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How to Easily Calculate Your Solar System Size

July 20, 2023

Do you know how to calculate your solar system size and other requirements? If you’re like many property owners, the answer is a resounding no! Despite its popularity, solar arrays are still a bit of a mystery to many. However, you can determine the right panel type and number with a few simple steps.

To calculate your solar system size:

  • Understand your power requirements and energy goals
  • Assess your location including its energy production
  • Consider panel efficiency
  • Calculate panel size and number of panels needed

This is just a quick rundown of the steps needed to calculate your solar system size and other vital details. To help you find the right solar array system for your property, keep reading! Added details about each of these steps can ensure you make the right choice. This information can also help when it’s time to speak to a solar panel installation technician near you.

how to calculate your solar system size

How to Calculate Your Solar System Size and Other Details

To calculate the size of a solar system you need to consider more than your energy consumption and location. Here's a general outline of the process:

Understand your electricity consumption

Start by reviewing your electricity bills. This information helps you understand your average monthly and annual energy needs.

To read the bill, note the total kilowatt-hours (kWh) used over a specific period, such as a full year. This will give you an idea of your energy needs. You might need to add every month’s kWh to get your annual usage.

Determine your energy goals

Decide how much electricity consumption you want to offset with solar power. For instance, some homeowners want panels to provide all electricity usage. On the other hand, some might only need panels to offset some of their energy consumption.

Assess your location

The amount of sunlight your location receives throughout the year plays a crucial role in sizing your solar system. Remember, solar panels work by capturing sunlight and converting it into usable power. In areas without much sun, you might need more panels on your property. This allows the system to capture all the sunlight needed for your energy needs.

Along with the number of sunny days in your area, you need to consider your property’s sun exposure. Trees, lots of dust in the air, tall buildings or billboards, and other features block sunlight to solar panels. A solar panel installer can help with this step.

Consider panel efficiency and losses

Solar panels have an efficiency rating. This rating indicates how much sunlight they can convert into electricity. When considering this rating, take into account anything that might reduce that efficiency. That includes excessive shade and other factors mentioned above.

Account for system degradation and future needs

Keep in mind that solar panels gradually degrade over time. In turn, they produce less energy, usually at about 0.5% to 1% annually. In other words, your panels might produce 1% less energy every year. In turn, 20-year-old panels might work at 80% efficiency.

With this mind, consider your long-term solar investment and not just how much energy they produce when first installed. Additionally, don’t forget potential changes in your energy consumption in the future. If you might choose larger appliances or upgrade your AC system, you might need a more effective solar array.

Other factors to consider

There are other factors to consider when it comes to solar panel basics. These include your property’s roof orientation and tilt. A steeply sloped roof often means less sun exposure throughout the day.

Also, remember local regulations. Some cities or counties might restrict solar panels for various properties. Additionally, some might not allow you to disconnect from the power grid altogether. Consequently, you might not need as many panels as you expected.

Use our solar calculator

Now that you know a bit more about how to calculate your solar system size, it’s time to use our solar calculator! Online calculators can figure your current energy consumption versus solar power produced. These can also tell you how many panels your property needs for adequate energy. Using our calculator then makes it easy to see all the advantages of going solar on your property.

installing solar panels

How Much Energy Does the Average House Use?

If these steps seem too complicated or you’re not sure how to read your electric bill, consider some national averages. In the United States, the average residential home consumes 10,417 kWh annually. That number drops down to 868 kWh per month.

However, homeowners should remember to adjust this number according to your own needs. For instance, in tropical or desert areas, you might run the air conditioner far more often than usual. In extremely cold climates, this is true of the home’s furnace!

Also, don’t overlook the power used by computers, gaming systems, and oversized appliances. This includes any you might buy in the future. If you know you have more high-end electronics than average, your power consumption is also probably higher than usual.

How Big Is a 10kw Solar System?

First, note that most solar panels measure 300W to 400W. Also, one kilowatt equals 1000 watts. In turn, you might need anywhere from 25 to 30 panels or more to create a 10kw solar system. This 10kW solar system might also need 600 to 700 square feet on a residential rooftop.

