Solar accounted for 15.9% of electricity generated by renewable sources in 2022, making it one of the most popular methods of generating clean electricity. If you’re at the beginning of your solar journey and feeling slightly baffled, rest assured that every homeowner has been through this. After all, it’s easy to lose track of all the details despite their importance.
Determining the right number of solar panels and the appropriate budget for the system requires a detailed estimation. That’s where search queries such as “How many solar panels do I need?” come in. Use tips from our article to analyze your needs and precisely evaluate your future budget for switching to green energy.
The average price of solar calculator panels in Illinois is approximately $3.05/W, but it varies widely depending on the manufacturer and system parameters. Those who want to estimate the potential systems’ price beforehand should use a solar panel cost calculator for a rough estimation. Here is how it looks:
As you can see, using such a solar panels calculator is pretty simple. All you need to do is take a notebook and pen (Google Docs will be also fine), and a calculator, and give yourself 10-20 minutes to calculate.
The easiest way to determine your average electricity usage is to examine electricity bills for 12-24 months. If you just moved into the new place and don’t know your typical usage, monitor your consumption for at least 3-4 months. That way, you can study your habits throughout multiple seasons, which will be a crucial part of solar panels calculator estimations.
You should know your average electricity consumption during at least one peak period: summer or winter. During those periods, people use air conditioning to heat or cool the air. They also usually set their freezers to maximum settings to prevent their food from accidentally spoiling. If you don’t use information about your peak consumption in the solar panels calculator, you may not have enough electricity to power your appliances during a potential outage.
Meanwhile, Chicago’s spring and fall temperatures are usually mid-range, between 55°F and 65°F. During those periods, people don’t use air conditioners that much. There are also a lot of fresh vegetables available at any supermarket, so people are less reliant on freezers. That’s why monitoring your electricity consumption during peak periods is crucial. It allows you to set proper information in the solar panel power calculator.
According to the U.S. Energy Information Administration (EIA), the average American household uses almost 11,000 kWh of electricity annually (or about 920 kWh per month). We’ll round this up to 1,000 in our solar power panels calculator since it’s better to overestimate the household’s daily electricity usage rather than understate your needs and purchase a system that doesn’t fit.
If you want to be fully independent, your solar output should exceed your current needs. So, the next step in your solar panel power calculator is to find your approximate daily usage. If you use 900 kWh/month, your approximate daily consumption is 30 kWh/day. To play it safe, you can overestimate it to 35 kWh per day.
Illinois receives 4 daily hours of peak solar energy during summer, while this parameter falls to 1,5 hours during winter. Peak sunlight hours are crucial for the solar panel savings calculator since you’ll get full power from your system. During morning and evening hours, your panels generate less power than the manufacturer states as the output.
In this solar panel output calculator step, you will divide your daily energy usage by the sunlight hours to find the required solar system size (in kW). The formula looks like this:
System Size (kW) = Daily usage (kWh)Sunlight hours
On average, Illinois gets 6,5-7 hours of sunlight daily. If your daily electricity consumption is 33 kWh, you need to divide 33 by 7, resulting in 4,76 kW. The solar panel energy calculator results show that you need a system with at least 4,8 kW output. However, it’s better to play it safe and install the more powerful 5.5-7 kW system.
It’s better to overestimate the kWh calculator for solar panels since manufacturers usually describe only the maximum output during ideal conditions. Unfortunately, Illinois often has less-than-perfect weather with wind, clouds, rain, and snow. It means that most of the time, panels produce slightly less than expected. So, when looking for a result in the search query of “how many solar panels do I need: calculator”, it’s better to overestimate your needs and put in 2-3 panels more. That way, you can be sure you’ll have enough electricity to power your home even during blizzards.
Solar systems work for 15-20 years; during that time, your power needs may grow, while panels might slightly lose capacity. So, while you use a calculator for solar panels, it’s better to overestimate your needs rather than lower them.
This step is not obligatory, but you may use the “how many solar panels” calculator if you have a limited roof space. Most panels produce 300-400 watts under ideal conditions (a sunny midday that is not too warm or cold). Considering cloudy and windy Illinois weather, it’s safe to assume that the average panel will produce 250-350 watts.
Considering that you want a 7 kW system, your “solar panels needed” calculator will look like this:
Number of panels = System size (Wh)The average panel output (W)
Let’s suggest you install a 7 kW system, where each panel produces 300 W. Your solar panels size calculator will look like this: 7000 ÷ 300, meaning that you’ll need 24 panels to achieve this result. If your home has a small roof and you don’t want to place panels in the backyard, look for more powerful panels. If each panel produces 400 W, your solar panels calculator will look like this:
7000 Watt ÷ 400 Watt=17,5 (panels)
You can round it up to 18 panels. Be aware that powerful systems are usually more expensive than average ones. In this case, the solar panel ROI calculator may show that you need more time to return your investments.
While deciding what size of panels you need and where to place them, consider your energy goals, potential roof space, and battery storage. You will need all this info for your solar panels calculator. At first, you need to decide whether the system should cover 100% of your usage or just supplement grid power. If you want to go off-grid, add an extra kWh to your solar panels kWh calculator. You may need 2-3 panels more to ensure that the chosen system will meet your future needs.
Keep in mind that solar panels are not as small as laptops. The average panel requires approximately 18ft² of space, and some roofs may not have enough space to fit all panels. That’s why a great solar panels calculator often asks about roof space to accurately assess potential available space. In this case, you may mount them onto the walls or place them in the backyard. The professional installer team will help you determine the best place and angle to set your future system.
If you want to know the approximate space needed, use our “How many solar panels can I fit on my roof” calculator. It helps you to understand the desired system configuration even before you contact solar experts. During our estimations, we use 18ft² as the average panel size.
| System Size | 300 W Panels (sq. Feet) | 340 W Panels (sq. Feet) | 360 W Panels (sq. Feet) | 400 W Panels (sq. Feet) |
| 4 kW | 240 | 212 | 200 | 180 |
| 7 kW | 420 | 370 | 350 | 315 |
| 9 kW | 540 | 475 | 450 | 416 |
Last but not least, consideration of the cost of solar panels calculator is whether you need battery storage. If you want to go completely off-grid, you must purchase powerful and capacious batteries, which may add another $7,000-$15,000 to the final cost. If you want batteries that support you as the emergency power supply during outages, it may be enough to purchase 3-4 kWh batteries, which cost almost half as much. If you have an on-grid system, you may not add battery cost to solar panels return on investment calculator.
A solar panel calculator is a vital tool that helps you accurately plan your future solar energy system. It helps you to determine the ideal number, size, angle, and placement of panels to maximize energy production. By using this tool, you can save money, reduce waste, and ensure your investments deliver the best possible results.
Looking for a reliable solar panels calculator to estimate your future project? Get your free solar quote and estimate the optimal system size, panels’ output, and potential budget in a matter of minutes!