The early spring of 2022 has brought record-breaking prices of energy. In some countries like the United Kingdom, we could experience an increase in energy price up to 50 percent. It is one of the highest price rises for customers that the conventional energy sector has seen so far.
The current energy situation is rather unstable and could make some of us worried. Luckily, there are alternatives how to power your home, and their performance is not only promising for your energy demand but also for the long-lasting and sustainable future development. We talk about solar energy, the renewable form of energy production with smaller environmental footprint.
Solar panels for homes are becoming more affordable and accessible than ever before. It took 40 years for the number of solar panel installations in the United States to surpass the one million mark, which it did in 2016. But just three years later that solar installation total had doubled, and by the end of 2021 the number of American homes and businesses using solar energy should have exceeded three million according to projections.
If your community is like many others today, you’re seeing more and more solar panels installed on your neighbors’ rooftops. Solar photovoltaic system installations are booming. If you’re starting to think about saving money on your electricity bill with clean solar energy, you’re probably questioning, “How many solar panels do I actually need for my house?”.
How many solar panels to power an average home in 2023?
The average American home will require somewhere between 21 and 34 solar panels to meet 100 percent of their energy needs. How many solar panels your home needs depends on a few key factors that are linked to your personal energy usage habits, geographic location of your house with the number of peak sun hours throughout a year, and specifics of solar panels you are considering to buy (power rating and energy production ratio).
The number of solar panels needed varies from house to house and is crucial in determining what set up would work the best for you. But don’t worry, you won’t have to guess how many solar panels your home requires. It is not difficult to make a simple calculation to give you the information you are looking for on your own.
The equation you need to use to get started and determine how many watts your solar panels need to produce is following:
Based on this information you will be able to proceed with making the decision about what type of solar panels you will select.
Let’s break down each piece of the equation to get started.
I. Your monthly energy consumption
The first step in finding out the size of a solar system that will generate enough power to meet your energy consumption is to calculate the amount of electricity you use, as this can vary a lot from household to household.
As an example, let’s assume two families live next door to each other in 1,000 square feet homes (around 93 square meters). A single guy lives in Home A and he often spends evenings out in the city with friends or looking for his soul mate. Being alone, and most of the day out, he doesn’t use much electricity and pays about $50 a month.
In Home B, two parents live with a teenage kid. They are using the heater or air conditioner often during the day and use electricity to filter their swimming pool, meanwhile the teenager is always on his iPad or watching TV. Since more people are living in the house and their way of life requires more energy, they pay $200 a month on electricity.
So even though the houses have the same size, the family in Home B would need to consider installing more solar panels to make up for their electricity usage than the single guy in Home A.
In your case you can think of it like this: The more energy your home uses, the more energy has to be produced by your solar PV system. Therefore, the more solar panels you are going to need.
How much solar power will your house need?
To find out your average energy usage, check your past utility bills. More precisely the last 12 months of your bills (so you include summer and winter months as energy consumption varies throughout the year). Look for the total number of killowatt-hours (kWh) you consumed every month.
Sum the numbers up and divide them by 12 to get the average. An easier way to determine your total energy consumption for the past year is to simply call your utility company and ask them to provide you the details.
To get even more reliable information, do the calculation for the past two or even more years. This will allow you to get the most accurate overview of your long-term energy consumption.
Based on the data available from the U.S Energy Information Administration, in 2019 the average family home in the United States consumed 10,649 kilowatt-hours (kWh) of electricity, or about 900 kWh of electricity per month. That’s 30kWh per day.
Obviously, your household can consume more or less electricity depending on how big your house is, how many family members live in it, the appliances you have and how energy efficient you are.
II. Monthly peak sun hours at your location
Peak sun hours (or average solar radiation) express the number of hours per day when the sun is more or less directly above the solar panels. This number interests us because it is during these hours (usually in the middle of the day) when your solar panels will be producing the vast majority of their daily energy.
Peak sun hours vary based on season and your geographical location – apparently, the closer you are to equator, the more peak sun hours your solar system would get each day and more energy your solar panels produce.
For example, California has more sunny days annually than Washington. In this case if you live in Washington, you would need a bigger solar system to get the same power as you would get with a smaller system in California.
Luckily, there are reliable resources with this information freely available for anyone. You can visit the National Renewable Energy Laboratory (NREL) and get detailed maps for each month of the year.
Even more detailed maps about available solar radiation at different global locations is from The Global Solar Atlas. The tool even provides a rough estimate of how much residential photovoltaic panels would produce based on your location and some additional information.
Just be careful. The number of peak sun hours you get from these maps is per day. You need to multiply it by 30 to get the monthly average. For example, your area gets 5 hours of peak sun a day throughout the month of June, you need to multiply 5×30 to get a number for a whole month of June.
To get an average monthly number of peak sun hours for your equation, you need to make monthly averages of each month of a year and then calculate their average. This number is what you need for the equation.
III. Getting the number of watts solar system needs to produce
When you divide your monthly energy consumption by average peak sun hours, the resulting number you get will tell you how big your solar panel array will need to be to meet 100 percent of your electricity needs. The result will be expressed in kWh.
