Friday, October 29, 2021

Six months of solar power

I’ve now had six full months of solar-generated power. The results? Mixed, but good, which I fully expected. I also know that the best results are likely to be over the next six months, and I always knew that, too. Overall, the results are sunny and bright.

My solar electricity system was switched on in April of this year, and I’ve been tracking the results ever since—of course I have. Over that time, I’d added more data points to my spreadsheet so that I can satisfy myself that I can see every meaningful detail of how it’s all going—every detail that I care about, anyway; I'm sure I skipped over a lot of possible data points.

Because of that obsessive spreadsheeting, I know that winter was brutal for electricity production. This makes complete sense because the hours of sunshine in Hamilton in June and July are roughly half (or less) of what they are in the summer months of December and January. That means it’s no surprise that the credit I received in June and July was less than half of what it was in May, the first full month the system was active.

What this means in practice is that I expect to get much higher credits over the summer months, even higher than in it was in May (which has about 25% less sunshine hours than January). However, this depends in large part on the weather.

Ah, weather: The other big factor in this. Overall, New Zealand had its “warmest winter—again”, though there’s always some local variations. However, it’s not temperature that affects my solar power production, it’s sunshine (obviously), and it usually rains a lot in winter in New Zealand. This past winter, Hamilton had a LOT of rainy and heavily overcast days. Logically, cloudy days, combined with fewer sunshine hours available, means lower electricity production.

The data I recorded backs that up.

The amount of electricity I got “paid” for (it’s actually credit against my power bill) was up in August and up again in September (each month’s meter reading is recorded/billed in the third week). Neither was what I’d call a dramatic increase, but it was definitely up—as were the number of sunshine hours. I thought that was hopeful.

October, however, was another level entirely: I produced and supplied 386kWh of electricity, and bought 398kWh—in other words, I supplied nearly as much electricity as I bought. For comparison, in October 2020, when I didn’t have the solar panels, I bought 676 kWh. [kWh, or kilowatt hours, is a standard measure of electricity consumed/sold].

This is the point where it’s important to note a few things. First, not all of the electricity I produce and supply to the national grid (that 386kWh in October) is power I would’ve bought if I didn’t have the solar panels, though some of it might be. Instead, it's power I wouldn't have consumed at all. The reason for that is my own practicality.

As I’ve said before, I do electricity-heavy things—like running the dishwasher, running the clothes dryer, even ironing clothes or recharging batteries—during daylight hours, ideally on sunny days. What this means is that I try to use the electricity I’m generating, which is the most cost-effective thing for me to do. That’s because the electricity company pays me less for the power I generate than I pay them for the power I buy. So, when my electricity-hungry devices consume my own solar-generated electricity, it costs me absolutely nothing to run them when the sun is shining. Even on heavily cloudy days, when I might need to buy some extra power from the grid, I still buy far less than I would without the solar panels.

The number of kilowatt hours (kWh) that I purchase from the grid, then, are a far better measure of how things are going, and there the picture is quite sunny. Looking at October again, I bought about 40% less electricity than I did in October, 2020. Even in wintry June, in 2021 I bought about 22% fewer kWh from the national power grid than I did in June 2020, and that’s despite it being the month in which I supplied the lowest amount of electricity (again, I used power that I generated, and that reduced the amount I needed to buy by that roughly 22% over the previous year, and it also reduced the amount of power I supplied). Comparing months in 2020 to months in 2021 is useful because my energy needs can be assumed to roughly equivalent, however, it’s not perfect given possible differences in the number of cloudy days, for example. Still, it’s good for getting a rough idea of how it’s going.

I have other calculations I’ll share at the one year mark, when I can compare one full year to another. However, I can say that since the solar panels when in, I’ve consistently consumed less power per month than I did in the same month in 2020. The question I can’t answer for another six months is how much the solar panels will save me over the course of a year. I can’t even reasonably do any projections or predictions because we’re not in the sunniest months of the year yet—in fact, I haven’t had the solar panels running in any of the most-sunny months. Seeing how this plays out will be very interesting—for me, anyway.

I’ll admit that when I looked at my power bills in the midst of winter, I felt disappointed, and that’s the entire reason I added more data points to my spreadsheet: I felt I wasn’t getting the whole picture, and I was right. Looking at averages, comparisons, and totals, it’s easier to see that despite the dark, dreary days of winter, overall even now I can tell the most important thing of all: For me, it was worth it on every level. I may not yet know what my annual savings will be, nor how long the system will take to “pay for itself”, but I know that I am saving money while at the same time generating clean, green electricity to help power New Zealand. Damn right I'm happy I went solar!

Update: The danger in drilling down through detailed data is that it can make us miss important things, like in this case: The thing that most people would be interested to know is, how much less am I paying now than before? Because the system's only been running for six months, and half of that was during winter, I can't yet do monthly averages that would mean anything. However, October was my best month with solar so far, and it should give some idea of what I'll likely see over summer: In September, my bill was about $154 (an amount similar to September; June and July, the coldest months, were both $25 higher). However, my October bill was for $65—meaning it was about $89 less than the month before. I expect to save even more per month over summer, weather permitting.

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