This Is How Many Solar Panels You Need to Power Your House
This formula will tell you how many solar panels are needed to meet 100% of your home’s energy demand.
Jackie Lam is a contributor for CNET Money. A personal finance writer for over 8 years, she covers money management, insurance, investing, banking and personal stories. An AFC® accredited financial coach, she is passionate about helping freelance creatives design money systems on irregular income, gain greater awareness of their money narratives and overcome mental and emotional blocks. She is the 2022 recipient of Money Management International’s Financial Literacy and Education in Communities (FLEC) Award and a two-time Plutus Awards nominee for Best Freelancer in Personal Finance Media. She lives in Los Angeles where she spends her free time swimming, drumming and daydreaming about stickers.
- She is the 2022 recipient of Money Management International’s Financial Literacy and Education in Communities (FLEC) Award and a two-time Plutus Awards nominee for Best Freelancer in Personal Finance Media.
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High inflation and the soaring costs of power bills can make powering your home with solar energy quite appealing. And if the allure of going green and saving money has you wanting to go solar, you’ll need to figure a few things before the installer swings by. For one, the number of solar panels to adequately meet your home energy needs.
A common misconception is to gauge how much bang for your buck you’re getting purely based on wattage, says Courtney Corda, co-founder of the California-based solar company Corda Solar. Knowing how many panels you need isn’t just about wattage, but the costs involved in installing, panel performance, location and your usage needs, Corda explains.
Here’s how to figure out how many panels can support your energy needs and what other factors can interfere in your production goals.
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How to calculate how many solar panels you will need
To get a realistic estimate of how many solar panels a home might need, we turned to Jake Edie, an adjunct professor at the University of Illinois Chicago. Edie provided us with a straightforward calculation method.
If you’re curious about how many solar panels your home might require, here’s how you can figure it out, Edie says. Let’s say your household uses 1,500 kWh of electricity each month. Here are the steps to calculate the solar panels you’ll need.
Can solar panels save you money?
Interested in understanding the impact solar can have on your home? Enter some basic information below, and we’ll instantly provide a free estimate of your energy savings.
Step 1. Review your monthly electric bill: It’s important to determine how many kilowatt-hours of electricity you consume monthly. In this example, this particular home uses 1,500 kWh every month.
Step 2. Convert monthly energy use to daily use: Given 1,500 kWh is consumed per month, to ascertain the daily usage, we need to divide this figure by the average number of days in a month, which is roughly 30.42 days (365 days divided by 12 months).
Hence, the average daily use = 1,500 kWh / 30.42, approximating 49.3 kWh daily.
Step 3. Determine peak sunlight hours: This factor varies based on location and climate. For this example, let’s assume that this home receives an average of about five peak sunlight hours per day.
To calculate the total daily energy production required, divide the daily energy consumption by the number of peak sunlight hours. This gives the amount of energy your solar panels need to produce per day.
Energy production required = 49.3 kWh per day / 5 hours, which equals 9.86 kW.
Step 4. Calculate the number of panels: Lastly, you’ll need to determine the wattage of the solar panels you plan to install. The average solar panel in the US is rated between 250 and 400 watts. For this example, we’ll assume the selected solar panel has a rating of 350 watts.
By dividing 350 by 1,000, we can convert this to kilowatts or kW. Therefore, 350 watts equals 0.35 kW.
To determine the required number of solar panels, we must divide the daily energy production needed by the solar panel’s power output.
Number of solar panels required = 9.86 kW / 0.35 kW per panel, which equals 28.17 panels.
This homeowner will need approximately 29 solar panels to generate enough electricity to match their current usage from the municipal electric company. While this calculation may seem straightforward, there are many factors that can affect the effectiveness of solar panels, such as shading, roof orientation, and seasonal variations in peak sunlight.
It is highly recommended that you seek the guidance of a professional solar installer who can assess your circumstances and provide a tailored solution to meet your needs.They should be certified from the North American Board of Certified Energy Practitioners, which is the solar industry standard. CNET also has a well-researched list of best solar companies.
Other factors that affect how many solar panels you need
There are a variety of factors to take into consideration that will help you and an installer determine how many solar panels you need to power your home. Here is a breakdown:
Solar panel wattage
One big part of a solar panel’s performance is its wattage and will affect how many panels you need. The higher the wattage, the more power a panel can generate.
Most residential solar panels have ratings of 250 to 400 watts. The most efficient solar panels on the market are 370 to 445-watt models. The higher the wattage rating, the higher the output. In turn, the fewer panels you might need.
