120W Solar Panel Output (EXPLAINED!)

20W Solar Panel Output

Understanding the output of a 120W solar panel will provide you with information on the amount of electricity it can generate, the types of appliances it can power, and whether it is sufficient for your needs.

After using solar panels for over a year now, I can provide an estimated output of a 120 watt solar panel based on your location.

Looking for an easy solution? Try our free solar panel output calculator to find out the energy output of a 120 watt solar panel.

How are solar panels rated?

The output of a 120W solar panel refers to the amount of electrical power that the panel is capable of generating under ideal conditions. Which includes 1kW/m2 of solar radiation (peak sun hour), 25 degrees Celsius temperature, and 1.5 air mass, also known as STC.

How to calculate solar radiation?

Even though we can't control temperature and air mass, we can measure how much sunlight a location gets using NREL's PV watts calculator.

Step 1: Enter your location (complete address or just city name) and click "GO.". 

How to calculate peak sun hours
Screenshot: Step 1 - Source: NREL Calculator

Step 2: Confirm your location with the help of a map and click "RESULTS." 

How to calculate peak sun hours
Screenshot: Step 2 - Source: NREL Calculator

Step 3: This will show you the average amount of solar radiation your location receives on a monthly basis.

How many peak sun hours in florida?
Screenshot: Solar radiations in Florida, Source: NREL Calculator

1 peak sun hour = 1kW/m2 of solar radiation.

How Much Power Does a 120w Solar Panel Produce?

How Much Power Does a 120w Solar Panel Produce?

On average, a 120-watt solar panel produces about 500-700 watt-hours of power in a day, depending on the number of peak sun hours your solar panel receives.

To calculate the solar panel output, use this formula:

Solar panel output = (Solar Panel rated wattage × Peak sun hours) × 0.8

let's say your location receives an average of 6 peak sun hours daily. The 120 watt solar panel output would be (120 × 6) × 0.8 = 576 watt-hours (Wh).

120 watt solar panel how many amps?

A 12v 120 watt solar panel will produce about 35-50 amps daily.

Amps calculation formula: Amps = Watts ÷ Volts.

Amp (A) is the unit for measuring current. Usually, battery capacity is measured in amp-hours (Ah). Calculating the amps’ output of a 120 watt solar panel will give you an idea of how much power is stored in your battery.

Related post: Solar Panel Amps Calculator (Watts to Amps)

How many volts does a 120 watt solar panel produce?

A 12v 120w solar panel will produce about 18-18.5 volts under ideal conditions (STC).

Volts calculation formula: Voltage = Watts ÷ Amps.

A solar panel will produce a higher voltage when exposed to the sun. So to charge a battery, you need a charge controller. Which will drop the voltage from 18v to 12v to safely charge a 12v battery.

AC vs DC output

Solar panels produce power in direct current (DC), while most household appliances require alternating current (AC).

We use an inverter to convert DC power into AC, but this process is not 100% efficient and can result in a power loss of about 10%.

How many watts does a 120 watt solar panel produce? - chart

Here is a table showing the daily wattage output of a 120-watt solar panel.

Peak Sun Hours120 watt solar panel estimated output
4 peak sun hours380 watt-hours
4.5 peak sun hours430 watt-hours
5 peak sun hours480 watt-hours
5.5 peak sun hours530 watt-hours
6 peak sun hours580 watt-hours
6.5 peak sun hours625 watt-hours
7 peak sun hours670 watt-hours

6 Tips To Improve Solar Panel Output Efficiency

Follow these tips to get the most out of your 120w solar panel.

  1. Keep your solar panels clean.
  2. Avoid installing solar panels in shaded areas.
  3. Use an MPPT charge controller instead of PWM.
  4. Use the right size wiring for your solar system.
  5. Place your solar panels at a right tilt angle.
  6. Avoid getting black colored solar panels, in summer they’ll be less efficient.


How much power is 120 watts?

120 watts are equal to 10 amps @12 volts. You can run a 120 watt appliance for an hour with 120 watt stored power.

How long does it take to charge A car battery with A 120W solar panel?

120 watt solar panel will about 6.2 peak sun hours to fully charge a 12v 50ah car battery from 100% depth of discharge.

Can a 120 watt solar panel charge a 100Ah battery?

Yes, a 120 watt solar can charge a 100ah battery. It will take about 12-14 peak sun hours to fully charge the 100Ah battery from 100% depth of discharge.

I hope this post was helpful to you, if you have any queries or suggestions contact us, 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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