge a 12V 100Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need around 430 watts of solar panels to charge a 12V 100Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.

Full article: What Size Solar Panel to Charge 100Ah Battery?

12V 100Ah Lead Acid Battery

Charge TimeCharge Controller TypeEst. Solar Panel Size
5 peak sun hoursMPPT290 watts
10 peak sun hoursMPPT110 watts
15 peak sun hoursMPPT70 watts
20 peak sun hoursMPPT50 watts
25 peak sun hoursMPPT40 watts
5 peak sun hoursPWM360 watts
10 peak sun hoursPWM140 watts
15 peak sun hoursPWM90 watts
20 peak sun hoursPWM70 watts
25 peak sun hoursPWM50 watts

Summary

  • You would need around 290 watts of solar panels to charge a 12V 100Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need around 360 watts of solar panels to charge a 12V 100Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.

What Size Solar Panel to Charge 50Ah Battery?

The 12V 50Ah battery is another common battery size in solar power systems. Some car batteries are also 50Ah.

Because lead acid batteries only have 50% usable capacity, a 50Ah LiFePO4 battery has as much usable capacity as a 100Ah lead acid battery.

12V 50Ah Lithium Battery

Charge TimeCharge Controller TypeEst. Solar Panel Size
5 peak sun hoursMPPT170 watts
10 peak sun hoursMPPT90 watts
15 peak sun hoursMPPT60 watts
20 peak sun hoursMPPT40 watts
25 peak sun hoursMPPT40 watts
5 peak sun hoursPWM220 watts
10 peak sun hoursPWM110 watts
15 peak sun hoursPWM70 watts
20 peak sun hoursPWM50 watts
25 peak sun hoursPWM40 watts

Summary

  • You would need around 170 watts of solar panels to charge a 12V 50Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need around 220 watts of solar panels to charge a 12V 50Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.

12V 50Ah Lead Acid Battery

Charge TimeCharge Controller TypeEst. Solar Panel Size
5 peak sun hoursMPPT150 watts
10 peak sun hoursMPPT60 watts
15 peak sun hoursMPPT40 watts
20 peak sun hoursMPPT30 watts
25 peak sun hoursMPPT20 watts
5 peak sun hoursPWM180 watts
10 peak sun hoursPWM70 watts
15 peak sun hoursPWM50 watts
20 peak sun hoursPWM40 watts
25 peak sun hoursPWM30 watts

Summary

  • You would need a 150 watt solar panel to charge a 12V 50Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need a 180 watt solar panel to charge a 12V 50Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.

What Size Solar Panel to Charge 120Ah Battery?

12V 120Ah Lithium Battery

Charge TimeCharge Controller TypeEst. Solar Panel Size
5 peak sun hoursMPPT410 watts
10 peak sun hoursMPPT200 watts
15 peak sun hoursMPPT130 watts
20 peak sun hoursMPPT100 watts
25 peak sun hoursMPPT80 watts
5 peak sun hoursPWM520 watts
10 peak sun hoursPWM250 watts
15 peak sun hoursPWM160 watts
20 peak sun hoursPWM120 watts
25 peak sun hoursPWM100 watts

Summary

  • You would need around 410 watts of solar panels to charge a 12V 120Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need around 520 watts of solar panels to charge a 12V 120Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.

12V 120Ah Lead Acid Battery

Charge TimeCharge Controller TypeEst. Solar Panel Size
5 peak sun hoursMPPT350 watts
10 peak sun hoursMPPT130 watts
15 peak sun hoursMPPT90 watts
20 peak sun hoursMPPT60 watts
25 peak sun hoursMPPT50 watts
5 peak sun hoursPWM440 watts
10 peak sun hoursPWM170 watts
15 peak sun hoursPWM110 watts
20 peak sun hoursPWM80 watts
25 peak sun hoursPWM60 watts

Summary

  • You would need around 350 watts of solar panels to charge a 12V 120Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need around 440 watts of solar panels to charge a 12V 120Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.

What Size Solar Panel to Charge 200Ah Battery?

Because lead acid batteries only have 50% usable capacity, 200Ah lead acid batteries have as much usable capacity as 100Ah lithium iron phosphate batteries.

12V 200Ah Lithium Battery

Charge TimeCharge Controller TypeEst. Solar Panel Size
5 peak sun hoursMPPT680 watts
10 peak sun hoursMPPT320 watts
15 peak sun hoursMPPT220 watts
20 peak sun hoursMPPT160 watts
25 peak sun hoursMPPT130 watts
5 peak sun hoursPWM860 watts
10 peak sun hoursPWM410 watts
15 peak sun hoursPWM270 watts
20 peak sun hoursPWM200 watts
25 peak sun hoursPWM160 watts

Summary

  • You would need around 680 watts of solar panels to charge a 12V 200Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need around 860 watts of solar panels to charge a 12V 200Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.

