The following three factors will enable you to calculate the number of solar panels you need for your home:
- Your electricity bill.
- The amount of sunlight at your location.
- The output of the solar panel you select.
The amount of space on your roof may also come into play, but we will discuss this later in the article. For now, here is a brief overview of how you can calculate each of the three factors to get an answer:
Your Electricity Bill
The first step is to determine the electricity consumed by your household. For best results, try to calculate the electricity consumption in one year. If your electricity bill does not fluctuate wildly, you may also get the kWh figure by looking at your monthly bill.
According to the U.S. Energy Information Administration, the average residential customer in the United States uses 10,649 kWh a year. The figure translates into 877 kWh per month. You can find the required kWh figure in your latest energy bill. If you can’t find the kWh reading, subtract the previous reading from the current reading.
For the sake of this article, let’s assume that your average electricity bill is 900 kWh per month.
Due to variations in peak sunlight hours in Winter and Summer, it’s practical to calculate your monthly electricity bills based on an average for 12 months. It makes sense because you don’t want to end up with low or very high estimates.
The Amount of Sunlight at Your Location.
The amount of sunlight at your geographical location also determines how many home solar panels you need. For solar installation in Monterey CA, you may need fewer solar panels than a similar installation in Seattle.
You often require fewer solar panels in Monterey because the region enjoys almost 267 sunny days in a year. Compare these figures to Seattle, where you only get 152 sunny days. Since solar panels help store energy from the sunlight, warmer areas use fewer solar panels than colder regions.
For calculations, use the average sunlight hour per day in your city. Here is a table that shows the average sunlight hour per day in each U.S. state. You can use the figure for your state. For solar installation in Monterey CA, let us use 5.38 hours, which is the average for California.
Calculate the Amount of Energy Your Home Will Need
Once you’ve figured out the monthly electricity bill and the average sunlight hour per day, it’s time to calculate your home energy needs. This is needed to determine the number of home solar panels for your home.
Plug the two figures in this formula:
Electricity consumption per month /(average sunlight hours per day x 30)
In this example, the electricity consumption is 900 kWh per month, and the average sunlight hours per day is 5.38. Multiply 5.38 by 30 to get a monthly figure.
Amount of Energy Your Home Needs = 900 /(5.38 x 30) = 5.58 kW.
It means that you will need 5.58 kW of the solar system to meet your energy needs. In other words, we can also say that we need a (5.58 x 1000 watts) 5580 watts solar system.
The Output of the Solar Panel
The third critical factor that determines the number of home solar panels is the solar panel output. There is a wide variety of solar panels in the market ranging from 200 kWh to 370 kWh. The average solar panel has an output of 265 kWh per panel.
The final output produced by a solar panel depends on efficiency. Under normal conditions, solar panel efficiency of 15% with one square meter produces 150 watts. For this discussion, assume that the output of a solar panel is 300 watts per panel.
Here is the formula for calculating the number of home solar panels you will need:
Number of solar panels = Energy Your Home Needs/output per panel
= 5580 watts/300 kWh per panel
= 18.6 solar panels.
A typical home needs between 20 and 25 solar panels to offset the entire electricity bill of an average home. However, a solar contractor can also give you a better idea after inspecting your premises.
Here is a recap:
- Calculate the kWh per month.
- Calculate the amount of sunlight per day in your location.
- Plug these two figures in the formula: Amount of Energy Your Home Needs = kWh / daily sunlight x 30.
- Convert the result to watts by multiplying the result by 1000.
- Determine the output per panel for your desired solar panels.
- Use this formula to find the number of solar panels:
Number of solar panels = Energy Your Home Needs/output per panel.
Before shopping for solar panels, you should also consider the amount of usable roof space. Generally speaking, a roof with a 30-degree pitch is ideal for residential solar installation in Monterey CA. Depending on the roof structure, you may need additional solar panels to achieve the desired output.
Considering the peak sunlight hours in various parts of the United States and weather conditions, an 8 kW solar system needs 406 square feet of space. Lower power panels may require 490 square feet, while high power panels can produce desired results using 358 square feet of space.
If you’re using solar panels to charge individual products, the required number of solar panels can differ considerably. For instance, you may need ten solar panels to charge an electric car and an outdoor hot tub. Similarly, a heated swimming pool uses almost eight solar panels.
In contrast, a single air-conditioning unit often uses less than one solar panel. The entire central air conditioning system may take only three solar panels to power it.
Remember that these are sample figures based on nationwide trends, which may differ based on your specific needs for solar installation in the California, Monterey Bay area. Therefore, you should discuss these details with a solar contractor in your area.