Overestimating Solar Production
One of the most fundamental determinants of the economics of solar is how much energy your system will produce. Estimates of solar energy production are related to two major factors. (We will skip a few minor factors here for simplicity.) The first factor is efficiency of the panels. This is more-or-less immutable. Ask your vendor for the efficiency rating of your panels under “Standard Test Conditions”. Other things being equal, panels with higher efficiency will produce more energy.
The second major factor is the set of assumptions about how the panels are oriented and the degree to which they are shaded. This is where an unscrupulous vendor can mislead you. How careful and conservative is he being in estimating these factors? If he models your roof as facing due south when it in fact does not, his estimate is going to suggest more production than that of someone who correctly models your roof as facing southeast, for example. Likewise, if he assumes there is no shade on your roof when, in fact, it is shaded every day after 3 p.m., his estimate will overstate electricity production. More subtly, since the amount of sun varies somewhat from year to year, is he estimating for an average year (50% of years better, 50% of years worse), or is he being more conservative (for example, 90% of years better, 10% of years worse)?
Assume you have a roof with space for 25 panels. I offer to sell you more efficient panels and estimate they will produce 10,000 kWh in the first year. A competitor offers to sell you less efficient panels but estimates they will produce 11,000 kWh in the first year. Does this make the competitor’s offer a better one?
No. Conditional on the fact that we will both orient the panels in more-or-less then same way (which is mostly determined by your roof), the more efficient panels will produce more energy. The difference in our production estimates is largely driven by differences in assumptions. Once the panels are on your roof the assumptions don’t matter — only the real world does, and that’s where the more efficient panels shine.
Don’t let someone using overly aggressive assumptions fool you into thinking an inferior system is better than it is.
Conflating Power and Product Warranties
Another way an unscrupulous vendor can mislead you is by getting you to conflate a power warranty with a product warranty.
In many cases, the warranty length the vendor will discuss with you covers only the panels, and only the power production from them. This “headline” warranty length assumes that the panels don’t fail during a shorter “product” warranty period and that other crucial parts of your system don’t fail. (We have a whole post on this.)
Certasun only sells SunPower equipment, which comes with a 25-year Complete Confidence Warranty that covers all the equipment on your roof for 25-years, period. We encourage you to read the fine print.
Two #1 Solar Companies
One of our competitors, Sunrun, claims to be the #1 residential solar company in the U.S. This is, in one sense, absolutely true. Sunrun has more customers than any other direct-to-consumer solar company nationwide. At the end of third quarter of 2018, they reported 218,000 customers.
Certasun is a much smaller company. We do business only in Illinois. However, we are a local dealer of SunPower equipment (See what makes SunPower great.) SunPower has a different business model than Sunrun and does not sell directly to consumers. They make the equipment and provide financing, but they rely on a network of local experts like Certasun to sell and install their equipment. There are currently more than 500,000 residential SunPower customers in the U.S. SunPower, therefore, is also the #1 residential solar company in the U.S. Who is #1 depends on how you count!
If you have questions about any of these items, please reach out to us via the form below or give us a call at (312) 638-0800. We’d love to hear from you.