For example, you might buy a solar panel with a listed output of 440 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.
If you don’t have much space, you might want to invest in solar panels with higher efficiency and wattage 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.
Output efficiency
If your roof has limited space for panels, you’re going to want to get the most performance per square inch of panel that you can, explains Corda.
Scientists and technical developers of solar panels have been working hard for decades to try to make each solar cell on the panel able to convert more of the sun’s light to electricity than before, or to make them more efficient, says Corda.
As she explains, currently, the most efficient panels on the market have anywhere from 18% to 22.8% efficiency, with most panels hovering around 20% efficiency. So the higher the efficiency, the fewer solar panels you might need.
In reality, a more efficient solar panel will require fewer panels overall for your home, assuming all other factors are equal.
Production ratios
A production ratio for solar panels helps you determine how much energy you can get from a panel. The production ratio, or performance ratio, is an important measure of the effectiveness and efficiency of a solar system. It compares the actual output of the system to the output it would produce under ideal conditions. This ratio takes into account factors that reduce output, such as temperature, dust, snow, shade, aging of the panels and inefficiencies in the inverter.
The performance ratio is expressed as a percentage, with a higher ratio indicating that the PV system is producing a greater percentage of its theoretical output. For example, a performance ratio of 80% means that the system is producing 80% of its rated output in real-world conditions. The higher the production ratios, the fewer panels you might need.
Panel size
There are three main sizes for solar panels: 60-cell, 72-cell and 96-cell. The 60- and 72-cell panels are more common for residential installations are generally about 3 by 5 feet, or 15 square feet.
Where you live and hours of sunlight
The more hours of sunlight your roof is exposed to, the fewer panels you’ll probably need to install. This is based on the direction, pitch and orientation of your roof, the weather and how much shade covers the roof. It also depends on the time of year and where you live.
In the winter [the solar panel] produces less than in the summer. So your energy production from solar will change throughout the year and then the usage within your home will change depending on what appliances are using electricity, says Justin Draplin, CEO of Eclipse Cottages, a sustainable home technology and development company.
So if you live in a really hot climate, then during the summer months, your electrical bill is going to be a lot higher to cool your home versus if you’re in a cold environment, your electrical bills are going to be a lot higher in the winter.
How much shade your roof gets always plays a factor in how many solar panels you’ll need for your home, Corda says. If your roof is covered by large oak trees or a chimney and gets a lot of shade, this will bump down solar panel output. In turn, you might need more panels to power your home. But if your roof doesn’t get much shade, your solar output will be higher for the same space.
Roof type and condition
The orientation, angle, shape and type of roof will affect the number of panels you can reasonably fit into a given area, explains Corda.
A home without a complicated roof structure, pitched at a 10 degree angle and south-facing is best for solar panels.
That would be an ideal roof for solar because you’ve got it tilted, it’s facing south, and the pitch of the roof is neither flat nor very steep, which is ideal for putting panels on there to capture as much energy from the sun as possible, says Corda. A house with a more complicated roof structure won’t be able to fit as many panels, she adds. For instance, Spanish tile-roofs are considered solar unfriendly and require special attachments.
Cost and budget
While powering your home on solar energy can save you money, it does require a serious investment upfront. The costs to power your home on solar and your budget will determine how many solar panels you can afford.
Currently, the average cost for a home solar panel system is around 3 per watt, according to data from the research firm Wood Mackenzie. Based on this figure, an 8-kilowatt sized system would be 24,000 before any tax breaks or incentives kick in.
Whether you are paying cash or financing, knowing what you can afford will play a factor in how many panels you add to your home.
Annual electricity usage
To know how many panels will meet your energy demand, you’ll need to know your annual energy usage. You can log onto your account online, review statements, you’ll see how many kilowatt hours of electricity you use. You’re going to want to look at your patterns over the course of a year.- if not the last couple of years, says Corda.
Once you have that number, you’ll know how much solar power you need to generate to cover your needs.
Besides recent use, factor in the future energy needs, Corda points out. For instance, do you anticipate purchasing an electric vehicle? Or do you plan on growing your family? Or are you and your spouse going to be working from home more? If so, then your energy needs will go up in the future years. On the flip side, if your teens will soon leave the nest to go to college, then you can expect your energy usage to taper off.
