Solar system design: How does it work?

The process of how solar installers design a solar energy system is often a mystery for most consumers. Because of this, we would like to give you some insight into how solar installers design a solar power system for your home or business. Solar system design takes into account two important factors – the amount of space that you have available for installing solar panels and the amount of electricity you consume annually. Other factors, like shading analysis and the efficiency of solar panels and inverters, also come into play, depending on your property.

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Here are the three main steps to proper solar system design:

  1. Calculate daily energy use by determining watt-hour use per month/year (this information will be on a given utility bill)

  2. Get a system size estimate and figure out how many solar panels you need

  3. Shop for the right solar system based on the efficiency and output of the panels you choose to effectively design your perfect system!

Assuming that you are interested in installing solar panels on the roof, the amount of viable roof space determines the maximum number of solar panels that can be installed. An individual solar panel varies in size but is usually around 16 square feet in rectangular shape. The panels are affixed to racking systems that are more efficiently designed when installed in a contiguous space together rather than spread out all over the roof. The available roof space - limited by vents, chimneys, dormers, and any required offsets from roof edges or roof-mounted equipment – may limit the system size such that a solar system offsets less than 100% of your annual electricity consumption. The average solar system in the US consumes about 300-400 square feet of space, so your viable roof space may limit the size of the solar system you are able to install. In this case, installers may recommend higher-efficiency panels that generate more electricity per square foot than standard panels. These will also come at a higher cost, but this is something you might consider depending on your personal goals.

An average solar panel system may generate different amounts of electricity based on your location in the world and the orientation of your roof, so installers will use various tools to estimate the viable solar system size. These tools allow installers to use aerial imagery and to "draw" in system designs on your roof space in order to estimate the size of a system that will fit and how much electricity this system will produce each year, given a number of assumptions. If you'd like to try this yourself, you can go to PV Watts, a tool developed by the National Renewable Energy Laboratories, to estimate your system size and annual production.

One of the first pieces of information a solar installer might ask for is twelve months of electricity bills. While this might seem like a lot of information right off the bat, this gives the installer a sense of how much energy you use throughout the year. Often an electric bill will include the last twelve months of usage history in a table or a chart, removing the need to fish around for past bills. Armed with your electricity usage information, the installer can determine how big of a solar photovoltaic system would be required to offset 100% of your annual usage. This will vary by your location and roof profile.

Typically, solar panel systems are designed to cover 100% or less of annual usage to maximize the financial benefits, but if you are planning to increase your energy use in the near future – for example, if you are planning to buy an electric car or converting from oil to electric heat pumps – you might consult with your solar consultant to estimate your expected energy demand in order to design a system that better matches that use profile.

If your roof has shading – from neighboring trees, other buildings, or large chimneys – installers may choose to leave these areas uncovered by solar panels to optimize the production of the system or may place panels in these locations with the understanding that these panels may produce less energy at certain times of the day. Installers may also suggest changes to system design to create separate solar panel strings that are designed to avoid power loss from shading or may suggest the use of micro-inverters or power optimizers to help mitigate the impact of shading of the production of the overall system. The latter two technologies may come at a higher cost, but these costs may be justified by the additional power they help your system generate.

The above factors are taken into account when designing a solar system for your home or business. The process of providing an initial system design can be quite quick and can often be turned around within a day or so. Other factors – such as the structural integrity of your roof, the condition of your existing electrical system, or the specific impact of shading – may require that solar installers visit your property to gather additional information in order to develop a system design and a price quote that they can stand by. To get started, check out some helpful tips we offer to all new solar shoppers:

Three Tips for Solar Shoppers

1. Homeowners who get multiple quotes save 10% or more

As with any big ticket purchase, shopping for a solar panel installation takes a lot of research and consideration, including a thorough review of the companies in your area. A recent report by the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) recommended that consumers compare as many solar options as possible to avoid paying inflated prices offered by the large installers in the solar industry.

To find the smaller contractors that typically offer lower prices, you'll need to use an installer network like EnergySage. You can receive free quotes from vetted installers local to you when you register your property on our Solar Marketplace – homeowners who get three or more quotes can expect to save $5,000 to $10,000 on their solar panel installation.

2. The biggest installers typically don't offer the best price

The bigger isn't always better mantra is one of the main reasons we strongly encourage homeowners to consider all of their solar options, not just the brands large enough to pay for the most advertising. A recent report by the U.S. government found that large installers are $2,000 to $5,000 more expensive than small solar companies. If you have offers from some of the big installers in solar, make sure you compare those bids with quotes from local installers to ensure you don't overpay for solar.

3. Comparing all your equipment options is just as important

National-scale installers don't just offer higher prices – they also tend to have fewer solar equipment options, which can have a significant impact on your system's electricity production. By collecting a diverse array of solar bids, you can compare costs and savings based on the different equipment packages available to you.

There are multiple variables to consider when seeking out the best solar panels on the market. While certain panels will have higher efficiency ratings than others, investing in top-of-the-line solar equipment doesn't always result in higher savings. The only way to find the "sweet spot" for your property is to evaluate quotes with varying equipment and financing offers.

For any homeowner in the early stage of shopping for solar that would just like a ballpark estimate for an installation, try our Solar Calculator, that offers upfront cost and long-term savings estimates based on your location and roof type. For those looking to get quotes from local contractors today, check out our quote comparison platform.

Find out what solar panels cost in your area in 2024
Please enter a five-digit zip code.
  • 100% free to use, 100% online
  • Access the lowest prices from installers near you
  • Unbiased Energy Advisors ready to help
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