How many solar panels does your home really need?
Switching to solar energy for your home offers enticing incentives. Lower energy bills, tax credits, and increased property value are some of the immediate benefits. Not only will you save money, but you’ll also contribute to a sustainable future by reducing your carbon footprint and promoting energy independence.
About 85% of residential solar systems today are financed through leases or power purchase agreements, according to the Office of Energy Efficiency and Renewable Energy.
But how much solar does your home need?
To determine a practical estimate of the number of solar panels a home may require, Jake Edie, an adjunct professor at the University of Illinois Chicago, offers a straightforward calculation method.
Let’s say your household uses 1,500 kWh of electricity each month. Here are the steps to calculate the solar panels you’ll need.
Step 1. Review your monthly electric bill: It’s important to determine how many kilowatt-hours of electricity you consume monthly. In this example, this particular home uses 1,500 kWh every month.
Step 2. Convert monthly energy use to daily use: Given 1,500 kWh is consumed per month, to ascertain the daily usage, we need to divide this figure by the average number of days in a month, which is roughly 30.42 days (365 days divided by 12 months).
Hence, the average daily use = 1,500 kWh / 30.42, approximating 49.3 kWh daily.
Step 3. Determine peak sunlight hours: This factor varies based on location and climate. For this example, let’s assume that this home receives an average of about five peak sunlight hours per day.
To calculate the total daily energy production required, divide the daily energy consumption by the number of peak sunlight hours. This gives the amount of energy your solar panels need to produce per day.
Energy production required = 49.3 kWh per day / 5 hours, which equals 9.86 kW.
Step 4. Calculate the number of panels: Lastly, you’ll need to determine the wattage of the solar panels you plan to install. The average solar panel in the US is rated between 250 and 400 watts. For this example, we’ll assume the selected solar panel has a rating of 350 watts.
By dividing 350 by 1,000, we can convert this to kilowatts or kW. Therefore, 350 watts equals 0.35 kW.
To determine the required number of solar panels, we must divide the daily energy production needed by the solar panel’s power output.
Number of solar panels required = 9.86 kW / 0.35 kW per panel, which equals 28.17 panels.
This homeowner will need approximately 29 solar panels to generate enough electricity to match their current usage from the municipal electric company.
Other factors that affect how many solar panels you need
Before trying to figure this all out yourself, it is highly recommended that you seek the guidance of a professional solar installer who can assess your circumstances and provide a tailored solution to meet your needs. They should be certified from the North American Board of Certified Energy Practitioners, which is the solar industry standard.
There are a variety of factors to take into consideration that will help you and an installer determine how many solar panels you need to power your home.
- Solar panel wattage- this will affect how many panels you need. The higher the wattage, the more power a panel can generate.
- Output efficiency- If your roof has limited space for panels, you’re going to want to get the most performance per square inch of panel. In reality, a more efficient solar panel will require fewer panels overall for your home, assuming all other factors are equal.
- Production ratios- The production ratio is expressed as a percentage, with a higher ratio indicating that the PV system is producing a greater percentage of its theoretical output. For example, a performance ratio of 80% means that the system is producing 80% of its rated output in real-world conditions. The higher the production ratios, the fewer panels you might need.
- Panel size– There are three main sizes for solar panels: 60-cell, 72-cell and 96-cell. The 60- and 72-cell panels are more common for residential installations are generally about 3 by 5 feet, or 15 square feet.
- Your location and how much sunlight your home gets- The more hours of sunlight your roof is exposed to, the fewer panels you’ll probably need to install. This is based on the direction, pitch and orientation of your roof, the weather, and how much shade covers the roof. Justin Draplin, CEO of Eclipse Cottages, says “If you live in a really hot climate, then during the summer months, your electrical bill is going to be a lot higher to cool your home versus if you’re in a cold environment, your electrical bills are going to be a lot higher in the winter.”
- Roof type and condition- A home without a complicated roof structure, pitched at a 10-degree angle and south-facing is best for solar panels. The orientation, angle, shape and type of roof will affect the number of panels you can reasonably fit into a given area.
- Cost and budget– While powering your home on solar energy can save you money, it does require a serious investment upfront. The costs to power your home on solar and your budget will determine how many solar panels you can afford. However, many companies offer financing options.
Determining your personal solar goals will help with making these decisions. If you’re wanting to live completely independent and off-grid, you’re going to be investing a lot more than if your goal is to simply reduce your carbon footprint and work towards lowering your energy bill.
Source: CNET