How to Calculate How Many Solar Panels you Need

Are you considering going solar but are not sure how many solar panels you need? You’re not alone. Many people are interested in switching to solar energy but don’t know where to start.

The good news is that it’s not as difficult as you might think. This article walks you through the steps necessary to figure out how many solar panels you need for your home.

Step 1: Calculate Your Energy Needs

This will give you a good starting point for determining the size and number of solar panels you need. To calculate your energy needs, start by looking at your past electricity bills and taking the average.

If you don’t have any past bills, you can calculate your energy needs by doing a home energy audit:

1. Start by going room to room and making a list of all the devices that use electricity in your home. Include everything from lights and appliances to electronics and home office equipment.
2. For each device, note the wattage (you can find this on the label) and the average number of hours you use it each day.
3. Now, calculate the daily wattage for each device by multiplying the wattage by the number of hours you use it.
4. Finally, add up the daily wattages for all of the devices in your home to get your total daily energy needs.

For more information, take a look at this DIY home energy audit.

Step 2: Determine How Many Hours of Direct Sunlight You Get

The amount of sunlight you get will significantly impact the number of solar panels you need. Solar panels work by converting sunlight into electricity, so the more sunlight you have, the fewer panels you will need.

The average home in the United States receives about four hours of direct sunlight per day. However, this number can vary depending on your location.

If you live in a sunny state like California, you may get up to six hours of direct sunlight per day.

On the other hand, if you live in a cloudy state like Washington, you may only get two or three hours of direct sunlight per day.

Step 3: Calculate the Solar System Size You Need

The average home solar system is between four and eight kilowatts (kW). To calculate how many kW you need, divide your total daily energy needs (from Step 1) by the number of hours of sunlight you get (from Step 2).

Solar System Size = Daily Energy Needs / Number of Peak Sun Hours

For example, if you need 30 kWh per day and get 5 hours of sunlight, you would need a 6kW system (30 ÷ 5.)

Step 4: Consider the Amount of Free Space You Have

The final step is to consider the amount of free space you have on your roof or yard.

Solar panels are typically about 65 inches by 39 inches (165.1 cm by 99 cm). So, for every 100 square feet of space, you can fit around four solar panels.

Residential solar panels come in different sizes and wattages that range from 100 to 700 watts.

This means that your 100 square feet can produce anywhere from 400 watts of power (using four 100-watt panels) to 2800 watts (using four 700-watt panels.)

Step 5: Calculate How Many Solar Panels You Need

Now that you have the required system size and considered the amount of free space you have, you can calculate the number of solar panels you need.

Divide your required system size (from Step 3) by the wattage rating of your panels.

Number of Panel = Solar System Size / Panel’s Wattage Rating

For example, if you need a 6,000-watt system and use 200-watt panels, you would need 30 solar panels.

To help make your life easier, we made this table of the most common solar system sizes and how many solar panels they need.