Suburban 5-4-and-a-Door Solar: Summer Bill Summary

We have now had solar panels on our house for the three traditionally hottest and most power-hungry months of the year in the Atlanta area. While one year is not a trend, we thought it would be insightful to compare the bills from these three months to previous years.

From 2013 to 2016, the collective bills for the months of July, August, and September (added together) averaged $948. This year, we paid $572 for those three months. That's a savings of $376 over that three month period.

In terms of kWh, the average power used in the months of July, August, and September from 2013 to 2016 was 6121kWh. In 2017, we used 4012kWh - a savings of 2109kWh over that three month period.

What is particularly interesting is to see the effect on the yearly spending running graph. This is a graph of the total spending for the previous year - the same graph that was used in the previous post on ROI calculations. That big drop off at the end is the effect of saving over $350 in three months. We hope that the trend will continue as we enter the cooler part of the year.

There are obviously a lot of details involved, but this is still a striking change. Some of the savings was certainly due to conservation and the 2-day power loss from the hurricane. For those who want to see more number details, click here. For more on our solar story, follow the solar tag below.

The 21-Word Review: The King and I (Fox Theater)

I don't normally write reviews of live theater, but Robert said he was looking forward to my review of this show.

The 21-Word Review: Forged by Bart D. Ehrman

Does it matter who wrote the Bible? Can we really know for sure? Does the author have an axe to grind?

The 21-Word Review: Ready Player One by Ernest Cline

A science fiction novel based on eighties popular culture? How have I never read this before? It was written for me.

The 21-Word Review: The Mummy (Delta In Flight)

My daughter declared this the worst movie she's seen in her life. I've seen worst, but not with this expensive cast.

The 21-Word Review: Hidden Figures (Amazon On Demand)

It deserved the awards. Even if it's fictionalized a bit, it's still an amazing story of real people. Watch it. Now.

The 21-Word Review: The Saint (Netflix On Demand)

A movie / failed pilot restart of an old series. I am a fan of Eliza, but the writing stunk worse than ....

The 21-Word Review: Kong: Skull Island (Amazon On Demand)

One of the better Kong adaptations throughout a long history of usually pretty bad Kong adaptations. And thankfully no Faye Wray.

The 21-Word Review: In the Kingdom of Ice: The Grand and Terrible Polar Voyage of the USS Jeannette by Hampton Sides

Usually when I read a book I try to imagine myself in the scene. That did not apply here. Not once.

I hate political blog posts. Then again ...

When I was an undergrad, I went to the UK with some Georgia Tech History and English professors for the summer. This was before Tech had much of an overseas program, and it was a small, close-knit group of us. This was the summer that the state of Georgia was debating whether or not the Confederate battle flag should be removed from the Georgia state flag.

As a relative newcomer to Georgia, I didn't know a lot of Georgia history. Over breakfast one morning I mentioned that I thought it was silly to change a symbol that had always been on the flag just because it now meant something different to some people.

The Tech History professor who was traveling with us (Gus Gieblehouse - probably spelled differently) proceeded to give all of us a calm, reasoned, and well informed history of the Georgia state flag - including the fact that the Confederate battle flag was added as a defiant gesture against a federal government that insisted on integration.

Dr. G's explanation changed my mind about the Georgia flag and informs my opinions today on the debate over Confederate statues. There are statues that were put up to genuinely remember those who died - monuments at battle sites, perhaps the monuments at places like Lee's Arlington home. However, there are many, many others that were put up much later in defiance of segregation and in an attempt to intimidate minorities. Those do not have a legitimate reason to stay in the public view.

Atlanta Food Walks (@atlantafoodwalks) posted a very nice, reasoned, and informed piece on Facebook today that spun up this little walk down memory lane, and I had some interesting conversations with my Israeli colleagues on the topic as well. It is an interesting time and one that future generations will look to as a determination of our moral growth as a country and as a state.

Excuse the interruption.

The 21-Word Review: The Angry Birds Movie (Netflix)

If you set your expectations very, very, very, very, very low then it's not too awful. It's still not good, though.

Suburban 5-4-and-a-Door Solar: The First Bill

This week we received our first full bill since installing our solar array. It's strange to be excited about receiving a bill, but we were eager to see the impact of the solar array on what is typically one of our most expensive months for electricity.

The bill did not disappoint. July electricity bills in our household are highly variable due to vacations, camps, and other events that get people out of the home for long periods when the air conditioning is turned off or set higher. However, the lowest bill in recent records for July was over $280 with some exceeding $300. This month's $181 was a great improvement, even with the $2.82 penalty assessed by Georgia Power for generating our own power.

As expected, we did not make a lot on the excess power we generated. For the 166kWh we generated, we received $5.76 or about 3.5 cents per kWh. The rate charged for power ranges from 5.6 to 9.7 cents on our current plan, depending on use, so we obviously would prefer to use all of the power we generate rather than sell it back.

