This installation tip was provided by Dan Glaser, sales engineer, Panasonic

The simplest and most common metric used to evaluate solar modules has been their cost per watt. But as the solar industry matures, we understand there are more important factors that affect long-term performance and the ROI of a PV solar system.

Module efficiency

Efficiency is a direct measure of how much energy you can obtain from a given area or how many kilowatt-hours you can extract from a roof. There are many ways to increase wattage of a module, including increasing its physical size. But the only way to increase module efficiency is through R&D investments at the cell and materials level.

With roof constraints often a barrier to meeting increasing energy demand from homeowners, efficiency should play a key role in maximizing useable roof space. Higher efficiency panels deliver more kilowatt-hours to the customer, with a greater ROI.

An added benefit to installers: using modules with higher efficiency and performance can result in fewer modules needed overall, reducing labor and BOS costs.

Temperature coefficient

The nameplate power rating of a PV module is taken at 77° F, and power starts to decrease as cell temperatures rise above 77° F. The amount of power lost above 77° F is directly correlated with a module’s temperature coefficient.

The lower the temperature coefficient number, the better that module will perform as temperatures increase. This is important in all regions, not just hot climates. When the sun is shining, rooftop temperatures can easily exceed 77° F even with ambient temperatures below 50° F.

You can compare the temperature coefficient of various panels by their respective data sheets. However, to fully realize the extra kilowatt-hours (and higher ROI) achieved from a better temperature coefficient, advanced software platforms should be used for a detailed analysis.

Warranty

Quantifying the value of a solar panel’s warranty is sometimes difficult. The company standing behind a long-term warranty should be the first point of scrutiny. Just because a company offers a 25-year warranty doesn’t guarantee it will be around to honor it. For a minimum 25-year investment, installers and homeowners should choose a manufacturer that is financially healthy, stable and brings a longstanding reputation for product quality and customer service.

The warranty performance guarantee is also important. The difference in power production between an 80% and a 90% performance guarantee, stretched over 25 years, can add up to thousands of dollars of electricity generation. This will have a significant impact on project ROI and can be the difference between a smart and disappointing investment.

Panasonic high-efficiency HIT solar modules provide one of the world’s lowest temperature coefficients and degradation rates, backed by a complete 25-year warranty.