For example, if you consume 1,000 kWh of power each month, and live in an area with an average daily peak sun hours total of five, the calculation goes like this:1,000 divided by (5×30) 150. The result is 6.67 kWh—which is the size of the solar energy system you need to purchase to meet all of your energy needs.
To convert this into actual solar panels, you’ll need to multiply the result by 1,000. This converts kilowatt-hours (kWh) into watts. In our example, 6.67 would become 6,670. You need this information because solar panels are rated by the number of watts they are capable of producing. Solar panel wattage expresses power production of a panel under standard test conditions when the amount of sunlight and temperature allows for the highest efficiency.
An average photovoltaic solar panel will likely be rated somewhere around 250 watts, which is an expression of its power-producing potential. Supremely high-efficiency panels could reach to 400 watts, and there are many solar panels that fall somewhere in between the lower and upper limits.
If you decided to install standard-size panels in our hypothetical example, you would divide 6,670 watts you need in total by 250 watts. Your final answer would be 26.7 solar panels rated at 250 watts. This would mean you need to purchase 27 standard-sized 250-watt solar panels to meet 100 percent of your home energy needs.
Few things about solar panel output efficiency
Solar panel type and quality make a significant difference in terms of solar output and efficiency. Not all solar panels are the same.
The amount of power (kWh) your solar energy system can produce depends on the number of solar panels and efficiency with which they convert solar energy into electricity.
Why does efficiency matter? This number informs you about the ability of a solar panel to convert sunlight into energy. Standard solar panels have efficiency around 18 percent, but the span of most marketed products lies between 15 to 22 percent.
If you have a solar panel with 20 percent efficiency and one with 15 percent right next to each other under the same conditions, the more efficient one will produce more energy over the same period of time.
When determining how many solar panels you need, you have an option to reduce the number of panels by simply purchasing higher efficiency panels. This option may be a good option if you have limited roof space.
For instance, monocrystalline photovoltaic (PV) solar panels are known to be the most efficient solar panels on the market, but also the most expensive.
Their two main advantages over the less efficient types of solar panels (such as polycrystalline or thin film panels) is that 1) they absorb more sunlight and their output efficiency is not affected that much by temperature and 2) they occupy less space. These are an ideal option if you do not have enough roof space for more panels.
On the other hand, less efficient polycrystalline or thin film panels are cheaper, but you need to count with having more panels to provide the amount of power you need.
Because of these wide differences in quality and efficiency, it’s up to you to decide which solar panels are right for your home.
The main takeaway is that the more efficient the panels are, the more power they can produce, and the fewer photovoltaic panels you will need on your roof to get the same energy output as you would get with less efficient solar panels.
How many kWh can solar panels produce and how many panels you need on your roof?
Assuming you are going to choose standard-efficiency solar panels rated at 250 watts, here are the most common sizes for residential solar systems and their kWh production potential to give you an idea of how many solar panels you would need to run a house.
- A 3kW solar system which consists of 12 panels can produce an average of 4,200 kWh per year. You will need a roof space of about 211 square feet (19.6 square meters) for this system.
- A 5kW solar system which consists of 20 panels can produce an average of 7,000 kWh per year. You will need a roof space of about 352 square feet (33 square meters) for a 5kW system.
- A 10kW solar system which consists of 40 panels can produce an average of 14,000 kWh per year. You will need a roof space of about 704 square feet (65.4 square meters) for a 10kW system.
The average size of a photovoltaic solar panel is 65 inches long and 39 inches wide (165 centimeters to 100 centimeters). If you would like to calculate how much roof space you approximately need for the number of panels you are planning to get, multiply the number of panels by the area of a standard solar panel – 17.6 square feet. From the example above: 12 panels times 17.6 equals 211 square feet.
Some panels could be slightly bigger in size, depending on the wattage as well as the specifics of a manufacturer. You need to check with your provider for exact data.
How much energy do you want to offset with solar power? What are the alternative options?
Typically, most people want to offset as close as possible to 100 percent of their power consumption. However, not everyone can afford to offset all energy consumption with a stand-alone solar system as the overall cost of the full home solar power system and its installation can get quite expensive.
Installing a smaller system and participating in the net metering program is still a great way to reduce your electricity bill up to 50 percent or more. Net metering is one of the best solar incentives widely available in many countries. Some states have even passed net metering laws, in other the participation is voluntary.
How net metering works?
Let us assume that you are gone in a vacation with your family. The solar system still generates energy when you’re gone but since you are not using it, it’s being automatically sent back to the grid.
When sending energy to the grid, the electricity meter runs backwards, giving you credits for extra unused power your panels produce. As a result, your annual electricity bill will decrease according to how many credits you have.
The solar energy your system has supplied to the grid is typically distributed to nearby customers. There is no denying that this way of energy generation is beneficial for your household but also climate-friendly.
However, you should be aware that the utility company will not pay you for the energy produced by your system. You only receive a “credit to spend” on using electricity from the grid in times your system doesn’t produce enough. Keep that in mind when deciding on getting solar panels and determining how much of your energy consumption they should offset.
Knowing the answers to the above questions will give you a good understanding of the number of panels needed to achieve your daily energy production goals and will allow to calculate in a realistic range solar panels needed for your home.