Here are the comparisons that matter. Since each bill is calculated over a different number of days depending on when the bill is generated, we have compared our usage and costs per day for the last five years.

In dollars, our average cost per day dropped from the $9-$10 range to $5.69. Not quite a 50% drop, but a very significant drop for a month with a lot of use.

In kWh, our average use per day dropped from the 60-70kWh range to 40.1kWh. Again, a nice drop to see in a hot month. We essentially maxed out production from the array (except when those summer storms rolled through).

What does this mean long term for ROI? It's way too early to tell. We'd like to hit 50% savings for the entire year to get our breakeven in the 10-11 year range, but that will depend on savings on sunny summer days as well as dreary winter days. The good news is that we are using almost all of what we generate and it is making an impact. The results from one month are not significant enough to determine a trend, so we'll have to keep watching for the rest of the year to get a full understanding of our breakeven point. In the meantime, it is still exciting to log into our array and watch it producing power and offsetting our usage and our bills.

For more posts about our solar installation, please click the "solar" tag below.

The 21-Word Review: Spiderman Homecoming

Not sure if I'm especially thrilled with Spiderman getting sucking into the Marvel cycle, but it was an entertaining movie nonetheless.

The 21-Word Review: The Passage Trilogy by Justin Cronin

I don't remember putting the first one on my wish list, but I ended up reading all three in a row.

Suburban 5-4-and-a-Door Solar: Early ROI Calculations

The number one question that we get about our solar installation is "how much did it cost?" The number two question is "what is the return on investment?" After less than a month of service, we don't know the answer to the second question with any certainty, but we can start making some estimates. Here's what we have calculated so far.

How much did it cost?

$13,466.24 net.

We purchased through a Solarize program that was very successful and reached Tier 6 pricing, which means that the price per kW installed dropped significantly over the life of the project. Our original quote was a $3.05 per kW installed. Our final price was $2.80 per kW installed. For our 6.875kW array (25 panels x 275 kW/panel DC rating), that puts the original price at $20,968.75 and our final price at $19,593.75 for a savings of 8.3%.

The federal government provides a 30% direct tax credit that we will be able to deduct next year.  In the state of Georgia, there are no state-level incentives. Including that 30% credit, our net cost for the solar array is $13,466.25.

Power/panel	275kW
Panels	25
Original $/kW	$3.05
Original Total	$20,968.75
Actual $/kW	$2.80
Actual Price	$19,237.50
Savings ($)	$1,731.25
Savings (%)	8.3%
Tax credit	$5,771.25
Net	$13,466.25

How many years until it pays for itself?

It is way to early to know for sure, but probably somewhere around 10 to 11 years. Less if the cost of power goes up and/or we are smart about our power use timing. We want to minimize power sent back into the grid and maximize usage of the power that we generate since the policies here are not favorable to selling power back.

Our annual cost of power has been about $2,060 recently. Due to savings, that number has dropped about 20% since we've been recording. See this previous post for details on the drop in use. (The graph below is a little smoother because I originally forgot to normalize to 365 day years and this is dollars, not kWh.) So we'll assume $2060 per year as the benchmark to calculating payoff.

Using a price of $13,466 and an annual power usage of $2,060 nets the following range of years for payoff.

Across the bottom are assumptions for changes in power cost. Those could be due to increasing rates (Georgia Power has hinted a significant rate hike to cover the cost of the failed Plant Vogtle, but nothing has been decided yet and rates in the past 3 years have been relatively steady), decreasing demand, or any other factor that would change the nominal cost of power in our home. The white line represents the current costs (100%). Increases in rates will push that line to the right.

The vertical axis represents how much the solar panels offset our power bill. We're expecting something in the 50% to 60% range, but really don't have any firm numbers yet since there are a lot of variables involved like power generation versus power usage over time each day, alternative pricing plans (e.g. time-of-day rates that benefit low usage in peak times), performance in the winter months, etc.

The colored bands represent number of years to recover the total cost of the panels. See the legend at the bottom for the ranges. Right now, we expect to be somewhere in the gray band, but we'll need much more data to be certain. It's something that we'll be watching over the next 12 months.

For those who care deeply about the math, we did not include time-value-of-money in the calculations since interest rates are very low at the moment. We also did not include financing costs since we paid for these in cash. The changes in power cost are for the lifetime of the system, not per year, as per-year made the model too complex and anyone who cares that much can back out the per-year increases from the final numbers anyway.

So, there's your answers as far as we know them today. Feel free to ask questions and we'll keep updating as more information becomes available.

Suburban 5-4-and-a-Door Solar: The Stub Bill

Georgia Power send us a stub bill for 10 days (June 20 - 29) to restart our billing cycle under the new solar paradigm. (Actually, they didn't send it. I went on line and noticed it just in time to get it paid. But that's another discussion to have on another day.)

We turned the panels on in the afternoon of July 27th, so this bill covers very little actual solar power generation. The 28th was a great generation day. The 29th was cloudy and rainy. However we do have a few new numbers to play with.

