What Can A 400W Solar Panel Run?

Have you got a 400W solar panel and want to know what it can run? Perhaps you have been considering purchasing solar panels and want to know what they could do?

What Can A 400W Solar Panel Run

Or are you curious and want to know more? Whatever brought you here today, we have the answers for you! 

Solar panels are an excellent addition to homes, allowing you to save some money on your energy bills and power your home more sustainably.

But what can they run? The last thing you want to do is purchase a solar panel and then find out it can barely turn a light on or boil a kettle. 

So you head online and start searching. But no matter what you do, you can’t find the answers that you need. You find yourself stressed, frustrated, and unsure where to turn.

Maybe you will never know what a 400W solar panel can run. 

Well, no more! Today we have the answers for you! Keep reading to find out what a 400W solar panel can run and have all your other solar panel-related questions answered! 

How Much Electricity Does A 400W Solar Panel Produce?

Before we dive in and find out what a 400W solar panel can run, we first need to see how much electricity it produces.

To do this, we need to look at how much energy in watt-hours your solar panel generates, and the best conditions for this. 

It’s more useful to measure energy output in watts-hours with solar panels than power in watts, as it helps you to compare solar panels and their performance more accurately.

Let’s start by taking a look at the specifications of a 400W solar panel to learn more about them and help to determine the amount of electricity they can produce. 

400W Solar Panel Specifications 

When looking at solar panels, there are a few main specifications we need to look at. These are listed below for you: 

  • Voc (open circuit voltage) – this voltage is measured by a multimeter when connected to positive and negative leads 
  • Isc (short circuit current) – is the amps that flow when leads are shorted together 
  • Vmp (maximum power voltage) –  is the maximum power you get at this voltage 
  • Imp (maximum power current) – is the maximum power achieved when the current flows 
  • MPP (maximum power point) – is when the voltage and current combine to generate the panels most power and is recorded in watts. 

You must keep these features in mind when looking at solar panels. They will tell you what you can expect from your 400W solar panel. Now, let’s take a quick look at a 400W solar panel that could be the best choice for you! 

Renogy 400W Solar Panel Kit And Controller 

Renogy’s 400W Monocrystalline Starter Kit is the ideal choice for those new to the world of solar panels.

The kit is super diverse and can be used as emergency power, to charge your batteries or everything in between!

The kit is a fine choice and made with the highest quality, so you don’t need to worry about it breaking any time soon.

The kit also comes with a twenty-five-year performance warranty and a ten-year materials warranty.

You don’t need to worry about anything going wrong, as you are likely to be covered for any repairs or replacements. 

Whether you are new to solar panels or looking to expand your power system, the Renogy kit is sure to fit right in.

It’s also ideal for off-grid applications like cabins, boats, sheds, trailers, and RVs. Whatever your need might be, the Renogy kit is a fine choice! 

How Much Electricity Does A 400W Solar Panel Produce? 

Let’s revisit our earlier question and see how much electricity a 400W solar panel can produce!

Now, the amount it produces will vary depending on a few different factors, so there will be assumptions made here. 

If we assume that you have an average irradiance of 4 peak sun hours, then a 400W solar panel will generate 1600 Watt-hours (Wh) of energy a day, translating to 584kWh per annum.

Now, the exact value does change depending on your location and its peak sun hours. 

You should also subtract 10% to take into account inverter losses. Again, these losses will vary from panel to panel, depending on the inverter size and load. 

Another thing we need to be aware of when calculating how much electricity your solar panel produces is the maximum power point.

This is the point where the amps and volts in the panel are at the right value to generate the maximum power of the panel. To work without we need the following calculation: 

Power (in watts) = current x voltage 

For the maximum power to be generated we need the characteristics of the load resistance to match the panel’s internal resistance and for the sun’s energy, known as irradiance, to be strong enough. 

The Relationship Between Solar Irradiance And Power Output 

Let’s take a closer look at solar irradiance now and what this means for the power your solar panel can produce.

The output of your solar panel will vary depending on the strength of the sun, which changes throughout the day.

You will have a higher output during its strongest hours, either side of midday, and then a lower output in the early morning and evening when the sun is not as bright. 

When it comes to solar panels, we talk about average hours of sunshine per day and use this to estimate the watt-hours a panel can generate over time.

The peak hours of sunshine will vary depending on your location, but you can check this by searching for historical solar data online. 

