How To Determine What Can A 400 Watt Solar Panel Run?

I have seen that most of the online publishers are missing some key points when answering what you can power with a 400W solar panel

A 400 watts solar panel can run a fridge, ceiling fan, laptop, LED lights, Desktop computer, Domestic Water Pump, Electric Blanket, Projector, Sewing Machine, Water Dispenser, Humidifier, Curling iron, and other appliances which require under 300 watts of input power

I have two 200W Renogy solar panels which I use on my weekend RV trips, So in this guide, I'll share with you the realistic expectation of what will a 400W solar panel run

To determine what can a solar panel run or power will depend on these factors

  • Weather conditions & Power output
  • Battery bank size
  • Charge controller type
  • AC vs DC Watts
  • Inverter efficiency rate

400-watt solar panel power output

On average, A 400-watt solar panel will produce 1.6 kWh – 2.6 kWh per day or 250-340 watts of power per hour. Depending on the weather conditions, your solar panel tilt angle, and the number of sun hours your location receives per day.

Your 400W solar panel is designed to produce 400 watts of power per hour but in standard test conditions STC (radiation of 1 kW/m2, a cell temperature of 25°C, and no wind).

But in real life it will rarely happen when you'll receive the 100% output from your solar panels, So from my personal experience, I live in Florida city and here I receive about an average maximum of 80% power output

400*0.8 = 320 watts 

So on average, I receive 320 watts of power output per hour from my 400W solar panels during peak sun hours.

That is because you'll never receive the ideal conditions so your solar panels can perform at their maximum capacity

Sun-hours - Are not the number of sunlight hours but the number of hours when the radiation of the sun is 1 kW/m2

Every location receives different hours of peak sunlight in which your solar panel can produce the maximum power. Here you can check the peak sun hours by entering your location

Like here in Florida city on average we receive 4.9 hours of peak sunlight

320*5 =  1600 or 1.6kWh

This is what I receive from my solar panels on average during the peak sun hours (this number goes high in summer but decreases in winter)

You can make it up to 2000 watts or 2kWh if you place your solar panels under the sun from the morning till night. In summer it can go up to 2.6kWh

Also with the help of a right tilt angle, you can maximize the power output

I have covered this topic in very depth which you can read after this post to get the maximum output from your solar panels

Must Read: How much power can a 400W solar panel produce?

Choose the Right Size Battery

The solar panel is a device that will convert the sunlight into DC (direct current). So you have two choices

1- you can use that power instantly with the help of a charge controller and inverter
2- you can store that power for later use

Running your devices directly from the solar panel can be risky and can create damage to the system, but there is a way that you can use and I have discussed it in this blog post

batteries are one of the most important but costly components when it comes to living off-grid

So choosing the right size battery will allow you to store the maximum power produced by the solar panels

We already know about the power output of our 400W solar panel but we'll go with the 3000 watt-hours of power (Which will give you some room to store some extra power in case if you haven't used all the power produced by solar panels previous day)

Now calculate the Wh in Ah (because the battery capacity is measured in amp-hours)

3000Wh / 12V system = 250Ah 
3000Wh / 24V system = 125Ah 

If you choose to go with a 12v 400W solar system you'll need a 5 100Ah lead-acid, AGM or Gel batteries, or 3 100Ah lithium batteries and for a 24v 400W solar system you'll need 150Ah lithium or 250Ah of lead-acid batteries

With this size battery bank with your 400W solar panels, you'll be able to store the 100% of the power produced by your solar panel which you can use later on to run your appliances (like fridge, microwave, lights, TV, and other heavy appliances)

Also, one more thing that you need to keep in mind is the C-ratings of the battery which in simple words is the recommended charge and discharge rate, and every battery type has its different C-ratings, Which I have discussed in detail in the mentioned article

Related Post: 400-watt solar panel how many batteries?

Choose the right size and type of charge controller

The charge controller or regulator is the device that regulates the current and voltage coming from the solar panel to charge the battery bank.

For example: a 12v solar panel will produce 18-20 volts under direct sunlight but you're using a 12v battery so here the controller will lower the voltage to 12v

Here's an interesting part, if you're using a PWM charge controller it will reduce the voltage but will not increase the amps which in result will cause a huge power loss (watts = amp*volts)

But on the other hand, the MPPT charge controller will reduce the voltage but will increase the amps which makes them 30% more efficient than the PWM charge controller

40A MPPT charge controller is recommended with a 400W solar panel

AC vs DC Watts & inverter efficiency rate

Solar panels convert the sunlight into DC (direct current) and our batteries store power in DC but most of our household appliances required the AC (alternating current)

So for this, we use an inverter that converts the DC into AC but there will be a power loss due to their efficiency rate. Most of the inverters are 85% efficient which means there will be a power loss of 15% when using an inverter

So to get the number of AC output from your 400W solar panel multiply the total watt-hours by 0.85 (for an 85% efficient inverter)

2000Wh*0.85 = 1700 AC watt-hours

Laptop chargers, portable Fan, DC ceiling fans, mobile chargers, and other small appliances use DC power but most the large or heavy appliances like fridge, microwave, TV, computer, etc use AC current

Why does this matter? Let's assume, that your solar panels are producing 350 watts of power under ideal sunlight conditions and your batteries have reached their DOD (depth of discharge limit) so in this scenario, you shouldn't connect a load that is higher than 350 DC watts or 297 AC watts (inverter efficiency loss)

Video - Running tools on 400W solar panel without inverter

What Can A 400 Watt Solar Panel Run?

A 400W solar panel can run many appliances including, a TV, Fridge, Fan, and other appliances which require under 300W input power.

this is just an example of what you can run on your 400w solar panel, but A rule of thumb is that the output from the inverter should not exceed the output of your solar panels if the battery is fully discharged or close to its discharge limit.

What you can run from your solar panel will highly depend on the size of your battery bank which I have discussed with you in the above session.

Can a 400-watt solar panel run a refrigerator?

A refrigerator consumes between 100-200 watts per hour depending on the size, so a 400-watt solar panel can run a refrigerator for a minimum of 16 hours

A small refrigerator like a 12v RV inverter consumes a small amount of power but on the other hand, a large-sized old technology fridge will consume up to 200 watts of power per hour.

Check the description of your fridge and there will be an input watt number. Divide that number by 3 and then multiply it by 2 (because normally a fridge will be consuming power for only 40 minutes in an hour) this will be the amount of power your fridge will consume per hour

To run a fridge you'll need a minimum 500W pure sine wave inverter connected with the battery

Still have any queries? 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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