Solar Panel Size Calculator helps you determine optimal solar panel system for your off-grid needs by calculating required wattage based on your battery specifications, charge controller type, and peak sunlight conditions.
Simply input your Battery Capacity (Ah), Voltage (V), type, and desired recharge time, and the tool will recommend ideal solar panel size and charge controller current for efficient energy production.
Whether you’re setting up small cabin system or larger off-grid installation, this calculator provides accurate estimates to ensure your solar setup meets your power requirements.
Solar Panel Size Calculator
(Optional: If left blank, we’ll use a default value of 50% DoD for lead acid batteries and 100% DoD for lithium batteries.)
(You can use a peak sun hours calculator to find out how many peak sun hours your location gets per day.)
Solar Panel Size Calculator is top-rated tool designed to simplify off-grid solar system planning by accurately determining the ideal solar panel wattage for your energy needs. It ranks highly among DIY solar enthusiasts and professionals for its precise calculations based on battery capacity, voltage, type, and peak sunlight conditions.
Users appreciate its ability to factor in Depth of Discharge (DoD) and charge controller efficiency, ensuring reliable recommendations for both PWM and MPPT systems. Its intuitive interface and detailed results make it trusted resource for optimizing solar power setups, whether for RVs, cabins, or full off-grid homes.
By delivering customized panel size and charge controller specifications, this calculator helps maximize energy efficiency while minimizing guesswork, making it go to solution for solar planning.
How to Use the Solar Panel Size Calculator
Figuring out the right solar panel size for your off-grid setup is easier than you think just plug in your numbers, and this tool does the heavy lifting. Here’s how to use it:
1. Enter your battery’s Amp hour (Ah) rating
This tells the calculator how much energy your battery can store.
2. Select your battery voltage (e 12V, 24V, etc.)
This helps match your system’s power needs accurately.
3. Choose your battery type
Whether it’s lithium, lead-acid, or another type—this adjusts the efficiency settings.
4. Pick your charge controller type (PWM or MPPT)
This affects how effectively your solar panels charge your battery.
5. Enter your battery’s depth of discharge (DoD)
For example, 50% for lead-acid. If you’re not sure, just leave it blank—we’ll choose the best default.
6. Add your local peak sun hours
This tells us how much sunlight your area gets (you can look it up online if needed).
Once you’ve filled in all the details, click Calculate. In just seconds, you’ll get:
- Ideal solar panel size (in watts)
- Recommended charge controller current (in amps)
No technical jargon just simple, useful results to help power your off-grid setup with confidence.
What Size Solar Panel Do I Need?
Suppose your RV has an MPPT charge controller and a 12V 100Ah LiFePO4 battery. A solar panel that can charge your battery during 16 of the sun’s strongest hours is what you desire.
You would only enter the following information into the calculator to get the size of solar panel you require:
- Voltage of Battery: 12V
- Hours of Battery Amp (Ah): 100
- Type of Battery: Lithium (LiFePO4)
- Depth of Discharge (DOD) of Battery: 100%
- Controller for Solar Charging Type: MPPT
- Desirable Charging Time (during most sunny parts of the day): 16
Perfect solar panel size depends on your battery setup and how fast you want to recharge it. Here’s the simple breakdown:
- Check your battery specs: Note its Amp-hour (Ah) rating and voltage (12V, 24V, etc.)
- Know your battery type: Lithium or lead-acid? This affects charging efficiency
- Consider your location: How many peak sunlight hours you get daily (4-6 hours is typical)
- Decide recharge speed: Faster charging needs bigger panels
For example:
100Ah 12V battery needing 1-day recharge typically requires about 300W of solar
The same battery with 2 days to recharge might only need 150W
Our calculator does the math for you just plug in your numbers for precise recommendation!
It turns out that in order to use an MPPT charge controller to charge a 12V 100Ah lithium battery during 16 peak sun hours, you need 100 watt solar panel.
Pro tip: Always size up by 20-30% to account for cloudy days and system losses.
Which Solar Panel Size Is Best for Charging a 12V Battery?
Most popular voltage I see consumers employing in their solar power installations are 12 volt batteries. Here is chart that illustrates size of solar panels required to use an MPPT charge controller to charge 12V batteries with different capacity during five peak sun hours.
| 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 |
Using an MPPT charge controller, you can charge a variety of typical 12V lithium battery sizes from 100% depth of discharge in five peak sun hours with about 200 400 watts of solar panels.
