To continue the five year review of our solar array, our annual electricity bills reliably follow the trends outlined in the previous post, with the exception of the solar year 2024. To explain this outlier, we need to take a look at how deficits and surpluses as well as fixed costs affect the billing.
This analysis is mostly relevant to ComEd customers in northeastern Illinois with a net-metering agreement. Customers with other electrical suppliers and in other service territories are likely subject to different tariffs, charges, and agreements.
We find three billing categories on our ComEd bills:
- Supply costs are the cost for the electricity (kWh) we pulled from the grid (supplied by ComEd). If our solar production per given month is larger than our electrical consumption, this zeros out.
- Delivery costs are also often referred to as fixed costs. These are the costs for having an electrical meter and a connection to the grid (grid tied system).
- Taxes & fees are a percentage applied to the electricity (kWh) we pulled from the grid (supplied by ComEd). If our solar production per given month is larger than our electrical consumption, this zeros out.
The chart above shows the cost per solar year for each of the three billing categories, plus the total annual cost, since we activated our solar array on December 24, 2019.
For the three apartments in our 4,500 sf building, our annual electrical cost started at a “whopping” $403.71 for solar year 2020. Not that surprising, considering that this was also the solar year where we ran the biggest deficit.
Equally unsurprising is that our lowest annual cost was $141.44 during Solar year 2023 with the 995 kWh surplus. Because of that surplus, we incurred no supply cost and taxes & fees. What stands out is that our annual cost rose to $170.55 in 2024, despite the 715 kWh surplus.
That increase is due to the rise in the delivery cost (fixed fees) during solar year 2024 by a total of $29.10. And as long as we have an electric meter and a connection to the grid, we will be subject to the delivery cost.
And what happened to our surplus? Think of it as a charitable donation. With our net metering agreement, at the end of every solar year, our account is reset. If we run a deficit, we need to pay up for the electricity we pulled from the grid. If we run a surplus, it will be erased and we start at zero for the next solar year.
With solar vs. without solar
We just established the bill total for the whole building per solar year with our solar array. But what would we have paid if we did not have the solar array on our roof? Well, there is a spreadsheet for that.
Broadly speaking, we would have paid around $1,500 for electricity per solar year for the three apartments in our 4,500 sf building. That translates into roughly $1,200 to $1,300 in savings per solar year.
These are real “feel good numbers”, which are in line with the savings prediction we got from Lisa Albrecht at All Bright Solar (our solar installer), during our consultations with her when we went down the solar road.