Seasonality of Renewable Energy Production

As the weather improves, and it’s possible to work safely on roofs in northern climates, we know that 90% of all solar power system installations occur between May and October. April and November account for most of the other 10%. In the remaining months, everyone tends to plan and design their systems, so that they can hit the ground running in the spring. Knowing how seasonal our industry is for installation, made us want to look into the seasonality of renewable energy production – and it isn’t as clear-cut as you may think. First off, “renewable energy” covers a lot of ground, so let’s make clear that we aren’t considering hydro-electric. We can also discount the relatively small geo-thermal market – not only because it accounts for so little production, but because it’s not seasonal to any degree at all. So that leaves us with wind and solar.

Solar energy production, as you might expect, increases between the spring and fall equinox. The days are longer in the northern hemisphere, and because it’s so much warmer we naturally expect energy production to be higher. And it is… but it’s not as unbalanced as you might think. Throughout Canada and the northern US, it’s close to a 60-40 mix. The peak daylight hours occur at the summer solstice, when southern. Ontario gets about 15:26 of daylight. Over the six months between spring and fall, the average is 13:05. The 6 month average between fall and spring at 10.50. That’s a 42% difference in hours of sunlight – which matches closely. The other variables such as snow cover, height of the sun, etc, barely seem to enter into the equation.

Wind power production is also highly seasonal, but not on the same lines. In Canada and the US, wind power production is at its peak in March & April, and it’s lowest in July/August. Both equinoxes are fairly high, with the low points at the solstices. This is almost entirely due to changing weather patterns and storms. Wind power production in March is 2.5 times what it is in the summer.
Energy consumption in North America more closely parallels solar production – with peak use during June/July/August. Clearly we love our air conditioning. This close match to the solar production cycle has caused the US and German governments to call for an increase on solar reliance in the past year. Clearly, where grid-tied solar can offset peak consumption with peak production, it’s a great solution.

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