Also, note that solar panel sizes vary based on manufacturer, age, and overall power. Some panels are more compact than others, affecting the overall system size. In turn, your home might not accommodate a standard 10kw solar system. However, higher-quality micro panels might fit on a residential roof and provide the power your property needs.

How Long Does It Take for Solar Panels to Pay for Themselves?

The payback period for solar panels, or the "return on investment" (ROI) period, depends on various factors. These include the initial cost of the solar system, available incentives, electricity rates, and the amount of energy it produces. Generally, the payback period for residential solar panels ranges from 5 to 15 years.

System Cost

Consider the total cost of installing solar panels, including equipment, labor, permits, and additional components. Obviously, these costs significantly impact the payback period! Higher upfront costs mean a longer payback period.

Incentives and Rebates

Solar incentives, tax credits, and rebates significantly reduce your initial solar cost. In turn, these incentives affect the payback period. The greater the incentives, the lower your installment costs. Your panels then begin paying for themselves much sooner.

Electricity Rates

The cost of electricity from your utility company affects how much money you save with solar panels. Higher electricity rates usually lead to a shorter payback period. In other words, more expensive electricity means more savings with solar!

Energy Production

The amount of electricity your solar panels generate determines how quickly they pay for themselves. This energy production depends on your location, sunlight exposure, panel efficiency, shading, and orientation. A more efficient and well-placed system produces more electricity. In turn, it reduces your payback period.


If you financed your solar system, this could influence the payback period. Paying upfront will typically yield a shorter payback period. On the other hand, financing with ongoing payments means a longer wait time before the panels pay for themselves.

Energy Consumption

The amount of electricity your household consumes directly affects how much is offset with solar power. Higher energy consumption means more potential savings and a shorter payback period.


As solar technology advances and costs continue to decrease, the payback period for solar installations is becoming shorter. This makes solar energy an increasingly cost-effective and sustainable investment for many homeowners.

solar panels on a roof top

Do You Get Money Back From Using Solar Energy?

Energy cost savings from solar panels is the best way to earn money from their use. Also, federal tax incentives can lower your installation costs. These incentives allow you to claim a credit against your federal tax bill for a portion of your installation costs.

Net metering also means money in your pocket from solar energy production. This arrangement credits your power bill according to the energy your panels produce. In some cases, excess credits might carry over to the next month. In other areas, your power company might send you a check for that extra energy.

Additionally, solar panels often increase property values, usually by 4% or more. However, many states waive increased property taxes on that added value. In other words, you won’t pay a higher tax bill even though your property is worth more after solar installation.

Remember that your solar panel installation contractor can also explain current incentives, rebates, and other factors. In turn, you’re sure to enjoy maximum financial benefits by investing in solar.

Are Solar Panels Worth It?

Most homeowners would say that solar panels are worth the cost! Note a few advantages to solar panel investment:

  • Solar panels generate electricity from sunlight, reducing your reliance on electricity from the grid. If you have high electricity bills, solar panels can lead to substantial energy savings over time.
  • Generally, solar panels have a payback period of 5 to 15 years. After that, you can enjoy free or reduced-cost electricity for the rest of the system's lifespan (typically 25-30 years).
  • Solar is a clean and renewable energy source, reducing greenhouse gas emissions and your carbon footprint. Installing solar panels can contribute to a more sustainable future and help combat climate change.
  • Generating your electricity with solar panels provides a degree of energy independence, as you become less reliant on the fluctuations of energy prices and potential power outages.
  • Solar panels can increase the resale value of your home, making it more appealing to potential buyers. Many homebuyers are interested in energy-efficient features like solar panels.
  • Solar panels have a long lifespan and require minimal maintenance. Over time, the cost of electricity from solar panels is generally lower than utility rates, resulting in long-term savings.

A Word From Our Solar Crew

The team here at Solar Savings Calculator is happy to explain how to calculate your solar system size. Remember to use our online calculator for best results! Also, you can contact us to find a solar installation contractor near you. Every contractor we work with guarantees their installations for quality. To find out more about how to save with clean, green solar, contact us today!


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