It's no use installing just one solar panel–you'll need more than that to reap the financial benefits of a solar panel system. While the answer isn't always so simple, we've put together some example cases to help you understand, at a high level, how many solar panels you need to install an effective solar array.
Making the switch to solar energy can help you lower or even eliminate your monthly electric bills while reducing your carbon footprint. However, before installing a clean energy system in your home, you must first answer an important question: "how much solar power do i need for my house? "
To accurately calculate the ideal number of solar panels for your home, you'll need a professional assessment. However, you can estimate the size and cost of the system based on your electricity bills, energy needs and available roof space. This article will tell you how.
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How many solar panels does the average house need? How many solar panels do I need for a 3-bedroom house? How many solar panels do I need for a 2000 sq. ft. home? These are all common questions for an aspiring solar homeowner. However, determining how many solar panels you'll need for your home requires first knowing your goals.
Do you want to minimize your carbon footprint? Maximize the return on your investment? Save as much money as possible?
How To Calculate How Many Solar Panels You Need?
The formula we used to estimate the number of solar panels you need to power your home depends on three key factors: annual energy usage, panel wattage, and production ratios. So what does that mean exactly? Here are the assumptions we made and how we did our math:
Annual electricity usage: Your annual electricity usage is the amount of energy and electricity you use in your home over a full year. Measured in kilowatt-hours (kWh), this number is influenced by the appliances in your home that use electricity and how often you use them. Refrigerators, air conditioning units, small kitchen appliances, lights, chargers, and more all use electricity. According to the U.S. Energy Information Administration (EIA), the average American household uses 10,649 kWh of electricity per year, so we'll use that number as the ideal solar panel system or solar array size, which would mean you could offset 100 per cent of your electricity usage and utility bill with solar panels (in practice, it's not this neat, but bear with us here). If you're interested in getting a more exact number based on your personal energy usage, check last year's utility bills to determine how much electricity you used. Once you have that number, feel free to plug it into the equations below.
Solar panel wattage: Also known as a solar panel's power rating, panel wattage is the electricity output of a specific solar panel under ideal conditions. Wattage is measured in watts (W), and most solar panels fall in the range of 250 – 400 watts of power. Therefore, we'll use 320 watts as a middle panel in these calculations.
Production ratios: A solar panel system's production ratio is the ratio of the estimated energy output of a system over time (in kWh) to the actual system size (in W). These numbers are rarely 1:1 – depending on how much sunlight your system will get (which is primarily based on your geographic location), your production ratio will change accordingly. For example, a 10 kW system that produces 14 kWh of electricity in a year has a production ratio of 1.4 (14/10 = 1.4) – this is an entirely realistic production ratio to see out in the real world. In the U.S., production ratios are usually between 1.3 and 1.6, so we'll use those two numbers as the high and low estimates for our calculation.
Factors That Determine How Many Solar Panels You Need
You may think that the size of your house determines how many solar panels you need, but it doesn't! To really understand how many solar panels your solar energy system needs, you need to determine the following:
- Your energy usage: The more electricity you use, the more solar panels you need to cover your electricity costs. Larger homes tend to consume more electricity, and they generally need more solar panels. However, they also have the extra roof space necessary for larger solar panel installations. There may be exceptions to this rule — for example, a 2,000-square-foot home with new Energy Star appliances may consume less power than a 1,200-square-foot home with older, less-efficient devices.
When it comes to installation, solar panels can be placed on many types of surfaces. However, your roof conditions may limit the number of solar panels your home can handle.
For example, if you have a chimney, rooftop air conditioning unit or skylight, you'll have to place panels around these fixtures. Similarly, roof areas that are covered by shadows are not suitable for panels. Also, most top solar companies will not work on asbestos roofs due to the potential health risks for installers.
- Sunlight in your area: Homes in areas that receive less sunlight will need more solar panels to eliminate their electricity bills than those in sunnier states. As a rule of thumb, the southwestern United States gets the most sun, while the northeast gets the least. Where there is more sunlight available, there is more energy that can be converted into electricity. The yearly output of each solar panel is higher in states like Arizona or New Mexico, which get a larger amount of sunlight than less sunny regions like New England.
- Panel Wattage: The wattage of the solar panels you choose, also called the power rating, determines how much energy the panels will produce and most solar panels installed today have a power rating of about 320 watts per panel; fewer panels are needed when you install panels with high wattage ratings.
How Many Watts Do You Currently Use?
Look at your electricity bill for average usage. Look for "Kilowatt Hours (or kWh) Used" or something similar, and then note the length of time represented (usually 30 days). If your bill doesn't show kilowatt-hours used, look for beginning and ending meter readings and subtract the previous reading from the most recent one.
