Use our calculator to find out what size solar panel you need to charge your battery.
Note: If you already have a solar panel size in mind and instead want to estimate how long it will take to charge your battery, check out our solar panel charge time calculator.
Calculator Assumptions
- 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:
- Battery Voltage (V): What is your battery’s voltage?
- 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)
- Battery Type: Is your battery a lead acid or lithium (LiFePO4) battery?
- Battery Depth of Discharge (DoD): What level of discharge is your battery at? 100% means fully discharged and 0% means fully charged.
- Solar Charge Controller Type: Will you be using a PWM or MPPT charge controller?
- 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:
- Battery Voltage (V): 12
- Battery Amp Hours (Ah): 100
- Battery Type: Lithium (LiFePO4)
- Battery Depth of Discharge (DOD): 100%
- Solar Charge Controller Type: MPPT
- Desired Charge Time (in peak sun hours): 16
Turns out, 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 Type | Estimated Solar Panel Size |
|---|---|---|
| 50Ah | Lithium (LiFePO4) | 160 watts |
| 60Ah | Lithium (LiFePO4) | 190 watts |
| 80Ah | Lithium (LiFePO4) | 250 watts |
| 100Ah | Lithium (LiFePO4) | 310 watts |
| 120Ah | Lithium (LiFePO4) | 370 watts |
| 140Ah | Lithium (LiFePO4) | 430 watts |
| 200Ah | Lithium (LiFePO4) | 610 watts |
| 50Ah | Lead acid | 120 watts |
| 60Ah | Lead acid | 140 watts |
| 80Ah | Lead acid | 180 watts |
| 100Ah | Lead acid | 220 watts |
| 120Ah | Lead acid | 260 watts |
| 140Ah | Lead acid | 300 watts |
| 200Ah | Lead acid | 430 watts |
Summary
- You 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 need around 150-300 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 Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 310 watts |
| 10 peak sun hours | MPPT | 160 watts |
| 15 peak sun hours | MPPT | 110 watts |
| 20 peak sun hours | MPPT | 80 watts |
| 25 peak sun hours | MPPT | 70 watts |
| 5 peak sun hours | PWM | 380 watts |
| 10 peak sun hours | PWM | 190 watts |
| 15 peak sun hours | PWM | 130 watts |
| 20 peak sun hours | PWM | 100 watts |
| 25 peak sun hours | PWM | 80 watts |
Summary
- You need around 310 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 need around 380 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 Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 220 watts |
| 10 peak sun hours | MPPT | 100 watts |
| 15 peak sun hours | MPPT | 70 watts |
| 20 peak sun hours | MPPT | 50 watts |
| 25 peak sun hours | MPPT | 40 watts |
| 5 peak sun hours | PWM | 270 watts |
| 10 peak sun hours | PWM | 120 watts |
| 15 peak sun hours | PWM | 80 watts |
| 20 peak sun hours | PWM | 60 watts |
| 25 peak sun hours | PWM | 50 watts |
Summary
- You need around 220 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 need around 270 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 Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 160 watts |
| 10 peak sun hours | MPPT | 80 watts |
| 15 peak sun hours | MPPT | 60 watts |
| 20 peak sun hours | MPPT | 50 watts |
| 25 peak sun hours | MPPT | 40 watts |
| 5 peak sun hours | PWM | 200 watts |
| 10 peak sun hours | PWM | 100 watts |
| 15 peak sun hours | PWM | 70 watts |
| 20 peak sun hours | PWM | 50 watts |
| 25 peak sun hours | PWM | 40 watts |
Summary
- You need a 160 watt solar panel to charge a 12V 50Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You need a 200 watt solar panel 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 Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 120 watts |
| 10 peak sun hours | MPPT | 60 watts |
| 15 peak sun hours | MPPT | 40 watts |
| 20 peak sun hours | MPPT | 30 watts |
| 25 peak sun hours | MPPT | 30 watts |
| 5 peak sun hours | PWM | 140 watts |
| 10 peak sun hours | PWM | 70 watts |
| 15 peak sun hours | PWM | 40 watts |
| 20 peak sun hours | PWM | 30 watts |
| 25 peak sun hours | PWM | 30 watts |
Summary
- You need a 120 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 need a 140 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 Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 370 watts |
| 10 peak sun hours | MPPT | 190 watts |
| 15 peak sun hours | MPPT | 130 watts |
| 20 peak sun hours | MPPT | 100 watts |
| 25 peak sun hours | MPPT | 80 watts |
| 5 peak sun hours | PWM | 460 watts |
| 10 peak sun hours | PWM | 230 watts |
| 15 peak sun hours | PWM | 150 watts |
| 20 peak sun hours | PWM | 120 watts |
| 25 peak sun hours | PWM | 90 watts |
Summary
- You need around 370 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 need around 460 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 Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 260 watts |
| 10 peak sun hours | MPPT | 120 watts |
| 15 peak sun hours | MPPT | 80 watts |
| 20 peak sun hours | MPPT | 60 watts |
| 25 peak sun hours | MPPT | 50 watts |
| 5 peak sun hours | PWM | 330 watts |
| 10 peak sun hours | PWM | 150 watts |
| 15 peak sun hours | PWM | 100 watts |
| 20 peak sun hours | PWM | 70 watts |
| 25 peak sun hours | PWM | 60 watts |
Summary
- You need around 260 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 need around 330 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 140Ah Battery?
