Thursday, September 19, 2019

Solar System Update


I got my FPL bill today.  It's for $31.66.  My September bill last year was $119.14.  It appears that I saved about $88 this month.  I had solar power during the day every day this month, and I did not have solar power last year.

This is somewhat unreliable, because bills on corresponding months from one year to the next are never the same anyway.  My bill last month, which included one week of solar power during the day, was $98.05.  The corresponding month last year, the bill was $134.68.  The July 18 bill this year was $107.40, and the July bill last year was $149.10.  This year's June bill was $122.36, and last year's was $131.81.  So I was already using less electric power monthly this year than last, and I don't know the reason.  I don't think I did anything different this year, although it looks like I must have.  One difference is a new central AC unit I got, which was in July last year.  It's possible that it resulted in a decrease in my electric power usage, if it was much more efficient.  I usually turn on my central AC in about May.  This past May, my bill was $85.20.  The May bill from last year was $111.72.  So, I saved myself about $26 without the solar panels.  My June savings was about $9.  The July savings was about $42.  It's hard to make sense of savings, except to say my current bill, in a very hot month, is really low compared to last year's bill for the same month.

So, the question is, about how much are these solar panels worth to me on an average monthly basis.  For the moment, I have one month to use as an example-- imperfect as that example is-- and the suggestion is that it could be around $88.  I said before that after I get my tax credit, the panels will have cost me about $13K.  If I saved an average of $88 every month, it would take me about 148 months to get back the money I spent for the panels.  That's almost 13 years.  The warranty for almost all of the components of the system is 10-12 years, with one component warranted for 25 years.  The expected degradation of performance is about 0.6% per year.  So, by the end of the 13 years it will take for me to get my money back, the panels will be about 8-9% less efficient.  It might, then, take me more like 14 years to get my money back, unless the panels stop working after the warranty period.

In the meantime, I get the intangible benefit of knowing I'm using less of the non-renewable sources of electric power.  That would please some people to know, and other people wouldn't care.  In my case, it pleases me to know it.

There are two other things worth mentioning about solar panels at my house.  One has to do with my car.  It's purely electric, and when I plug it in, it uses much more electricity than does everything else in the house.  On days I plug it in, which I do during the day, it uses all the solar power I make, and significantly more.  This usage lasts for about 4-5 hours, until the car's batteries are full, at which time it doesn't draw electric power any more.  If not for my car, my electric bill this month would be about $10.  It's a tricky business to know when to plug in the car.  If I plug it in during the day, I'm using (free) solar power as part of the electric source.  This is good.  But electric power I buy from FPL is more expensive during the day than it is at night, so the power I'm buying during the day, which is only part of what I need to replenish the batteries, costs more per kWh than electric power I would buy from FPL at night, of which I would need to buy more, because I don't get the solar boost at night.  I haven't figured out how to calculate which is a better deal.  I'm working on it.

The second feature of solar power is that if the power goes out during the day, I still have power, at least for about 7-8 hours.  And it's enough to run everything in the house, except powering the car.  I can run the AC, the refrigerator, lights, the computer, whatever I need to run in the kitchen, and do laundry.  But only during the day.  I have no power at all from late afternoon to about 10:00 AM when the power is out.

That's my solar system update.  I still say solar panels on Village buildings would be a great idea, if we weren't diverting so much money to the attorney.


6 comments:

  1. Cool Fred! The way fpl calculates is bill is based off a weird number of days they choose to bill you. Some months 29 days, some months 33 days. I do not understand why they do this, but they do. Now if you want a glimpse into the way my mind figures out stuff, try to follow along. =D

    You can always look at the kilowatt-hours used in the month. Then divide that total number by the days they chose to bill and you get an average per day kilowatt-hours I think the abbreviation is kwh. Now if your solar panel system is rated for 13000 watts, that is 13 kilowatt rating and then multiply that by the average number of hours you are producing and you get the amount of kwh your system is producing.

    Now you can subtract your average daily kwh- the production kwh. And the number you derive multiplied by I think 10.9 cents gives you the money you will have to pay + base service rate, taxes, and whatever they throw on there.

    Lastly, if your kwh produced is more than your average consumption ex. The above derived number is negative, then this would be your system is oversized and you would be feeding the grid more than you use, so that inturn equates to you giving money to fpl.

    Hope whomever just read this understood. ��. If not you can always Google a calculator. Or contact me. I have built a spread sheet to calculate what size solar system you would need to run your house.

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    1. Thanks, Jared. That's one variable. I'll check in with you about it.

      The other variable, which I haven't even tried to figure out yet, is the price difference between electricity bought at peak hours, and that bought at off peak hours.

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    2. Jared, I want to come back to the unpredictably moving target that is the electric bill. You're certainly right that if corresponding months don't have the same number of days in them, then it's hard to compare. Also, because for everyone except me, the biggest drag on the electric bill is air conditioning, it matters what was the daily temperature in a given month. This is very variable.

      So, if you look at my bill for two consecutive Junes, let's say, you'll see that the bill for the June when I didn't have the new AC was only $9 more than for the next June, when I did have the new AC. Was the number of days the same? Maybe not. Was the temperature the same? Maybe not. And of course, was the FPL rate the same for those two years? Maybe not.

      So, it's really hard to make reliable sense of this. Except to say that nothing in the world except my decision to stop using electric power, or, as is the reality, the presence of solar panels, will lead me to have a bill of $32 in August/September. Did those panels save me $88? Who knows? But they saved me something, and it was a lot. It could have been $88, or it could have been more than that, or it could have been less than that. It's essentially impossible to tell.

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  2. Regardless, you are doing a good thing for the earth, Fred, and that's worth a lot to all of us. Multiply "Fred" times "world population" and the net net would save this orb for future generations. The logic is just too clear, but clearly not clear enough for world leaders, or at least our current blob in the White House. I agree that BP should install solar panels to power all (four?) public buildings: PW, log cabin, rec center, village hall. Being responsible and green should be part of our "vision." We are small and nimble enough to pull that off if we didn't have our own blob in power.

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    1. I agree. The problem structures are PW and the log cabin. They're too shaded to sport panels themselves, but other panels (Recreation building, Administration building) could certainly be used to supply power to the other two.

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    2. Agree with you both that that the village should take the plunge. It's not a big $ savings, but it certainly does speak volumes for our image and how we want to treat future generations. And at the recreation center, we can use it as a teaching tool for the little ones.

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