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How Many Solar Panels You Need to Power a Home: A Comprehensive Guide

Solar panel systems and installation costs have become more cost-efficient over the last few years. Affordable, high-efficiency solar panels and batteries have made going solar-only for residential use more practical. It’s never been easier to help the environment and cut energy costs.

However, you should research before buying a system and an array of panels. Buying too many panels can be a waste of money while buying too few could make your investment unprofitable or force you to pay your installer to add more panels a second time.

Learn everything you need to know about solar panel systems and how many solar panels it takes to power a home efficiently.

How Much Power Can a Solar Panel Produce?

Watts (or wattage) is the unit of measurement to determine the amount of energy generated by solar panels. In today’s market, the most popular solar panels for homes can generate anywhere from 250 to 400 watts of power.

It is difficult to predict how much energy your particular solar panel system would produce because of the inherent variability of the technology.

However, you can evaluate your solar panel system’s potential output using a few basic benchmarks.

Calculating Solar Panel Output

1. Daily solar panel output

Use this formula to estimate the daily electricity output of your panels in kilowatt hours (kWh):

(The square meter size of one panel x 1000) x (the average solar panel’s efficiency yields (percentage as a decimal)) x (the average hours of sunshine in your area) / 1000 = Solar panel output


  • The size of the solar panel is 1.6 square meters (approx. 17.5 square feet)
  • The efficiency of the solar panel is 20%.
  • The average daylight hours in a day are 6 hours.

(1.6 x 1,000) x (0.2) x (6) / 1000 = 1.92 kWh per day

Remember that sunlight hours are somewhat low in the winter (nearly half of what they are in July), and they fluctuate widely throughout the year.

2. Monthly solar panel output

To get the monthly total, take the daily solar panel output figure and multiply it by 30.

(1.92 x 30) = 57.6 kWh per month

3. Solar panel’s wattage per square foot

Calculating the solar power per square foot is straightforward:

(Solar panel wattage) / (size of the panel)


(250W) / (17.5sq. ft) = 14.29 watts of solar power per square foot

4. Solar panel kWh per square foot

Calculating solar kW per square foot requires converting our power input into energy output. One kilowatt-hour is equal to 1,000 watts (or joules) of energy used for an hour. You would multiply the amount of electricity consumed in watts by the hours used to convert watts to kilowatt-hours. After that, divide by 1000.

kWh = (watts × hrs) ÷ 1,000 

For example, to find the kWh of 1,500 watts for 4 hours:  

kWh = (1,500 × 4) ÷ 1,000

kWh = 6 

Solar Panel Efficiency

Determining how many solar panels you need to power a home will depend on their efficiency. The wattage of your solar panels will tell you how much energy they can generate, while their efficiency will tell you how much power they can get from the sun.


If your solar panel has an efficiency of 20%, it can convert 20% of the sunlight that hits the photovoltaic (PV) modules into usable energy. Several elements might increase or decrease efficiency:

Shade — You should avoid shade at all costs. You can accomplish this by correctly pruning trees and placing panels to avoid shading from surrounding buildings. 

Pollutants — Dirt, smog, and dust are all detrimental to solar panels and can speed up their deterioration over time. You can routinely maintain panels by hiring a professional cleaning service.

Weather conditions — There’s not much you can do about a heavy cloud cover or snowfall, as they’re natural phenomena. However, remember that solar panels can produce power even on overcast days.

Region — Where you live affects how much energy you can generate using solar panels. The more light can reach solar panels, the more power they can convert. However, even northern areas with overcasts can still benefit from solar.

Layout — The output is affected by the orientation of your solar panels. Depending on your latitude, the optimal placement for a solar array is either south or west. You can maximize your panel’s energy output by positioning them to face the direction that gets the most sunshine. 

Electrical system — The rest of the system will impact how much energy the solar panels can produce. Each component, such as the inverter, wires, and charge controller, affects the efficiency when using a battery.

How Many Solar Panels Do You Need?

On average, a solar panel can convert 250 watts per hour of sunshine into usable energy. If your panels receive at least 6 hours of sunlight each day, you may expect to generate about 1.5 kWh of power daily, equivalent to roughly 45 kWh per month. The quantity of sunshine your panel receives and your location will play a role in these estimates.

So, how many solar panels does it take to power a house?

If a single solar panel can produce 45 kWh per month and the average American home consumes around 900 kWh monthly, you would need at least 20 solar panels.

However, in most instances, you’ll need more than 20 panels because it’s highly improbable that they’ll get 6 hours of sunlight daily. In general, if you’re asking:

  • How many solar panels do I need for a 1000 sq ft home?
    • You’ll need between 10-12 panels.
  • How many solar panels do I need for a 2,000 sq ft home?
    • You’ll need between 20-24 panels.
  • How many solar panels do I need for a 2,500 sq ft home?
    • You’ll need around 30 panels.

