How Many Solar Panels Do I Need?

Calculate How Many Solar Panels You Need for Your Home

With the prices of solar panels coming down and the growing interest in green solutions to our energy needs, it is no surprise that solar power has grown in popularity. For those who are considering adopting solar power, however, the question arises of how many solar panels they need. Contacting a solar panel installer will normally provide the answer, but if you want to calculate for yourself, here are a few steps to help you answer the question, “how many solar panels do I need?”

Determining Your Solar Needs

Whether you are considering solar panels for a residential property, a farm, or a business, there are certain factors that will help you understand your needs:

Annual Electricity Usage

Start by calculating your annual electricity usage. This is the amount of electricity that you consume over the course of a year, measured in kilowatt hours (kWh). This should include the total consumption of electricity in your home or business, including appliances, lights, water heaters, and virtually everything else that uses electricity. The average Canadian household will use 11,135 kilowatt hours of electricity in a year, but this amount can vary drastically by location.

You should also take a moment to consider if your needs will be changing. Will you be adding another freezer or fridge? will you be having children? Do you hope to buy a home entertainment system? Do you intend to buy an electric car?

Situations such as these will significantly add to your monthly usage, so if you foresee any additions that consume a large amount of energy, you will need to take them into account.

Solar Panel Wattage

Although you may not see a difference between solar panels at a quick glance, not all are equally efficient. You will need to know the wattage of the panels that you will be installing. The panel wattage refers to the amount of electricity created by the panel and may range from 250 to 400 watts of power. You can assume an average of 300.

Production Ratios

A solar panel system will have a production ratio indicating the estimated energy output of the system over time in kilowatt hours to the actual system size in wattage. If, for example, you have a 10-kW system producing 16 kWh of electricity in a year, it will have a production ratio of 1.6. The actual rating will vary on how much sunlight you receive.

Calculating How Many Solar Panels You Will Need

The actual calculation for the number of panels you need is simple using this formula:

number of panels= system size/ production ratio/ panel wattage

If, for example, you have 11,000 kW/ 1.6/ 300 W, it will come out to approximately 20 or 25 solar panels. Of course, you can avoid doing the math by reviewing your utility bills to see how much electricity you are using. Simply multiply your energy usage by the number of hours of direct sunlight you receive, then divide by the wattage of the panels you plan to install.

Some of the Factors Affecting the Number of Solar Panels You Need

Although the formula above gives you a quick idea of your needs, there are other factors that you will need to consider. These include:

The Efficiency of the System

There will be many times that your system does not work at peak efficiency. If you have a large snowfall, or a long rainy period, this will affect this system's efficiency. This can be compensated for by having approximately 25% more solar panels than you have calculated.

The best months for solar can vary by location and you will have to account for inconsistencies. For example, what do you do when your system produces excess energy in the summer? How will your solar panels work in the winter? Will you take part in a net metering program with your utility? Do you intend to have solar battery storage to store the excess energy?

Space For Mounting Panels

How much room do you have on your roof for solar panels? Is there enough space for what you will need? If you assume 17.5 square feet per panel and wish to install 20 panels, that will come out to 350 square feet of roof space.

Amount of Sunlight

Perhaps the most obvious factor is the amount of direct sunlight that you will receive. If you don't live in an area with several hours of strong sunlight daily, you will need more panels.

Wattage of the Solar Panels

If you choose lower wattage panels you will require more of them to generate the amount of energy that you need for your home or business. Of course, if you are not planning to replace 100% of your energy usage with solar energy, this may not be an issue.

Average Number of Solar Panels

Because of the number of factors that go into determining your needs, it can be difficult to give any hard and fast guidelines. That said, looking at averages, a home of 1,000 square feet might require 10 to 12 panels. A home of 1,500 square feet may need 16 to 18, a home of 2,000 square feet could possibly use 22 to 24, and a home of 2500 square feet may use 28 to 32 panels, but again this is all dependent on the factors listed above.

If you are looking to add solar panels to your business, a medium-sized business may use approximately 25,000 kilowatt hours each year. With solar panels that produce roughly 250 watts of peak power, and assuming four to six hours of good sunlight each day, one could estimate approximately 70 solar panels.

Final Word

While there are some guidelines that can allow you to estimate the number of solar panels you will need, it is always best to consult with a professional solar panel installer who has the knowledge and experience necessary to be more precise. A solar panel installer will be able to evaluate your needs, as well as the particulars of your region and physical space.

For more information on installing solar panels for your home, farm, or business, please contact us today. Our team of professionals will be happy to assist you.

How Many Solar Panels Do I Need?