The bill showed that from the 26th to the 29th, we used 98kWh from the grid and generated 11kWh back into the grid. Not shown is how much we generated locally. Making a wild and completely unsubstantiated assumption that we would have used somewhere on the order of 120kWh on those three days (40 per day, three full days), that would mean that we generated about 22kWh on the 28th, 29th, and little bit of 27th. That seems very low (considering the calculations and data from the 28th), but that's the kind of numbers you get when you are working with a small, undefined set. We'll know more in a month.

What was interesting about the bill was that there is a 85 cent "Distributed Generation Meter Charge" that we didn't know to expect. We'll see if that's a flat rate or variable in the coming months. It's likely flat and pro-rated for the stub bill. We also saw that our Distributed Generation Credit (38 cents!) was subtracted after sales tax was calculated. No net metering here in Georgia.

The adventure is just beginning. After a few months we should know more. The July, August, and September bills are traditionally our highest, so they should give us the best numbers to work with and a better idea of expected break-even date and return on investment.

For a full list of articles on our solar panel installation, click on the "solar" keyword below.

The 21-Word Review: Swiss Army Man (Amazon On Demand)

We should encourage more independent films like this one. Well, not exactly like this one. That would miss the point entirely.

The 21-Word Review: The Girl with All the Gifts (Amazon On Demand)

It's a fungal, adolescent version of The Walking Dead where the actors get to use their real accents. Pretty good, actually.

Suburban 5-4-and-a-door Solar: Day 1

Two weeks ago, we finally got the electrical systems installed for our new solar panels (see more here).

A week ago, we got the formal inspection approval from the city.

Two days ago, after waiting a week for a call from Georgia Power, we called them to see if they were planning to come out and flip the switch to turn on the power. We discovered that (1) we could have turned on the power at any time, Georgia Power just might have seen some alarms that caused worry and (2) as of that morning our meter had been reprogrammed and we were welcome to turn on the power ourselves.

Which we did.

It took a while to get the wireless interconnection to the smart meter established, and the system needed to sit for a while to discover the panels. That meant that yesterday was our first full day with the panels online and the ability to watch them work.

We have been told that within the next week or so, the full internet capabilities will become available. The installer has to do some back-end work to set up a correlation between the readings and the panel locations, and we will have all sorts of fun data to play with when everything is complete. Not being an especially patient people, we logged into the system directly and spent the day watching production numbers. As the productivity of our system went up, our own productivity went down due to irrational exuberance over the numbers coming from the panels.

By the end of the day, we had collected about 200 power generation numbers. Without further ado, here's what they looked like over the productive hours of the panels.

The maximum power generation recorded was just over 5.5kW, which we were told would be about the maximum (AC) generation for our system. (The DC rating is about 6.9kW.) Those dots below the curve were probably clouds passing in front of the sun. Most of them lasted only a few minutes, and it's good to see that production didn't drop completely to zero.

At the top of the curve, we went out to our meter to watch it spinning backwards. It's a digital meter, so no spinner, but we could watch the LCD lines moving from right to left. Generally, we'd prefer not to sell power back to the grid since the pricing setup in Georgia isn't in our favor, but yesterday was a very bright day with moderate temperatures. When the real heat sets in, we probably won't be selling back much if any.

Doing some discrete integration on the curve shows that we generated around 27.5kWh during the time that we measured. According to Georgia Power, our peak usage in the summer is around 40kWh, rising to as much as 70kWh on some days. So it looks like we generated just over half of our needs on a typical peak summer day and a little less than half on a really hot summer day. But that's an oversimplification, of course, since no power is generated at night when we turn on the lights and the Netflix.

What does this mean for our power bill? It's too complicated to know right now, since power generation and consumption varies throughout the day. We should know more in a month and get a better view over the next year.

Today, we're not watching as closely since we have real work to do. We'll probably start watching again when the internet apps are enabled, but I suspect that this will all just be commonplace in a few months. Which is the point.

For a full list of articles on our solar panel installation, click on the "solar" keyword below.

The 21-Word Review: A Boy and His Dog (Amazon On Demand)

This movie has always been on my list of cult classics, especially for the ending. OK, now I have seen it.

The 21-Word Review: Mike And Dave Need Wedding Dates (Delta In-Flight)

There was less than 2 hours left and this was the only movie left with running time less than 120 minutes.

The 21-Word Review: Passengers (Delta In-Flight)

I thought this was marketed as a love story. It's more like a kidnapping story with robots, asteroids, engineering, and Morpheus.

The 21-Word Review: Beauty and the Beast (Delta In-Flight)

Dickens pioneered the concept of selling the same story multiple times. Disney has picked up the mantle. Not that I'm complaining.

The 21-Word Review: John Wick Chapter 2 (Delta In-Flight)

I love it when a movie creates a universe and does not need to spend half of the plot in explanations.

The 21-Word Review: Logan (Delta In-Flight)

I'm used to dark movies on a plane, but usually that refers to the lighting not the plot. Holy %&#$*@ cow!