How Many Solar Panels Do I Need?
One of the most common questions photovoltaic (PV) installers get during early consultations with customers is, “how many solar panels do I need for my home (or business)?” It’s a natural question since the number of PV panels directly impacts the total cost of the installation – not to mention variables like:
Monthly savings
Carbon offsets
Payback periods
However, it can be challenging to explain technical terms like insolation, voltages, or kilowatt-hours to a homeowner used to thinking in dollars and cents. If you’ve faced this situation before, use the guide below to make the solar consultation process easier to explain – and easier for customers to understand.
How Many Solar Panels Are Needed To Power A House?
Every home is different, making it difficult to provide a universal answer that applies in all situations. But here are some useful guidelines to keep in mind:
The U.S. Census Bureau reports that the average single-family home is just over 2,300 square feet. This is a useful metric. But it’s not nearly as important as the next two points.\
According to the U.S. Energy Information Administration, the average American home consumes nearly 900 kWh of utility electricity each month.
The Solar Energy Industries Association (SEIA) estimates that the average size for a residential PV installation is 5 kW (or about 15 – 35 panels depending on the wattage of each module).
5 kW is a good baseline. And it’s a number most homeowners will understand. But still, it’s important you correctly size every solar system so that it covers the amount of energy that customer uses – both today and tomorrow.
To understand what that involves, keep reading.
How To Determine The Number Of Solar Panels Needed
When sizing a residential solar system, below are five of the most important variables that should factor into the decision-making process.
1. The Homeowner’s Energy And Savings Goals
Adding just a single solar panel can help generate monthly electric bill savings. Installing more PV modules results in higher savings. So it’s important you consult with each customer to determine their energy and savings goals in advance.
For example, do they:
Want enough solar capacity to cover 100% of their electricity needs?
Plan on using net metering to sell excess power to their utility provider?
Need on-site batteries to store daytime solar energy for nighttime use?
Clearly defining these goals is crucial before moving on to the next steps.
2. Current Household Energy Usage
With energy and savings targets in place, you’re now ready to analyze the customer’s historic electricity consumption. Most homeowners focus on the dollar amount of past electric bills. But what matters more is the kilowatt-hours consumed over the past year.
The higher their electricity usage, the more solar panels you’ll need to install to cover that energy consumption.
3. Power Needed For Common Appliances
The next step involves developing a clearer picture of the customer’s energy needs moving forward. Historic analysis already takes into account whatever power-hungry appliances already exist in the home. But with growing families and more electronic gadgets, it’s likely those power needs will grow over time. In fact, “electrifying” one’s home is very common among solar power customers, whether they replace:
Gas-guzzling cars with electric vehicles (EVs)
Natural gas furnaces with electric alternatives
The goal here is to power more appliances with free energy from the sun instead of with utility electricity made from fossil fuel. In talking with customers, it helps to show charts and infographics so that they can better understand the effect that future purchases will have on their energy production and needs.
In addition, many customers can also make energy efficiency improvements throughout their homes. Swapping out incandescent lightbulbs with LEDs, for example, helps to reduce electricity consumption. And this allows you to install a slightly smaller solar panel system to cover that homeowner’s energy needs.
4. How Many Hours Of Sunlight Does The Area Receive?
Geography can have a huge impact on PV panel performance, with a state like Arizona receiving more direct sunlight than someplace like Massachusetts. The same is true of the changing seasons, which is why you want a year’s worth of electricity bills – and not just the past few months.
Fortunately, the National Renewable Energy Laboratory (NREL) publishes several solar radiation resources to help you determine the average amount of sunlight for each geographic region throughout the year. And these charts can help make your own sizing estimates far more accurate.
However, there is still one more piece of the puzzle.
5. Things That Can Impact Solar Panel Efficiency
Solar PV panels are tested in ideal laboratory conditions. But the average home exists in the real world where constant exposure to UV light is impossible. And you’ll need to adjust your own calculations to reflect this.
Below are some of the most important factors to consider when determining system size and potential energy production:
Technology: The higher the quality (and wattage) of the panels, the fewer modules you’ll need to install.
Shading: If trees or buildings ever cast shadows over the installation, you may need to add more PV panels than normal. And it’s probably a good idea to use microinverters instead of string inverters to ensure partial shading doesn’t negatively impact total solar system performance.
Orientation: The direction of the installation also matters, with south-facing roofs receiving more sunshine than those pointing north (assuming you’re above the equator).
Temperature: Solar panels perform best when it’s cold. This means that all other things being equal, Massachusetts has a slight advantage over a warmer state like Arizona.
The Number Of Solar Panels Depends On The House
Many installers freeze up when asked, “How many solar panels do I need for my home?” But you now have the tools to demystify the process and provide your own customers with the confidence they need to move forward with their solar installations.
If you’d like the process to become even smoother, our solar proposal software can make future consultations both easier and faster, whether you need help with feasibility studies, schematics, inspections or bids.
In addition, we provide fast, standardized solar permit drawings, professional engineering stamps, and more all within our industry leading platform.
To learn more about how you can streamline your solar design and engineering with GreenLancer, schedule a free demo with us today.