12V 140Ah Lithium Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 430 watts |
| 10 peak sun hours | MPPT | 210 watts |
| 15 peak sun hours | MPPT | 150 watts |
| 20 peak sun hours | MPPT | 110 watts |
| 25 peak sun hours | MPPT | 90 watts |
| 5 peak sun hours | PWM | 530 watts |
| 10 peak sun hours | PWM | 270 watts |
| 15 peak sun hours | PWM | 180 watts |
| 20 peak sun hours | PWM | 140 watts |
| 25 peak sun hours | PWM | 110 watts |
Summary
- You need around 430 watts of solar panels to charge a 12V 140Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You need around 530 watts of solar panels to charge a 12V 140Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.
12V 140Ah Lead Acid Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 300 watts |
| 10 peak sun hours | MPPT | 140 watts |
| 15 peak sun hours | MPPT | 90 watts |
| 20 peak sun hours | MPPT | 70 watts |
| 25 peak sun hours | MPPT | 60 watts |
| 5 peak sun hours | PWM | 380 watts |
| 10 peak sun hours | PWM | 170 watts |
| 15 peak sun hours | PWM | 110 watts |
| 20 peak sun hours | PWM | 80 watts |
| 25 peak sun hours | PWM | 70 watts |
Summary
- You need around 300 watts of solar panels to charge a 12V 140Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You need around 380 watts of solar panels to charge a 12V 140Ah 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 Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 610 watts |
| 10 peak sun hours | MPPT | 300 watts |
| 15 peak sun hours | MPPT | 200 watts |
| 20 peak sun hours | MPPT | 150 watts |
| 25 peak sun hours | MPPT | 130 watts |
| 5 peak sun hours | PWM | 760 watts |
| 10 peak sun hours | PWM | 380 watts |
| 15 peak sun hours | PWM | 250 watts |
| 20 peak sun hours | PWM | 190 watts |
| 25 peak sun hours | PWM | 150 watts |
Summary
- You need around 610 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 need around 760 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 Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 430 watts |
| 10 peak sun hours | MPPT | 200 watts |
| 15 peak sun hours | MPPT | 130 watts |
| 20 peak sun hours | MPPT | 100 watts |
| 25 peak sun hours | MPPT | 80 watts |
| 5 peak sun hours | PWM | 540 watts |
| 10 peak sun hours | PWM | 240 watts |
| 15 peak sun hours | PWM | 160 watts |
| 20 peak sun hours | PWM | 120 watts |
| 25 peak sun hours | PWM | 90 watts |
Summary
- You need around 430 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 need around 520 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 wire 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 Type | Estimated Solar Panel Size |
|---|---|---|
| 50Ah | Lithium (LiFePO4) | 310 watts |
| 100Ah | Lithium (LiFePO4) | 610 watts |
| 200Ah | Lithium (LiFePO4) | 1200 watts |
| 50Ah | Lead acid | 220 watts |
| 100Ah | Lead acid | 430 watts |
| 200Ah | Lead acid | 850 watts |
Summary
- You need around 300-600 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 need around 200-450 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?
Peak sun hours (also called “peak sunlight hours” or simply “sun 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 from 9am to 10am the sun shines with an average intensity of 400 W/m2, then that would be equal to 0.4 peak sun hours. Then if from 1pm to 2pm 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.
Plus, we can use historical data to predict how many peak sun hours a location will get on an average day. These predictions help when picking what size solar panel or system to use.
