As an owner of a solar system or when considering going solar, it’s helpful to understand what your system will output over the course of the four seasons. Here in the northeastern United States we do see significant variation in daily energy output from our systems over the course of a calendar year.
Based on real data from the Lightgauge monitoring systems we install for our customers we can closely track each system’s energy output variation during the year. If we split the year into two equal parts at the Vernal and Autumnal Equinoxes (March 21st and September 21st) we can get a quantitative handle on this variation. It turns out that, on average, 65% of our local solar system’s annual energy output is generated between March 21st and September 21st of each year. The other half of the year, between September 21st and March 21st, accounts for the other 35% of annual output.
Furthermore, if we take a look at the two month windows surrounding both the Summer and Winter Solstices (June 21st and December 21st) by comparing system outputs for June and July vs December and January we can further accentuate the seasonal variation. On average our residential solar customers see a total energy output decrease of 40-60% during the months of December and January as compared to July and August.
The factors involved in this variation are threefold.
So how does this work with your utility billing? Won’t this cause system owners to get high electricity bills all winter long when their systems are under-producing and their usage is increased due to more time in the house, higher lighting loads, etc.? Not necessarily, and this is where net metering comes into play. When we design solar systems for customers we always look at the total annual electricity usage when sizing the system. For customer’s with adequate roof space (or area for a ground mount) this allows us to design a system which overproduces enough during the spring, summer, and early fall to build up a bank of kilowatt hours with the utility which will carry the homeowner through the winter months. Thereby the effects of reduced energy production during our northeastern winters can in fact be mitigated through correct system design, sizing, and net metering (read more about net metering here).
This is also why, for our customers who get their systems interconnected in months other than March and April, we advise them to utilize their utility’s “Anniversary Date Change” process to make sure that they are optimizing the use of their net metered energy credits over the course of the year.
If you’d like to learn more about optimizing your anniversary date please call our office and speak with one of our Technical Sales Engineers.
Interested in going solar? Speak with our Austin solar panel installation experts at Lighthouse Solar to get started with a free consultation.
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