Authors Note: This has been updated on Feb 23, 2022 with updated information, links, and resources.
From a small 50 watt portable solar panel to keep your devices charged to powerful 300 watt panels to mount on the roof of your tiny home or cabin, there’s a solar panel for everyone. How many panels do you need to keep things charged up in your home? Is it possible to run a refrigerator on a solar panel? With some simple calculations it’s easy to ensure your solar installation will meet your energy needs.
How do solar panels work
First let’s talk about the basics of how solar energy is generated. Photovoltaic solar panels are made up of many solar cells made of silicon. When sunlight hits the panels, they create an electric current. Panels have both a positive and a negative layer, which creates an electric field.
The current collected by solar panels then feeds into a charge controller, which controls how much current goes to a battery. Charge controllers prevent batteries from being overcharged. They also have the ability to shut down a system if the energy stored dips below 50%. Batteries store and produce DC power. In order to use AC appliances, such as microwaves, laptops, and phone chargers, an inverter is used to change the power from DC into AC power.
In a home, solar panels are connected to a grid inverter, which is then connected to the existing electrical network in your house. In an RV, van, or boat, you can choose from a range of different inverters based on your specific energy needs.
How many solar panels do I need to run a refrigerator?
The average refrigerator takes about three or four average solar panels to run. The average refrigerator found in the United States uses approximately 57 kWh per month while the average freezer uses 58 kWh. Adding those together brings a combined total of 115 kWh.
A 100 watt panel receiving at least 8 hours of sunlight per day will produce almost 1 kilowatt-hours per day or 30 kWh per month. Divide that usage of the refrigerator (115kWh) by 30 kWh per month and you get 3.8 solar panels. This means you’ll need four panels to keep this refrigerator running
What can you run with a 300w solar panel?
A 300 watt panel that receives 8 hours of sunlight per day will produce almost 2.5 kilowatt-hours per day. If we multiply this by 365 days per year, we get a solar output of about 900 kilowatt-hours annually. In short, each panel will provide 900 kilowatt-hours each year.
Considering all of the different scenarios, there is still a long list of appliances and devices that can run effectively with 300-watt solar panels, including laptops, LED lights, stereos, and TVs.
A 300-watt solar panel is at about the upper end of what you could reasonably be looking for in portable applications. They can provide significant power generation when taken on the road for RV vacations or other trips. These panels are available in compact enough sizes to take to remote sites where some power generation is required.
To get an accurate calculation of what you can and cannot power with a single 300w solar panel, you’ll need to compare the output per day or month (so 2.5 kWh/day for the solar panel) with the needs of an appliance (3.8kWh/day for a refrigerator). In this example, a 300 watt solar panel would not be enough to power that refrigerator.
Three hundred watts is a typical size for the solar panels that make up the solar array for powering a home or business. You'll require multiple panels to generate enough power, and the actual number you need can vary widely based on the size of your home and your individual energy consumption.
What can a 500 watt solar panel run?
Let’s assume that each panel gets around 8 hours of sunlight per day on your rooftop. A 500 watt panel receiving 8 hours of sunlight per day will produce about 4 kilowatt-hours per day. If we multiply this by 365 days per year, we get a solar output of about 1460 kilowatt-hours annually. In short, each panel will provide 1460 kilowatt-hours each year.
Buying a combination of these larger panels will help you meet the need of more energy-hungry appliances, such as refrigerators, stoves, hot water heaters, and dryers. However, they're the perfect size for certain applications all on their own.
They're particularly popular for RVs, delivering sufficient power to provide for most electrical needs and charge batteries for overnight use. At 500 watts, solar panels have reached a size that is getting less portable. However, there won't be any issue attaching such a panel to a recreational vehicle for portable power anywhere you go.
You'll have no trouble running laptops and other mobile devices for multiple people with a 500-watt solar panel. In fact, you'll have plenty of power left over for your RV’s lights and fans. You still aren't quite up to running the RV’s air conditioning off the solar panel, but the extra capacity will certainly help.
How many amps does a 300w 12v solar panel produce?
In order to effectively understand what your solar power system will be able to power, you'll have to understand amps in addition to watts. Amps are a measure of current, as opposed to power, and play a key role in determining battery bank sizes. To calculate amps, remember the equation amps x volts = watts. In this example, amps x 12 volts = 300 watts. Using this, we learn that this panel will produce 25 amps.
While 25 amps is the current you get based on the ideal match for your solar panels, there are more considerations to take into account in practice.
When charging a 12-volt battery bank, you'll actually be charging it up to 14.6 volts. Of course, this will also be different for different voltages, with some larger solar systems running on 24 or 48 volts to be more efficient at their scale.
There are also some points within the system where you can have energy losses.
The charge controller is one of the most important components when determining your actual electrical output. It regulates the flow of electricity from the solar panels to the batteries. There are two different types, pulse width modulation (PWM) and maximum power point tracking (MPPT). MPPT charge controllers are more efficient than PWM. Once you actually put your solar panels into action, you can expect about 16 amps at 12 volts from a 300-watt panel.
How many solar panels do I need to go off-grid?
For the cases of this example, let’s say we have some 300 watt solar panels, and you’re looking to provide power for your home. You don’t have access to the grid and installing off-grid solar on your home is your best option for meeting your energy needs.
Let’s assume that each panel gets around 8 hours of sunlight per day on your rooftop. A 300 watt panel receiving 8 hours of sunlight per day will produce almost 2.5 kilowatt-hours per day. If we multiply this by 365 days per year, we get a solar output of about 900 kilowatt-hours annually. In short, each panel will provide 900 kilowatt-hours each year.