Your personal solar goals
Determining your personal solar goal is figuring out what you want to achieve with your solar panel addition. Living completely energy independent and off the grid would mean more solar panels. If you want to power your whole house, you have to really oversize it to make sure you have enough power in the winter, even though you’re going to be over producing in the summer, says Draplin.
Adding battery storage will also play a factor in how many panels you need. With solar battery storage, you can essentially bank energy and store it for later use when you’re producing excess energy.
If your goal is to lower your energy bill or reduce your carbon footprint, then maybe you won’t need as many panels, says Draplin.
Figuring out the number of solar panels you need is only part of the equation. Learn more about the benefits and costs of home solar from CNET:
Solar panel FAQs
Can I run my house on solar power only?
The simple answer is: Yes, you can power a house entirely on solar power. To meet your energy ends, you’ll want to factor in a handful of variables: the size, pitch and orientation of your roof, the size of panels you’d like to install, the amount of shade, output efficiency and wattage. Plus, you want to figure out current and future usage needs, and whether you want your entire home to be powered on solar energy or just part of it.
Trina Solar Monocrystalline (490W) TSM-490
Trina solar TSM 490 watts is a high profitable monocrystalline solar panel. Trina Solar TSM helps the user to overcome the unaffordable electricity bill. Trina monocrystalline panel is Compatible with off-grid and on-grid solar inverters and it’s equally beneficial for commercial and residential places as well. Trina Solar has a company official 25 years’ performance and 10 years’ replacement warranty.
Reliability:
Over 30 in-house tests (UV, TC, HF.
Increased module robustness to minimize micro-cracks.
PID resistant and free of snail trails.
ELECTRICAL DATA @ STC:
Peak Power Watts-PMAX (Wp): 490
Power Output Tolerance-PMAX (W)P: 0 ~ 5
Maximum Power Voltage-UMPP (V): 42.4
Maximum Power Current-IMPP (A): 11.56
Open Circuit Voltage-UOC (V): 51.3
Module Efficiency ηm (%): 20.5
Reviews
MAECENAS IACULIS
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ADIPISCING CONVALLIS BULUM
- Vestibulum penatibus nunc dui adipiscing convallis bulum parturient suspendisse.
- Abitur parturient praesent lectus quam a natoque adipiscing a vestibulum hendre.
- Diam parturient dictumst parturient scelerisque nibh lectus.
Scelerisque adipiscing bibendum sem vestibulum et in a a a purus lectus faucibus lobortis tincidunt purus lectus nisl class eros.Condimentum a et ullamcorper dictumst mus et tristique elementum nam inceptos hac parturient scelerisque vestibulum amet elit ut volutpat.
Trina Solar Monocrystalline (490W) TSM-490
Trina solar TSM 490 watts is a high profitable monocrystalline solar panel. Trina Solar TSM helps the user to overcome the unaffordable electricity bill. Trina monocrystalline panel is Compatible with off-grid and on-grid solar inverters and it’s equally beneficial for commercial and residential places as well. Trina Solar has a company official 25 years’ performance and 10 years’ replacement warranty.
Reliability:
Over 30 in-house tests (UV, TC, HF.
Increased module robustness to minimize micro-cracks.
PID resistant and free of snail trails.
ELECTRICAL DATA @ STC:
Peak Power Watts-PMAX (Wp): 490
Power Output Tolerance-PMAX (W)P: 0 ~ 5
Maximum Power Voltage-UMPP (V): 42.4
Maximum Power Current-IMPP (A): 11.56
Open Circuit Voltage-UOC (V): 51.3
Module Efficiency ηm (%): 20.5
Reviews
MAECENAS IACULIS
Vestibulum curae torquent diam diam commodo parturient penatibus nunc dui adipiscing convallis bulum parturient suspendisse parturient a.Parturient in parturient scelerisque nibh lectus quam a natoque adipiscing a vestibulum hendrerit et pharetra fames nunc natoque dui.
ADIPISCING CONVALLIS BULUM
- Vestibulum penatibus nunc dui adipiscing convallis bulum parturient suspendisse.
- Abitur parturient praesent lectus quam a natoque adipiscing a vestibulum hendre.
- Diam parturient dictumst parturient scelerisque nibh lectus.
Scelerisque adipiscing bibendum sem vestibulum et in a a a purus lectus faucibus lobortis tincidunt purus lectus nisl class eros.Condimentum a et ullamcorper dictumst mus et tristique elementum nam inceptos hac parturient scelerisque vestibulum amet elit ut volutpat.