You want daily and hourly usage for our calculations, so if your bill doesn't show a daily average, just divide the monthly or annual average by 30 or 365 days, respectively, and then divide again by 24 to determine your hourly average electricity usage. Your answer will be in kW. (And just in case you're wondering, a kilowatt-hour is how much power you are using at any given time multiplied by the total time the power is being used.)
A small home in a temperate climate might use something like 200 kWh per month, and a larger home in the south where air conditioners account for the largest portion of home energy usage might use 2,000 kWh or more.
How Many Solar Panels Do I Need To Power My House?
We estimate that a typical home needs between 20 and 25 solar panels to cover 100 per cent of its electricity usage. The actual number you'll need to install depends on factors including geographic location, panel efficiency, panel rated power, and your personal energy consumption habits. Importantly, the number of solar panels you need for your home directly impacts the price you pay for solar.
To more closely estimate how much energy you use annually, add up the kWh reported on your last 12 power bills. These numbers will fluctuate based on factors like the size of your home, the number of residents, your electricity consumption habits and the energy efficiency rating of your home devices.
To determine your home's average energy requirements:
- Look at past utility bills. You can calculate how many solar panels you need by multiplying your household's hourly energy requirement by the peak sunlight hours for your area and dividing that by a panel's wattage.
- Use a low-wattage (150 W) and high-wattage (370 W) example to establish a range (ex: 17-42 panels to generate 11,000 kWh/year).
- Note that the size of your roof and how much sunlight your roof gets are factors as well.
What Affects Solar Panel Output Efficiency?
Here's where solar panel quality makes a difference. Not all solar panels are alike. Photovoltaic (PV) solar panels (most commonly used in residential installations) come in wattages ranging from about 150 watts to 370 watts per panel, depending on the panel size and efficiency (how well a panel is able to convert sunlight into energy), and on the cell technology.
For example, solar cells with no grid lines on the front (like SunPower® Maxeon® cells) absorb more sunlight than conventional cells and do not suffer from delamination (peeling) issues. In addition, the construction of our cells makes them stronger and more resistant to cracking or corrosion. And a microinverter on each panel can optimize power conversion at the source, in contrast to one large inverter mounted on the side of the house.
Because of these wide variations in quality and efficiency, it isn't easy to generalize about which solar panels are right for you or how many you'll need for your home. The main takeaway is that the more efficient the panels are, the more wattage they can produce, and the fewer you will need on your roof to get the same energy output. Conventional solar panels usually produce about 250 watts per panel, with varying levels of efficiency. In contrast, SunPower panels are known to be the most efficient solar panels on the market.
Frequently Asked Questions About Solar Panels
One of homeowners' most frequently asked questions concerning solar power is, "can it really power my entire house?" The answer to that is actually quite simple – yes, solar can indeed power your entire home.
Solar power systems are finite resources—they can only produce so much energy consistent with the size of the system, and most utilities limit system size to the historical energy usage average at the site.
Do solar panels work at night/in the dark? Strictly no—solar panels are not too effective at night. But it's now easier than ever to store energy your panels produce during the day.
So, a 2,000 square foot home would be allowed a solar array of 4,000 watts. Depending on the type of panel that you choose, a system of this size would be anywhere from 12-18 solar panels.
Are Solar Panels Worth it for Your Home?
Solar panels produce no carbon emissions while operating. Although the initial investment in solar panels is steep, renewable energy systems make sense financially for many homeowners. According to the Department of Energy, they have a typical payback period of about 10 years, while their rated service life is up to 30 years. So after recovering your initial investment, you will have a source of clean and free electricity for about two decades.
Plus, even if you have a large home or find you need more solar panels than you initially thought you would, keep in mind that there are both federal and local tax credits, rebates and other incentives to help you save on your solar power system.
Individual solar panels can produce a certain amount of energy, depending on the conditions at your home (including how much sunlight you receive and how much shade covers your roof). This number is called a power rating and is measured in watts, with a typical panel generating between 250 and 400 watts of power. For example, you might buy a solar panel with a listed output of 325 watts. You'll need to multiply the panel's wattage by how many hours of sun you get every day to understand how much energy it will produce (more on that in the next section).
If you don't have much space, you might want to invest in solar panels with higher power ratings since they're equipped to generate more energy per panel. But they're also more expensive, so bear that in mind if the solar budget for your home is tight.
Some factors, like roof direction, roof shading, the solar inverter you choose, and whether or not you're including a solar battery, could also influence the number of panels you need. These factors, however, are hard to quantify on your own.
The best way to determine the ideal location for your home solar power system and how many solar panels you need is by getting quotes from qualified local solar companies. Solar installers will also be able to give you an idea of the upfront costs of solar for your home and what rebates, incentives, and tax credits homeowners in your area qualify for.
In the meantime, using the steps in this article can give you a rough estimate of how many photovoltaic solar panels you need to power your home with clean, renewable energy.