12V 200Ah Lead Acid Battery

Charge TimeCharge Controller TypeEst. Solar Panel Size
5 peak sun hoursMPPT570 watts
10 peak sun hoursMPPT220 watts
15 peak sun hoursMPPT140 watts
20 peak sun hoursMPPT100 watts
25 peak sun hoursMPPT80 watts
5 peak sun hoursPWM720 watts
10 peak sun hoursPWM280 watts
15 peak sun hoursPWM170 watts
20 peak sun hoursPWM130 watts
25 peak sun hoursPWM100 watts

Summary

  • You would need around 570 watts of solar panels to charge a 12V 200Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need around 720 watts of solar panels to charge a 12V 200Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.

What Size Solar Panel to Charge 24V Battery?

24 volt batteries aren’t as easy to find as 12 volt batteries, but you can connect two 12V batteries in series to create a 24V battery bank. Some battery brands sell twin packs of 12V batteries for just this reason.

Here is a chart showing what size solar panel you need to charge 24V batteries of various capacities in 5 peak sun hours with an MPPT charge controller.

Battery Amp Hours (Ah)Battery TypeEst. Solar Panel Size
50AhLithium (LiFePO4)340 watts
100AhLithium (LiFePO4)680 watts
200AhLithium (LiFePO4)1350 watts
50AhLead acid290 watts
100AhLead acid570 watts
200AhLead acid1140 watts

Summary

  • You would need around 350-700 watts of solar panels to charge common 24V lithium battery sizes from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
  • You would need around 300-600 watts of solar panels to charge common 24V lead acid battery sizes from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.

What Are Peak Sun Hours?

Note: Use our peak sun hours calculator to find out how many peak sun hours your location gets.

Peak sun hours (aka peak sunlight hours) are a way to measure how much sunlight you can expect to receive at a specific location.

A peak sun hour is defined as one hour in which the intensity of sunlight (solar irradiance) averages 1,000 watts per square meter.

So we can write it as:

1 peak sun hour = 1,000 W/m2 of sunlight per hour.

Because 1,000 watts is equal to 1 kilowatt, we can also write it as:

1 peak sun hour = 1 kW/m2 of sunlight per hour.

Peak hours are NOT the hours from sunrise to sunset. They are also NOT the number of hours the sun shines in a day. They are instead a measure of the total amount of sunlight a location gets in a day.

If one day at 9am the sun shines with an average intensity of 400 W/m2, then that would be equal to 0.4 peak sun hours. Then if at 1pm that same day the sun shines with an average intensity of 1,050 W/m2, that would be equal to 1.05 peak sun hours.

For example, let’s say you live in Nevada, and on a clear spring day the sun shines with the following intensities by hour:

  • 6am: 50 W/m2 = 0.05 peak sun hours
  • 7am: 100 W/m2 = 0.1 peak sun hours
  • 8am: 200 W/m2 = 0.2 peak sun hours
  • 9am: 400 W/m2 = 0.4 peak sun hours
  • 10am: 700 W/m2 = 0.7 peak sun hours
  • 11am: 950 W/m2 = 0.95 peak sun hours
  • 12pm: 1,000 W/m2 = 1 peak sun hour
  • 1pm: 1,000 W/m2 = 1 peak sun hour
  • 2pm: 950 W/m2 = 0.95 peak sun hours
  • 3pm: 700 W/m2 = 0.7 peak sun hours
  • 4pm: 400 W/m2 = 0.4 peak sun hours
  • 5pm: 200 W/m2 = 0.2 peak sun hours
  • 6pm: 100 W/m2 = 0.1 peak sun hours
  • 7pm: 50 W/m2 = 0.05 peak sun hours

To measure how much sun you got that day, you’d sum up the intensity of sunlight for each hour in peak sun hours.

In this case, you would have received 6.8 peak sun hours that day.

Why Use Peak Sun Hours?

Sunlight varies in intensity by location and time of day. The sun shines more intensely at 1pm in Arizona than it does at 8AM in Alaska.

So if we were just to measure the length of time sun shines on a solar panel, it wouldn’t give us a very clear idea of how much energy that solar panel generated during that time. We need to know how intense that sunlight was.

By measuring the sunlight in peak sun hours, we can quantify how much sunlight a solar panel receives. Then we can use that number to better estimate how much solar energy was generated during that time.

More Solar Calculators

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Alex Beale
Alex Beale
Hi, I'm Alex. I started Footprint Hero to help people reduce their environmental impact. My current obsession is DIY solar power projects, which I've been building since 2020.