2023 Solar System Performance
May through August; we have some more work to do
As I write it is the first day of Fall, on the 21st I moved the solar panels back to 40° from horizontal; the next move will be on or about December 21st, with the panels going closer to vertical to better capture the low winter sun. Below are the settings in degrees from horizontal that we are using for our latitude and season:
Spring Mar 21 set to 40 deg
Summer Jun 21 set to 15 deg
Fall Sep 21 set to 40 deg
Winter Dec 21 set to 68 deg
The Solar System 2023 to Date
Let's have a look back at the performance of the solar system, as installed and configured. Our first complete month after completion of the installation was May, and in our bill for May we paid zero for energy. That's a win obviously. May is good because we had virtually no need for heating or cooling. Look in particular at the orange bars, "Import;" that is the energy we took from the grid to satisfy loads, charge the batteries, or both.
Now looking at August, we see a lot more orange on the chart, although on some days it is near zero, and on other days very, very high; of course the high days involve running the AC. AC is a total energy hog, total. Fortunately in a long-term "grid down" scenario we don't need AC; it's nice don't get me wrong, but we don't absolutely need it.
As you can see clearly from this August energy usage detail, temperature drives our energy use very significantly. This data is from our grid power provider, and as you can see on some days, Aug 8, 16 and 18 in particular, we used almost no grid power, solar provided for all or most of our need. But on other days, especially the 24th where the high was in the mid-90’s and the average in the mid-80’s, that’s really hot hereabouts, we pulled a lot of energy from the grid. In our case temperature matters.
It is not all bad news though. In the table above, again from our grid power provider, we are looking at a comparison of our electric bills for the August 2022 and August 2023 billing cycles; this is informative.
First things first, temperatures; some high and low differences clearly, but the average is basically the same, just 1 degree separates 2023 from 2022, 2023 being a degree cooler, on average. For the purposes of this analysis I’m calling that average temperature difference insignificant in the scheme of things.
In dollar terms our usage charges went down by $86.91, which is a 65.5% reduction from 2022. That’s good, but not good enough, to return our investment in 10 years.
Again in dollar terms, our total charges went down by $101.13, a 54.5% reduction.
The reason the reduction in total charges is less percentage-wise than the reduction in usage charges is because there are costs on the bill unrelated to energy usage, and the only way to make them go away is to disconnect from grid entirely.
Looking again at our August 2023 detail, we can see that ($45.00 + $3.63 + $0.88 - $10.72) / $84.54 = 0.459, or 45.9% of the bill, has nothing to do with usage. In fact, of the $84.54 total for August, only 30.2% of the total was for the energy itself.
We can do better I’m sure, on a couple of different fronts, but I have to say that with a scheme where only 54% of the cost to us of the energy, is the energy itself and its distribution, we are definitely starting out behind the power curve, pun intended.
What Can Be Done?
Let me start with what cannot or will not be done. The image above is from just a few days ago, with the array set at its summer angle of 15° from horizontal; but that’s not the point. See how the array is tucked up against the tree-line to its east? That was a decision we made to preserve our view to the lake due north of the house; we moved the array to the east out of our direct line of sight. I am not saying that was a bad decision, but as the old saying goes, decisions have consequences. Those trees to the east…that tree-line runs roughly north-south, those trees are a hundred feet tall more or less, and when fully leafed out by mid April lets say, very little direct sunlight hits the panels until late morning, and the panels are not seeing full direct sunlight until shortly after noon. I could sharpen my pencil, but I reckon we are losing 25-30% of the solar energy year-round, and probably closer to 40% in summer. Just sayin’. And we are not moving the panels regardless, because they are now anchored in 6 tons of concrete. Furthermore, we are not taking the trees down.
What we can do however falls into three categories:
Forego the AC, hang laundry for drying exclusively, etc. Simple, yes. Probably not happening so long as the grid is available.
Install more batteries, and/or
enter into a “net metering agreement” with the utility.
Net metering is a billing mechanism that allows residential and commercial customers who generate their own electricity from solar power to sell the electricity they aren't using back into the grid.0 Under a net metering agreement, the grid acts as energy storage for the solar homeowner, banking the power they generate so they can use it later. The utility tracks the meter to record the net energy usage (energy consumed minus energy sent to the grid) so they can bill or credit your account based on overall usage. Grid-tie solar system owners receive credit for sending electricity into the public utility grid and use those credits to offset their energy bill.1
0 seia.org
We will probably do both 2 and 3; entering into a net metering agreement soon (it’s at no cost to us), and adding batteries before next spring; both are forms of additional storage.
I made a decision early on not to enter into a net metering agreement with the utility, and to not configure our system to put excess power on the grid, until we better understood where we were with respect to electrical self-reliance. As a result, when solar energy is available in excess of our load and battery charging needs, the system essentially throttles, or limits power production from the panels; simply stated, there is no place to put the power because we have fully charged the batteries and I have told the system not to “bank” excess power on the grid.
Summary
I am satisfied with the performance of the system. We can do better in our behavior, we can reconfigure the system to bank power on the grid, and we can add storage batteries to improve our return on investment (ROI). But, given the decisions we have made, I think the system is performing as designed.