However, you can't expect to get your solar panels' full output for every hour the sun shines during the day. In practice, the average output tends to be more in line with 4 hours of full production each day. This average means that your 300-watt solar panel is going to give you 1.2 kilowatt-hours of electricity per day.
Keep in mind that this is the total energy production over the course of the entire day. Power generation isn't consistent throughout the day. There will be a peak around noon with a noticeable drop-off as night approaches.
If your solar power system doesn't have sufficient battery storage, you'll be wasting any power you make at the peak. You need to make sure you have enough batteries to buffer this output.
How much energy does your home use? Most data suggests that a typical American home (2,000 square feet home) consumes approximately 11,000 kilowatt-hours annually. So, when we divide our total consumption by the expected output of one solar panel, we see that roughly thirteen solar panels of this size would be enough to power a home of that size. If you have a smaller home or are powering an RV, your energy needs will be much lower, and you’ll need fewer panels.
How many solar panels do I need to power my air conditioner?
Central air conditioners take up a lot of energy and use about 3,5000 watts, or 3.5 kWh, for every hour that they are in operation. That means each solar panel will be able to power your A/C for about 8.5 hours. However, if you run your A/C for 6 hours per day, that means you would need more than 21 100 watt solar panels to cover 180 hours per month of use. If you have a smaller solar installation, you’ll want to limit your AC use or forgo it altogether.
How many solar panels does it take to charge a 100ah battery?
Again, we use the same calculation dividing power in watts by the voltage in volts to find amps. Charging your battery at 12 volts and 20 amps will take five hours to charge a 100-amp hour battery. By multiplying 20 amps by 12 volts, 240 watts is how big of a panel you would need, so we'd recommend using a 300w solar panel or three 100-watt solar panels.
You'll still have your regular power demand when charging batteries for overnight. If your solar power system is only large enough to charge batteries for overnight, you won't have any power during the day.
One of the most important things that you should consider when determining the right number of 300-watt panels and 12-volt batteries for your solar system is that you'll have to run your system and charge batteries simultaneously.
When sizing a battery bank, it's also important to consider that the inverter could become a limiting factor in your solar power system.
This device takes DC power from your panels or battery and converts it to AC. Inverters have a maximum power throughput in watts, and you can't draw more electricity than the inverter allows, even if you have the battery capacity.
Do solar panels work in cloudy areas?
Even if you’re in a cloudy area, solar panels produce around 25 percent as much energy as they would on a sunny one. Also, despite popular belief, solar panels actually operate more efficiently in colder climates than in warmer ones. Your 300-watt solar panel has been designed to produce 300 watts of power when operating at 25°C. Its peak output can actually be higher at lower temperatures.
It's also important to consider the impact that solar panel positioning can have. Your solar panels need to be somewhere where the light hitting them isn't obstructed, which is why so many homeowners put them on their roofs.
More remote locations like cottages will often mount solar panels on poles. One key benefit here is that these systems can often be rotated to follow the sun for the most efficient power production possible. Getting the right angle is also important, but very fine adjustments have only minimal impact on energy production.
However, if you know you’re going to be mostly travelling or living in mostly cloudy areas, it’s important to take that into consideration when considering how much power your system will be able to generate and if that investment in the system is worth it. Refer to the Renogy Solar Calculator to get a more accurate estimate of what size system you need.
What do I do at night when my panels aren’t producing power?
If you are off-grid, your panels will have stored excess energy in your battery bank for you to tap into at night when your panels are not collecting power.
If you are on-grid, you can often take advantage of a utility billing mechanism called net metering. This is when excess electricity your panels are produced during the day are fed into the grid and credited to your account. Then, at night or when it’s cloudy, you can utilize those credits.
Net metering isn't necessarily offered by all power companies within the United States. You'll have to reach out to your utility company ahead of time to make sure.
When you do, you might also find out about certain tax incentives and other rebates available in your state. These incentives can make solar power an even better investment than it already is.
In theory, net metering could allow you to avoid the need for an extensive battery bank. The economics work out, with your solar power system producing excess energy and sending it to the grid throughout the day, then getting it back at night.
However, having a battery bank gives the added benefit of providing power storage when the grid goes out. You can still save money with net metering, but it can't keep your lights on during a power outage.
How do I know how many panels I need?
To determine what size system will best fit your needs, make a list of all the appliances and devices you plan on running. The main appliances to take into consideration when addressing energy needs may include a TV, lighting, water pump, laptop, fans, microwave, and refrigerator. We recommend using the solar panel calculator(refer to the video below) to help design your system and calculate your needs.
The solar sizing calculator allows you to input information about your lifestyle to help you decide on your solar panel requirements. You’ll just need to know what total watts your electronics will consume, how long you plan on running devices, your charge controller efficiency, and average sun hours per day. The solar panel calculator will then be able to tell you the minimum and recommended system size, as well as the recommended battery output.
One of the most important elements of correctly sizing a solar power system is understanding the difference between peak and average usage.
For example, your microwave might consume 1000 watts, but how often is it running? If you look at something like lightbulbs that have low wattages but are on for hours at a time, you have the opposite idea to consider.
Many appliances also have start-up loads higher than their listed wattage, which means they can draw much more power right as they're getting started. Taking a look at your energy use at this depth can be challenging but will help ensure that you get the capacity you need.
Renogy has a variety of different sized solar panels and solar kits available for purchase. Taking the time to do some math on the capacity of your solar panels and the needs of your household appliances and devices will ensure you have an effective solar installation that meets all your solar needs.
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