With an MPPT charge controller, you can charge a variety of typical 12V lead acid battery sizes from 50% depth of drain in five peak sun hours using 150–300 watts of solar panels.
Which Solar Panel Size Is Best for Charging a 100Ah Battery?
Among most used batteries for solar power systems are 12V 100Ah batteries. The solar panel sizes you need to charge them at different speeds are listed in the following tables:
100Ah Lithium Battery 12V
| 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 |
To charge a 12V 100Ah lithium battery from 100% depth of discharge in five peak sun hours using an MPPT charge controller, around 310 watts of solar panels are required.
To charge a 12V 100Ah lithium battery from 100% depth of drain in five peak sun hours using a PWM charge controller, around 380 watts of solar panels are required.
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 |
To charge 12V 100Ah lead acid battery from 50% discharge in five peak sun hours using an MPPT charge controller, around 220 watts of solar panels are required.
Using PWM charge controller, you can charge 12V 100Ah lead acid battery from 50% discharge in five peak sun hours using about 270 watts of solar panels.
Which Solar Panel Size Is Best for Charging 50Ah Battery?
Another typical battery size in solar power systems is the 12V 50Ah battery. There are also 50Ah automobile batteries.
50Ah LiFePO4 battery has as much useful capacity as a 100Ah lead acid battery because lead acid batteries only have 50% useable capacity.
50Ah, 12V 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 |
To charge a 12V 50Ah lithium battery from 100% depth of drain in five peak sun hours using an MPPT charge controller, you’ll need 160 watt solar panel.
200 watt solar panel and PWM charge controller are required to fully charge a 12V 50Ah lithium battery during five hours of the sun’s hottest hours.
Lead acid battery, 12V, 50Ah
| 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 |
To charge 12V 50Ah lead acid battery from 50% discharge in five peak sun hours using an MPPT charge controller, you’ll need a 120 watt solar panel.
To use a PWM charge controller to charge a 12V 50Ah lead acid battery from 50% discharge in five peak sun hours, you will require a 140 watt solar panel.
Which Solar Panel Size Is Best for Charging a 120Ah Battery?
120Ah Lithium Battery at 12V
| 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 |
To charge 12V 120Ah lithium battery from 100% depth of drain in five peak sun hours using an MPPT charge controller, around 370 watts of solar panels are required.
Using PWM charge controller, 12V 120Ah lithium battery can be charged from 100% discharge in five peak sun hours using about 460 watts of solar panels.
Lead Acid Battery, 12V, 120Ah
| 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 |
To charge 12V 120Ah lead acid battery from 50% discharge in five peak sun hours using an MPPT charge controller, you’ll need about 260 watts of solar panels.
For 12V 120Ah lead acid battery to be charged from 50% discharge in five peak sun hours using PWM charge controller, about 330 watts of solar panels are required.
Which Solar Panel Size Is Best for Charging 140Ah Battery?
140Ah Lithium Battery at 12V
| 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 |
Using an MPPT charge controller, you can charge a 12V 140Ah lithium battery from 100% depth of drain in five peak sun hours with about 430 watts of solar panels.
To charge a 12V 140Ah lithium battery from 100% drain in five peak sun hours using a PWM charge controller, you’ll need about 530 watts of solar panels.
Lead acid battery, 12V, 140Ah
| 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 |
To charge a 12V 140Ah lead acid battery from 50% discharge in five peak sun hours using an MPPT charge controller, you’ll need about 300 watts of solar panels.
Using a PWM charge controller, you can charge a 12V 140Ah lead acid battery from 50% discharge in five peak sun hours using about 380 watts of solar panels.
Which Solar Panel Size Is Best for Charging 200Ah Battery?
200Ah lead acid batteries have the same usable capacity as 100Ah lithium iron phosphate batteries since lead acid batteries only have 50% usable capacity.
Lithium battery with 12V and 200Ah
| 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 |
To charge 12V 200Ah lithium battery from 100% depth of discharge in five peak sun hours using an MPPT charge controller, around 610 watts of solar panels are required.
To charge 12V 200Ah lithium battery from 100% depth of drain in five peak sun hours using a PWM charge controller, around 760 watts of solar panels are required.