Solar Panel Characteristic Resistance 

Every electrical device comes with internal resistance. For solar panels, we call this the characteristic resistance. Most panels will have an internal resistance of roughly 3 ohms.

When the characteristic resistance reaches the same value as the load resistance, the panel will achieve and generate its maximum power. 

Inverters and solar chargers will adjust their internal resistance automatically to create this maximum power output.

These are known as MPPT, or Maximum Power Point Tracking, devices. 

How Much Energy Will A 400W Solar Panel Produce?

Now that we have all this new information rattling around in our brains, let’s take a look at how much energy a 400W solar panel can produce.

What Can A 400W Solar Panel Run (1)

To calculate the amount of energy you can expect your solar panel to produce, you can use the following formula: 

Solar panel rating x peak sun hours per day (irradiance) = energy in watt-hours a day. 

Let’s give you an example for you to see! We will use Las Vegas and their peak sun hours to show you the energy a 400W solar panel can produce. 

400W x 5.701 = 2.28kWh/day 

We can then take the 2.28kWh/day and multiply it to get an annual energy production of 832kWh/year. 

What Can A 400W Solar Panel Power?

Let’s get into what brought you here today and take a look at what a 400W solar panel can power!

A 400W solar panel with full irradiance can run a constant load of 360W when taking into account the 10% inverter loss. 

Considering the load of 360W, let’s see the watt rating of some common household appliances that your solar panel could run in perfect and sunny conditions! 

ApplianceRating (watts)
Ceiling Fan60
Corn Popper275
Dehumidifier 240
Desktop Computer100
Electric Can Opener170
Electric Blanket200
25 miles of Electric Fence250
Electric Hedge Trimmer300
Food Processor360
Home Sound System95
Laptop Charger125
Paper Shredder220
Projector 270
Rice Cooker200
Slow Cooker160
Vacuum Cleaner200

As you can see, there are lots of appliances that based on the wattage, your solar panels could produce more than enough power for! 

How Many Amps Does A 400W Solar Panel Produce? 

Now, the maximum current a 400W solar panel has is known as an Imp or maximum power current.

You can find this information by checking the specification sheet or user manual provided by the manufacturer.

You can also check online by reading product descriptions or downloading a PDF copy of your user manual. 

On average, a 400W solar panel will have an average current of 9.5 amps and a voc of 49 volts. So, when it comes to running AC appliances, your solar panel can run those with 3.3 amps.

Remember, this is just an average and you should check your user manual to find out how many amps your solar panel has. 

You will also want to deduct 10% when converting your AC to current to allow for inverter losses. 

Let’s take a look at how you can do these conversions and get the answers that you need! If we take a Vmp of 42 volts, then you will want to reduce the DC valuer by the ratio of DC to AC voltage. Y

ou can use the formula below to see what that will look like: 

AC = DC x 42/120 = 9.5 x 0.35 = 3.325 amps AC

As we said earlier, inverters aren’t the most efficient device. If they are not loaded to 100%, you can expect them to drop sharply when the load decreases.

How much the inverter decreases will depend on the size of the inverter and as the load does not remain constant, you can expect the efficiency to change while the solar panel and inverter are working. 

Again, you can use the formula below to make your deduction based on inverter losses and see a realistic amps rating. 

Final AC load current = 3.325 – (3.325*5/100) = 3.16 amps AC 

Dimensions Of A 400W Solar Panel – How Big Is It?

The size and dimensions of your solar panel will depend on how many solar cells are used during production. Generally speaking, most panels will be between 40 mm and 55 mm thick and weigh between 20kg to 25kg. 

We tend to see a surface area of 2050mm x 1050mm, with the thickness varying depending on the manufacturer.

The solar cells tend to have the same thickness across the board, but extra layers of solar backing, glass covers, and EVA plastic can impact the thickness.

Generally speaking, they don’t tend to impact the thickness by too much. 

Before purchasing a solar panel, we recommend that you check its dimensions to ensure that it is the right size for you and your space.

The dimensions should be listed in the product description for you to see easily. 

Can A 400W Solar Panel Run A Refrigerator?

Yes, a 400W-rated solar panel can run a medium-sized refrigerator. This will be in combination with a 120Ah lithium iron phosphate battery and a 500 or 600-watt inverter.

If your 400W solar panel can generate 584kWh/year and your refrigerator needs 200kWh to 400kWh/year then it seems like they are a good match!

