Saturday, August 05, 2017
Thursday, August 03, 2017
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.
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.
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.
Monday, July 17, 2017
Friday, July 14, 2017
Tuesday, July 11, 2017
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.
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.
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.
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.
Sunday, July 02, 2017
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.
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.
Saturday, July 01, 2017
Friday, June 30, 2017
Thursday, June 29, 2017
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.
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.
Wednesday, June 28, 2017
Tuesday, June 27, 2017
Monday, June 26, 2017
Saturday, June 24, 2017
Friday, June 23, 2017
Thursday, June 22, 2017
Wednesday, June 21, 2017
Tuesday, June 20, 2017
Monday, June 19, 2017
Friday, June 16, 2017
Thursday, June 15, 2017
Suburban 5-4-and-a-door solar: We have electrical hookups!
As of this week, we have electrical hookups to our solar panels. Nothing's turned on yet, as we are awaiting approval from the city inspectors, but at least all of the hardware installation is now complete.
Here's what we have in place. It's not at all intrusive.
First, there are the solar panels themselves. Feel free to stop by and take a look at them. You honestly wouldn't notice them if you weren't looking - they show up much more prominently in this picture because it was taken from a drone. There's a tree in the front yard that hides them from most passers-by. Not that we're ashamed of them. We kind of like the way they look.
The outside of our house used to just have that one meter on the right - the typical spinny-wheel thing. Now we have two additional boxes, one that combines the sources and one that is an emergency shutoff / breaker specifically for the solar circuit.
Here's what we have in place. It's not at all intrusive.
Inside the box on the left are the combined connections and a cool internet-enabled meter that is purported to have an associated app that will allow us to see how much power we're pulling from the grid and how much we're pulling from the solar panels. It's purported because we aren't allowed to turn it on until after inspection completed.
The box on the right has some very large fuses and a big on/off switch straight out of Dr. Frankenstein's lab. We assume that this is used to shut off power from the solar panels when service need to be done on the house. We will confirm that before turning on the system - and we will find out if we need to keep large fuses in stock, just in case.
Inside the house, all of the wiring was very expertly run inside conduit like these, carefully attached to floor joists. The power feed from the panels on the roof was run down a utility chase from the attic to the fuse panel in the basement. It took a little while to get everything run, but the results look great and there are no wires on the outside of the house.
On the breaker panel are warnings that there is a photovolatic (i.e. solar) power source on the house. Again, this is for safety since turning off power from the grid no longer means turning off power to the house. (Not that we can actually use power when the grid is off. For safety reasons, we don't want to be generating power back into a downed wire so the system is designed to shut off when the grid goes down.)
There are more warnings inside the breaker box. We were actually tapped out on the breaker box, but the installer was able to put in some half-sized breakers and expand the capacity without installing a new box.
Overall, we are very happy with the results so far and are eager to get the system running! It's starting to get hot out there.
For a full list of articles on our solar panel installation, click on the "solar" keyword below.
Wednesday, June 14, 2017
Tuesday, June 13, 2017
Monday, June 12, 2017
Friday, June 09, 2017
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