However, each property has unique aspects, and these characteristics must be considered before concluding how many solar panels you need. Once you make these determinations, you can calculate this answer with a high degree of accuracy. 

However, before committing to a number, it’s best to get an expert’s opinion. EMT Solar & Roofing can help you with a free estimate. 

How to Calculate How Many Solar Panels You Need to Power Your Home

Starting with these basic assessments can help you estimate the cost-effectiveness and other important factors in maintaining a solar-powered house:

Step 1. Determine your monthly electricity use.

To begin, calculate how much solar energy you’ll need to generate to power your entire home. You’ll need to know your typical monthly electricity use for this. Review your current energy bill to learn how much electricity you use each month.

However, according to the US Energy Administration, typically, a: 

  • One-bedroom apartment averages a use of 900 kWh per month
  • Three-bedroom home averages a use of 3,000 kWh per month
  • Five-bedroom home averages a use of 4,300 kWh per month

Due to seasonal variations in energy consumption (such as heating during the winter and air conditioning in the summer), your annual energy usage is the best indicator of how many solar panels you need.

It’s helpful to gather last year’s electric bills to get a clearer picture of your energy usage.

Your solar installer can help determine how much energy your panels will need to produce each month to meet your needs.

As noted above, solar energy generation and monthly use potential will fluctuate with the seasons. With the reserve capacity of modern household solar battery storage, you can rest easy knowing that your home will always have access to reliable electricity. With solar batteries, you can save the extra energy generated by your solar panels on days with more sunlight.

When there isn’t as much direct sunlight, mainly when the days are cloudier, solar batteries store energy so you can keep your complete house running without having to rely on the grid.

Step 2. Determine how much solar energy your region can generate.

The next step after discovering your monthly electricity consumption is to learn how much sunshine your area receives.

Whether or not solar panels provide enough energy to run your entire home all year long depends on the local climate.

This is typically quantified by “peak sun hours,” when the sun is at its brightest in your location.

One kilowatt of solar panels will generate its power based on the number of hours of peak sunlight received each month. Consequently, if your house gets an average of 140 hours of sunshine each month, a 1 kW solar array will generate 140 kWh per month.

Sustaining a home solely on solar may be challenging during the winter months for people who live in colder, cloudier places. While large areas of the United States could go weeks without seeing clouds, other climates, especially those in the northwest, can go months with heavy cloud coverage.

Depending on the weather and other conditions unique to your home and lifestyle, you may need to rely partially on your utility provider for power. However, it is possible to go entirely off the grid in many regions within the US.

Step 3. Calculate how many panels you will need.

To get the required system size in kilowatts (kW), divide your monthly kWh usage by your area’s peak sun hours. Here’s a rough estimate for the typical American house:

900 kWh used / 143 monthly peak sun hours = 6.23 kW of solar power

Next, multiply the solar system’s kilowatt output by 1,000 to get the number of solar panels you’ll need. Let’s go back to the original example:

6.23 kW x 1,000 = 6,230 watts

Then, divide the system’s total wattage by the maximum power output of the solar panels you plan to use. For this example, we’ll use 250-watt output. 

6,230 watts / 250-watt panels

In this case, 25 solar panels are needed to meet energy needs.

What Size Solar System Do You Need? 

The size of the solar panel array is a significant factor in determining how many solar panels you need to power your home, especially if the roof has an unusual form. Here are some things to think about:

  • If your roof is relatively large, you can purchase larger panels (at a cheaper cost per panel) to get your desired energy output.
  • A lesser number of high-efficiency panels may be the best long-term investment if your usable roof space is restricted or under partial shade. If your energy needs grow in the future, you can always install more panels.

Generally, covering the necessities for a typical day’s household needs should be your bare minimum goal. Even though the cost of solar panels for 2500 sq ft home roofs are becoming more reasonable, installing more solar panels may not be worthwhile if your regular daily electricity demand is only 20 kWh but spikes to 30 kWh once in a while. 

This is why it is essential to discuss your options with your installer. We recommend that most homeowners strive for a system size of at least 6.6 kW when installing a solar system.

Of course, it is sometimes simpler to speak with a professional when planning your solar system sizing. Your contractor can help you determine the size of your solar panel installation and the best solution based on your roof’s structure. 

Trust EMT Solar & Roofing with Your Solar Panel Needs

EMT Solar & Roofing is your one-stop shop in New Jersey for expertly installed solar panels. Rather than leaving you to navigate the process on your own, we will be there to guide you through it. 

When figuring out “how much do solar panels cost?” we recommend scheduling a meeting with us to ensure the system fits within budget, roof space, and energy offset goals.

Get a free estimate today to find out how to make your roof sustainable.