When we talk of going solar, most people consider this to be a complete replacement of grid electrical power with the power generated by your solar panels. It’s not always possible to generate enough solar power to completely power a home. There are a few reasons for this:
In Example 1, we see a customer with gas heat, leaving electrical generation needs in the Winter months fairly low. There is a marked spike in usage through the hot months, where usage is near double that of the rest of the year.
In a case like Example 1, we design the system to cover all usage except the 4 months that are at least 40% higher than the other months. In this case, it doesn’t pay for the homeowner to purchase enough panels to cover the high usage months because up to half of the energy they generate in the other 8 months of the year is sold back at a discount or thrown away.
For this customer, I designed a system that covers all the non-summer months and will cover up to about 80% of the summer months. Since offset is calculated on an annual basis, we are still able to get this homeowner to the 100% Offset rating.
In Example 2, we see a relatively consistent usage pattern with one month that is considerably higher than the rest. In this case, the anomaly month is disregarded because it was caused by the Winter storm of Feb. 2021, which was not a common event. For purposes of calculating usage, these types of months should be flattened a bit to give a more realistic usage figure.