Are Online Solar Calculators Accurate?
This is probably not the answer people want to hear.
It would be nice to simply plug your address and electricity usage into one of the many websites that offer a "solar calculator" that is supposed to analyze your home and produce a report that explains what you need in terms of a solar system; and while most of these sites are well disguised traps to collect your info so they can sell it to multiple others, that’s for another article. So, are these online solar calculators accurate?
Well, the short answer is probably not.
Before diving into all the necessary factors these calculators are most likely not taking into account, I will explain what they are actually doing. Generally it starts by the owner inputting their annual kWh usage which seems simple enough but you may be surprised how many people actually self report inaccurately to begin with. From there, the website has a 3rd party plug in that analyzes sun hours and overall sun exposure a roof will get. From there, it’ll estimate a system size that should produce pretty close to what you use on a yearly basis without much other information, generally leaving the homeowner with too much confidence that what they recommended is simply what they need. Even worse is when it starts recommending battery needs as well.
If a solar calculator like the one in the picture asks about square footage, it's not real. What I mean by that is, square footage at best can only be thought of as an introductory question. It's not the size of the house that determines electrical needs.
Analyzing your solar needs is far more complex than what a generic solar calculator can tell you. Let’s go over more information that somebody needs to know, or the calculator would need to factor in theoretically, in order to give you a proposal that’s actually built for you specifically:
1. The calculator would need to have your utility’s net metering schedules built-in. The reason I know that these online calculators are not taking this into account is because even the top software’s that cost hundreds of dollars a month to use struggle to keep up with the ever-changing rate schedules along with buyback rates utility companies credit you when you send power back to the grid whenever the home cannot use what is being produced. The reason this is SO IMPORTANT is because in California, for example, if you install a solar only system that cover 100% electricity offset but the proper battery storage is not included, only 40-50% of you actual bill will be gone even though you have 100% solar offset. In many parts of the country the net metering is “pretty good” but not a 1 to 1 buyback and so if your utility offers you a buyback that is somewhere in the 50-75% value range, the calculator needs to know that specifically. I cannot express enough not only how every utility has written their own complex net metering rules, but keeping track and updating thousands of these is not being done by a solar calculator lead funnel.
2. The calculator is not asking what your future needs and goals are. What if somebody is prepping to convert their gas stove, water heater, heater, to electric, buy an EV, buy a jacuzzi, etc? Is the calculator asking how many miles you drive?
3. Do you need solar only, solar with battery but without backup capabilities, solar with battery partial or full home backup, everything and a “smart panel” like a SPAN panel upgrade? Most people go into solar thinking they need battery with backup but most don’t necessarily end up buying that once they understand how it all works. The problem is presenting offers for someone to buy something they may or may not be able to alter later without explaining all the options and capabilities.
4. Is the sun hour estimate even accurate? There are tons of software options that professional solar consultants use and pay for to analyze roofs and solar production. Just like with anything else, there is a variation of quality and two different softwares with the exact same system built will be providing two different production figures. Knowing the variation of results even amongst the paid softwares, I don’t see how a free one can be thought of as reliable.
5. Did the calculator explain the equipment options? Like I mentioned in the beginning of this article, these solar calculator websites are usually just lead generator sites which means they are there to attract you and tempt you into inputting your information so they can sell it to a multitude of different contractors that will then contact you and try and sell you a system. Of course this is how business works and there is nothing wrong with the system on the surface. The problem is that going solar is more complex than the average person realizes and when you’re spending somewhere in the range $20k-100k you really want to make sure are investing properly.
Julian Todd-Borden
Owner of Superior Solar Consulting
D. (760) 473-5878