But as always, we need to take a look at this in closer detail. Let’s assume the refrigerator needs 400kWh a year to run.

Your refrigerator runs continuously day and night, but your solar panels will only produce power during the day when the sun is out. 

So you will need a battery to power the refrigerator through the night. You would need this battery to power 50% of the energy needed, or 200kWh a year.

This is why we recommended earlier that you pair your solar panel with a lithium-ion battery. 

Providing that your solar panel can generate 200kWh a year to power the refrigerator during the day and that your battery is capable of generating the remaining 200kWh for the evening and night, then you can run a refrigerator with a 400W solar panel. 

Of course, you will need to take into account the weather, but providing there aren’t too many cloudy days, your solar panel should be able to power a medium-sized refrigerator! 

Will A Solar Panel Work Without A Battery?

Yes, a solar panel will work without a battery! Grid-tied solar systems work this way without a battery.

In the event there is an overproduction of energy, your solar panels will supply the excess to the grid!

While your solar panels will work without a battery, we recommend that you use a battery when using your solar panels to power any appliances. 

This ensures that if any clouds pass over or the weather changes that your appliances will continue to function as normal.

The last thing you want is the output to reduce and your appliances to turn off! 

Not all appliances require the same amount of power the whole time they are running either. AC units, freezers, and refrigerators don’t pull the same current all the time. Instead, they turn on and off when needed.

But when the motor starts, a refrigerator can pull up to three times more current than it needs when it runs constantly. 

This additional power is usually more than your solar panel can generate and is unlikely to have any reserves.

This is where your battery would come in handy and help to generate the added power needed to start the motor of your refrigerator. 

When deciding whether to power your appliances with a solar panel, be sure to check for any starting watt rating along with the running watts, so you can decide if your panel and battery can support the increased wattage or not. 

How Many 400 Watt Solar Panels Are Needed To Power My House? 

For the average house, you would need nineteen 400W solar panels to provide enough power. The average household in America uses 11,000kWh of energy every year.

What Can A 400W Solar Panel Run (2)

Now if we use our earlier calculation that a 400W solar panel can generate 584kWh per year with 4 hours of peak sun a day, we can work out how many solar panels are needed.

We did this using the following formula: 

Home energy needs/solar panel production = number of 400W solar panels needed. 

While that gives us the number of solar panels needed to generate the power for our home, it does not take into account any inverter losses.

So you would need to follow this with another formula. Let’s assume that you have a loss of 10% and do the following calculations: 

If each solar panel can generate 583kWh, we need to deduct 10% from this, giving us 525.kkWh (584kWh – (584kWh*10%) = 465 = 525.6kWh). 

Next, you will want to take the 11,000kWh needed to power your home and divide it by our new number, taking into account the inverter losses: 

11000kWh/525.6kWh = 21 panels. 

As you can see, you would now need an extra 2 panels to make up for the inverter losses over the year. 

Of course, this is just a rough guide. The amount of solar panels you will need depends not only on the amount of energy you use but where you live too.

After all, if you live surrounded by trees or in a colder climate then you might not get enough power from your solar panels! 

How Many Batteries Do I Need For A 400W Solar Panel?

A 400W solar panel needs a 166Ah lithium iron phosphate battery that has a DoD (Depth of Discharge) of 80%.

You could also use a lead-acid deep cycle battery if it had a capacity of 266Ah and a DoD of 50%. Your solar panel can then charge 133Ah at 12V. 

When it comes to storing energy for your solar panels, lithium-ion or lead-acid deep cycle, known as leisure batteries can be used.

You will need to ensure that it is discharged to the correct DoD though to prevent any damage to the battery. 

When it comes to recharging these batteries, you need to calculate what the average Wh of your 400W solar panel is. You can use the calculation below as a rough guide: 

400W x 4 hours of peak sun = 1600 watt-hours

This calculation tells you how much charging energy you have every day. So if you are recharging a 12V battery, then you can calculate the charging amp-hour capacity by dividing 1600Whs by 12V to give you 133Ah. 

You can use this to calculate how long your battery needs to be recharged to reach its correct charge.

Don’t worry, if you find yourself struggling with this you can always contact the manufacturer of your battery for more help! 

Final Thoughts 

And there you have it, your 400W solar panel is capable of powering a range of small appliances in your home, or a medium-sized refrigerator!

Just be sure you have a battery on hand to help with the extra power required and to power your appliances through the night.

Joe Danner