One of the most common questions that photovoltaic (PV) installers receive during early customer consultations is “how many solar panels do I need for my home (or business)?” This is a natural question, since the number of PV panels directly affects the total cost of installation – not to mention variables such as:
However, explaining technical terms such as solar insolation, voltage or kilowatt-hours to a homeowner accustomed to thinking in dollars and cents can be a challenge. If you’ve dealt with this situation before, use the following guide to make the photovoltaic installation consultation process easier and more understandable for your customers.
How many photovoltaic panels do I need to power my house?
6 kW is a good baseline and most homeowners will understand it. Nonetheless, it is important to correctly size each photovoltaic system to cover the amount of energy used by customers today and tomorrow. For example, you may want to price a rooftop solar system if the household plans to purchase an electric vehicle or install heat pumps.
To find out how many solar panels to install, read on.
How to determine the number of photovoltaic panels needed?
Here are the five most important variables to consider when determining the size of a home photovoltaic system.
1. The homeowner’s goals for solar energy and savings.
Adding just one photovoltaic panel can help generate monthly savings on electricity bills. Installing more photovoltaic modules results in higher savings on electricity bills. That’s why it’s important to consult with each customer to determine their energy and savings goals in advance.
- Do you want to have enough solar energy to meet 100% of your electricity needs?
- Do you plan to use net metering to sell excess energy to your utility provider?
- Do you need batteries to store solar energy during the day for use at night?
Clearly defining these goals is crucial before moving on to the next steps.
2. Current household energy consumption before installing solar panels.
With energy and savings goals established, you are ready to analyze the customer’s historical electricity consumption. Most homeowners focus on the dollar amount of their electricity bills, but more important are the kilowatt-hours they have used over the past year.
The higher the electricity consumption, the more solar panels will need to be installed to cover that energy consumption.
3. The power needed to power typical appliances.
The next step is to develop a clearer picture of the customer’s energy needs in the future. The historical analysis already takes into account any energy-intensive appliances that are already in the home. However, with the growing number of families and more electronic gadgets, energy needs are likely to increase over time.
In fact, “electrification” of the home is very common among solar customers, regardless of whether they replace it:
- Gas-guzzling cars to electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs)
- Natural gas or propane furnaces for electric alternatives such as heat pumps
- Gas water heaters for electric or hybrid water heaters
The goal is to power more appliances with free solar energy instead of electricity generated from fossil fuels. When talking with customers to determine how many solar panels they need, it’s a good idea to show them charts and infographics so they can better understand the impact of future purchases on their production and energy needs.
In addition, many customers can also make energy efficiency improvements to their homes. For example, replacing incandescent light bulbs with LEDs helps reduce electricity consumption. This allows you to install a slightly smaller solar panel system to meet the homeowner’s energy needs.
4. How many hours of sunlight reach a given area?
Geography can have a huge impact on the performance of photovoltaic panels, with a state like Arizona receiving more direct sunlight than a place like Massachusetts. The same goes for the changing seasons, so it makes sense to have electricity bills for the entire year, not just for the last few months.
Fortunately, the National Renewable Energy Laboratory (NREL) publishes several resources on solar radiation to help you determine the average amount of sunlight for each geographic region throughout the year. These charts can make your own volume estimates much more accurate.
However, there remains one piece of the puzzle.
5. Factors affecting the performance of solar panels.
Photovoltaic panels are tested under ideal laboratory conditions. However, the average home is in the real world, where constant exposure to UV radiation is impossible. Therefore, calculations must be adjusted to determine how many solar panels a home needs to reflect this.
Here are some of the most important factors to consider when determining system size and potential energy production:
- Technology: The higher the quality (and power) of the panels, the fewer modules you will need to install.
- Shading: If trees or buildings cast shade on the installation, you may need to add more photovoltaic panels than usual. It’s also a good idea to use microinverters instead of daisy-chain inverters to ensure that partial shading doesn’t adversely affect the performance of the entire photovoltaic system.
- Orientation: The direction of the installation also matters, with south-facing roofs receiving more sun than north-facing ones (assuming you are above equator).
- Temperature: Solar panels work best when it’s cold.
How many photovoltaic panels will I need?
The average home in the United States typically requires between 17 and 25 photovoltaic panels to fully power it. However, the exact number of solar panels needed can vary depending on several factors, such as the average household’s electricity consumption, the available roof area for photovoltaic panels, geographic location and solar panel output.
Solar panels are usually measured in watts, and most generate between 250 and 500 watts of power. To determine the number of solar panels needed for a particular home, calculate your total household energy consumption and divide it by the average output of the solar panels you are considering. Please note that this calculation may also take into account factors such as shading, orientation and efficiency losses.
Will I need more solar panels on a shaded roof?
A shaded roof can actually affect the performance and efficiency of solar panels. Shading reduces the overall energy efficiency of a solar panel system because shaded panels receive less sunlight and generate less electricity. However, the effect of shading on a solar panel system can vary depending on several factors, such as the type of shading, the type of panel and the design of the system.
In some cases, it may be necessary to install additional solar panels to compensate for the reduced solar power generation caused by shading. The exact number of additional panels will depend on the degree and duration of shading and the home’s overall energy needs.
Do I need fewer solar panels if I use higher wattage modules?
Using higher-powered modules could potentially allow you to install fewer solar panels to meet your home’s energy needs. Because higher-powered solar panels produce more energy per unit, a system consisting of higher-powered modules may require less total panel area to generate the desired amount of electricity. This can be particularly beneficial in situations where space is limited, such as on residential rooftops or in densely populated areas. Higher-powered solar panels, however, are sometimes larger in size, requiring more space on the roof.
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“How many solar panels I need” depends on the house.
Many installers freeze in immobility at the question, “How many solar panels do I need for my house?” But now you have the tools to explain the process and give your customers the confidence they need to proceed with solar panel installation.
If you want to make the process even smoother, our solar services for installers can make future consultations easier and faster, whether you need help preparing permit-ready plan sets, interconnection applications, or solar engineering reviews through our industry-leading platform.