Lead acid battery, 12V, 200Ah
| 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 |
To charge a 12V 200Ah lead acid battery from 50% discharge in five peak sun hours using an MPPT charge controller, around 430 watts of solar panels are required.
To charge a 12V 200Ah lead acid battery from 50% discharge in five peak sun hours using a PWM charge controller, around 520 watts of solar panels are required.
Which Solar Panel Size Is Best for Charging 24V Battery?
Although 24 volt batteries are more difficult to locate than 12 volt ones, 24 volt battery bank can be made by connecting two 12 volt batteries in series. For this reason alone, several battery manufacturers offer dual packs of 12V batteries.
This table illustrates the size of solar panels required to use an MPPT charge controller to charge 24V batteries with different capacity during five peak sun hours.
| 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 |
Using an MPPT charge controller, you can charge typical 24V lithium battery sizes from 100% depth of discharge in five peak sun hours with about 300 600 watts of solar panels.
Using an MPPT charge controller, you can charge typical 24V lead acid battery sizes from 50% depth of drain in five peak sun hours with about 200 450 watts of solar panels.
Peak Sun Hours: What Are They?
Peak sun hours, sometimes referred to as “peak sunlight hours” or just “sun hours,” are a means to gauge how much sunshine is likely to fall at a given spot.
An hour when solar irradiance, or the intensity of sunshine, averages 1,000 watts per square meter is known as a peak sun hour.
So we can write it as:
1,000 W/m2 of sunshine per hour is equal to one peak sun hour.
We can alternatively put it as follows since 1,000 watts is equivalent to one kilowatt:
One kW/m2 of sunlight per hour is equal to one peak sun hour.
Sunrise to sunset are not considered peak hours. Additionally, they do not represent the number of hours that the sun shines in day. Rather, they serve as a gauge of how much sunlight a place receives overall over the day.
It would be equivalent to 0.4 peak solar hours if the sun shone with an average intensity of 400 W/m2 on a single day between 9 and 10 am. In such case, 1.05 peak sun hours would occur if the sun shone with an average intensity of 1,050 W/m2 from 1 to 2 p.m. the same day.
For instance, suppose you live in Nevada and the sun is shining with the following hourly intensities on clear spring day:
- 50 W/m2 = 0.05 peak sun hours at 6 a.m.
- 100 W/m2 = 0.1 peak sun hours at 7 a.m.
- 200 W/m2 = 0.2 peak sun hours at 8 a.m.
- 400 W/m2 = 0.4 peak solar hours at 9 a.m.
- 700 W/m2 = 0.7 peak solar hours at 10 a.m.
- 950 W/m2 = 0.95 peak solar hours at 11 a.m.
- 1,000 W/m2 = 1 peak solar hour at 12 p.m.
- 1pm: 1 peak solar hour (1,000 W/m2)
- 950 W/m2 = 0.95 peak solar hours at 2 p.m.
- 700 W/m2 = 0.7 peak solar hours at 3 p.m.
- 400 W/m2 = 0.4 peak solar hours at 4 p.m.
- 200 W/m2 = 0.2 peak solar hours at 5 p.m.
- 100 W/m2 = 0.1 peak solar hours at 6 p.m.
- 50 W/m2 = 0.05 peak solar hours at 7 p.m.
If the sun shone with an average intensity of 400 W/m2 on a single day between 9 and 10 am, that would be equal to 0.4 peak solar hours. In this scenario, if the sun shone from 1 to 2 p.m. on the same day with an average intensity of 1,050 W/m2, 1.05 peak sun hours would occur.
Assume, for example, that on a bright spring day in Nevada, the sun is shining with the following hourly intensities:
Why Use the Best Sunlight Hours?
The intensity of sunlight differs depending on the time of day and the location. In Arizona, the sun is brighter at 1pm than it is in Alaska at 8AM.
Therefore, it would be difficult to determine how much energy a solar panel produced in a given period of time if we were only to measure the amount of time the sun shone on it. We must know the strength of that sun.
We can measure the amount of sunshine that a solar panel receives by taking measurements during the hottest parts of the day. The amount of solar energy created during that period can then be more accurately estimated using that figure.
Additionally, we can forecast how many peak solar hours a place will receive on a typical day by using historical data. When choosing the appropriate solar panel or system size, these forecasts are helpful.