300 watt Solar Panel: Output (Amps, volts), & What Can It Run?

In this post, you’ll learn how much power you can expect from a 300-watt solar panel in the real-life world and what you can power with it. 

I did an experiment with my 200-watt solar panel, which I’m gonna use as a reference.

How Much Power Does A 300 Watt Solar Panel Produce?

Need a simple solution? Use our solar panel output calculator to find out how much energy a 300 watt solar panel will produce on average per day in your city. 

Solar panels are designed to produce their rated wattage rating under standard test conditions (1kW/m2 solar irradiance, 25oC temperature, and 1.5 air mass). 

But in real world conditions, on average, you’d receive about 80% of rated power output from your solar panel during peak sun hour.

Peak sun hour is an hour in the day when the solar radiation reaches an average of 1000 watts/meter2 (1 peak sun hour = 1kW/m2 solar radiation).

How to calculate peak sun hours for your location? Visit PVWatts Calculator by NREL. Enter your address and click GO >>. Make sure that calculator has picked up the right location with the help of a map, if it does, click “RESULTS”.

Florida city peak sun hour data: Source - NREL calculator

Full article: Peak Sun Hours: Explanation, Importance, How To Calculate?

Watts, Watt-hours

On average, a 300 watt solar panel will produce about 240 watt-hours during peak sun hour (1kW/m2 of solar radiation hitting the surface of the solar panel). And 1.2kW energy per day, considering 5 peak sun hours (5kW/m2 solar radiation).

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

300-watt Solar Panel How Many Amps and volts?

12v 300 watt solar panel will produce about 16.2 amps and 18.5 volts under ideal conditions (STC).

That is why you need a 30A charge controller with 300 watt solar panel, which will regulate the voltage output of the solar panel to safely charge a 12 or 24-volt battery. 

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

300 watt Solar Panel Output chart

Here’s a chart about 300-watt solar panels' total energy output with different peak sun hours. 

Peak Sun Hours300 watt solar panel estimated output
4 peak sun hours960 watt-hours
4.5 peak sun hours1.08 kilowatt-hours
5 peak sun hours1.2 kilowatt-hours
5.5 peak sun hours1.3 kilowatt-hours
6 peak sun hours1.4 kilowatt-hours
6.5 peak sun hours1.5 kilowatt-hours
7 peak sun hours1.6 kilowatt-hours

Note: 1kWh = 1000 watts.

DC To AC Power Conversion loss 

As we have discussed how much DC power you can receive from your 300-watt solar panel, to run most of the household appliances you need AC power. 

To convert DC into AC we use an inverter, and most of the inverters are about 90% efficient. So there will be a 10% power loss when converting DC into AC.

For Example

Here in Florida, I would receive about 1.4kWh of DC power output from a 300-watt solar panel in July. 

300 * 0.8 = 240 watts
240 * 6 = 1440Wh or 1.44kWh (1kw = 1000 watt)

Now let’s convert the DC into AC while using a 90% efficient inverter.

1440 * 0.9 = 1296 or 1.3kWh 

You can expect 1.3kWh AC electricity output from a 300-watt solar panel per day, considering 6 hours of peak sunlight.

Related Post: Solar DC Watts To AC Watts Calculator & Formula

What Can a 300-watt Solar Panel Run? 

A 300-watt solar panel can directly run a constant load of 240 DC or 210 AC. That means you can run a medium size new technology kitchen fridge, TV, Fan, Computer/laptop, LED light, etc. But with the help of a battery, you can run 1300 watts of AC load for an hour with a 300-watt solar panel.

If you follow these 2 rules, you can run any appliance with a 300-watt solar panel. 

Rule #1 

If your battery has reached its depth of discharge limit or doesn’t have any power, then your load output AC load should not exceed the output of your solar panel’s AC watts. 

Rule #2 

If you have stored the power produced by your solar panel in batteries, do not discharge your batteries at a higher rate. 

This you’d damage your battery cells, As a result, it will decrease the battery lifespan. 

Make sure to check your battery’s specs sheet and look for the maximum discharge rate or C-ratings.

Related post: Battery Charge And Discharge Rate Calculator 

Can A 300 Watt Solar Panel Run a Refrigerator

A 300-watt solar panel can produce enough energy to run a large size kitchen (15 - 22 cu. ft.) between 10-20 hours.

I have discussed this topic in detail, click here to read for more in-depth information. 

300-watt Solar Panel: FAQs

How many batteries do i need for a 300-watt solar panel?

For a 300-watt solar panel, a 12v 150Ah lithium (LiFePO4) battery or a 300Ah lead-acid battery would be the best suit.

To calculate the size of a battery bank I would suggest you consider the highest number of peak sun hours and multiply the number of peak sun hours by the rated wattage of your solar panel. 

For example

If I had a 300 watt solar panel. 6 peak sun hours (July, which is the highest number). 

6 * 300 = 1800Wh or 1.8kWh

For a 12v battery divide the calculated value by 12, and 24 for a 24v battery system. 

1800/12 = 150Ah 

A 300-watt solar panel will produce about 150 amp-hours of power output per day under ideal conditions. Considering 6 hours of peak sunlight. 

Lead-acid, AGM, and gel batteries have a depth of discharge limit (DoD) of 50%. Which means you can only draw them 50%. 

But the lithium-ion (LiFePO4) battery type is the only one that can be fully drained. 

What size inverter for a 300-watt solar panel

The size inverter will depend on your wattage consumption or how many watts of appliances you’d like to run. 

For Example

After calculating, your total energy consumption is 500 AC watts. 

500 * 1.2 = 600 watts 

You’d need a 600-watt inverter to run 500 AC watts. 

How Many 300-watt Solar Panels To Run a House

According to the U.S information administration (EIA), the average electricity consumption of US residential customers is about 893 kWh per month. So you’d need about 20x 300-watt solar panels to run an average house in the US fully on solar power.

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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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