A commercial solar array can achieve a payback period of less than six years in building with abundant sunshine and high electric tariffs. According to the Consumer Price Index Report published in June 2022, US electricity prices were up by 13.7% in the 12-month period between June 2021 and 2022. However, this also means greater savings for solar array owners: a system saving $10,000/month with the kilowatt-hour prices from one year ago would now be saving over $13,000/month.
The financial return offered by a commercial solar installation depends on multiple factors: roof space available, sunshine conditions, local kWh prices, sizing the system properly, using quality equipment, and getting a professional installation. Local incentive programs and regulations must also be considered, and these vary by state and city.
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In this article, we will discuss three important features you should look for when comparing solar panels for commercial buildings.
1) Check the Solar Manufacturer’s Background and Warranty
Most solar panels look similar, but this also means high-quality and low-quality modules cannot always be identified at a glance. To make sure you’re getting a good product, you should do a background check of the manufacturer and review their warranty conditions carefully.
- A long warranty with the backing of an established brand ensures that you get a financial return after going solar, since defects and malfunctions are covered.
- On the other hand, if you choose a solar brand with a questionable track record, your panels may fail in a few years (or months). Then when you try to contact customer support, you may find that the manufacturer went out of business!
Solar panels normally have two types of warranties, and understanding the difference between them is important. The product warranty covers you against defects and workmanship issues, while the power production warranty applies if solar panels lose their generation capacity faster than manufacturer specifies. Typical product warranties range from 10 to 25 years depending on the manufacturer and solar panel model, while power output warranties range from 25 to 30 years.
For example, the product warranty would apply if any of your solar panels fail suddenly within the coverage period. On the other hand, the power production warranty would apply if your solar panels are rated for 93% of initial output after 10 years, but they have degraded to 90% output in just five years of use.
2) Look for Large High-Wattage Solar Modules
If you use solar panels with a high rated wattage, you will need less to reach a given system capacity. This can help you save on installation costs, since there are less modules in total and the amount of racking needed is also reduced. Commercial solar panels had a typical wattage between 300 W and 400 W a few years ago, but several brands now offer modules rated at 500 W or above.
As a quick example, assume the optimal solar array size is 500 kW in a commercial building. If you choose the newer 500-watt modules, your contractor will only need to install 1,000. To reach the same capacity with smaller modules rated at 360 W, the contractor must install almost 1,400. This will most likely increase your project costs: the installation becomes more complex because there are 400 additional modules, and you need more racking to hold them in place.
This does not mean that lower wattage solar panels are inferior products; they have their own applications. Residential solar systems tend to use smaller panels, since they are easier to handle on sloped roofs, and they can be used in spaces where large modules don’t fit easily.
3) Look for Solar Panels with a Low Temperature Coefficient
We tend to look at wattage values when comparing solar panels, but the temperature coefficient is also important. In simple terms, the temperature coefficient tells you the performance loss when a solar panel heats up, using 25°C as a reference value.
- A temperature coefficient of -0.40% per °C indicates that the module will lose 4% productivity with a 10°C rise, and 8% productivity with a 20°C rise.
- On the other hand, a module with a coefficient of -0.30% per °C will only lose 3% and 6% productivity when exposed to the same temperature rise.
Keep in mind that the performance loss due to temperature rise is a temporary effect, not permanent damage. However, consider that solar panels operate directly under the sun for long hours, and they tend to heat up. With a low temperature coefficient, the productivity loss due to temperature is mitigated.