One Year – Let’s Run the Numbers
This is the first anniversary of the first successful meter reading by PSE&G after activating the panels. That means that we can run the numbers.
All values are kWh. This year’s date is 7/21/2005 – last year was 7/21/2004.
Inverter 1 This Year: 4279 Last Year: 677 Total Inverter 1: 3602
Inverter 2 This Year: 3544 Last Year: 565 Total Inverter 2: 2979
Total Solar Generation: 6581
Meter Out This Year: 8724 Last Year: 1365 Total Bought: 7359
Meter In This Year: 4823 Last Year: 564 Total Sold: 4259
Net Metering Purchase: 3100
Total Electricity Use = Total Solar Generation – Total Sold + Total Bought = 9681
Solar Generation Percentage = Total Solar Generation / Total Electricity Use = 68.0%
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Our installer predicted that we’d generate 2/3 of our usage. He was pretty much dead on – the real numbers are just a smidge better than that. Additionally, we reduced our utility demand by that much – reducing utility pollution.
When it comes to dollars, we actually did better than these numbers show. PSE&G rates increase above 600 kWh per month in the summer. Our usage allows us to avoid going over 600 kWh net purchase per month, avoiding the higher rates.
Our savings works out this way:
Green Mountain Energy Supply Charge: $0.07508 / kWh
PSE&G Delivery Charge: $0.0.30305 / kWh (the lowest rate – it’s higher above 600 kWh in the summer and higher in the winter as well at $0.0384/kWh)
Total Rate: $0.10539 / kWh
Our Savings: $693.57 for one year
That would produce a 23 year payback but with the added $1251 from the sale of the SREC, it’s a 8.5 year payback.
And the air is cleaner.
Comments
7 Comments on One Year – Let’s Run the Numbers
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Rick Brooke on
Fri, 22nd Jul 2005 5:34 pm
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amazingdrx on
Fri, 29th Jul 2005 6:57 pm
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Troy Cawley on
Fri, 21st Oct 2005 11:16 am
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Steve Carlson on
Thu, 23rd Mar 2006 10:50 am
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Jeff Saunders on
Sat, 19th Aug 2006 5:39 pm
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Clee on
Thu, 16th Nov 2006 7:56 pm
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Atila - Solar Power Expert on
Mon, 24th Dec 2007 6:40 pm
Mark,
Wow, this is a thorough economic analysis and it is great feedback on system performance. There is no doubt the SRECs put the economics of PV into a very acceptable range. As electric rates increase over the next 5-10 years, I think the simple payback will come in around 7.5 years or less. If you take into account that the system is a home improvement and adds value to your home, the electrical savings and SRECs become tax free dividends for the next 25 years. Thanks for providing this info.
Rick Brooke
Excellent! That payback is for your part of the system cost of course.
I’m wondering how the payback would change given solar heat from the panels collected as a byproduct for domestic hot water heating and home heating in optimal seasons in your area, spring and fall.
I will blog this up. Great work!! Saving fossil fueled energy is patriotic in these troubled times.
Mark,
Some more information for refuting the claims that you are not reducing energy use…
Another benefit of your solar system is that it’s peak output is achieved during peak demand. This has the effect of “shaving” the peak. You won’t realize this on your electric bill until many more people shave the peak…and then we don’t have to build that next “clean coal” (yeesh) generator to supply those megawatts.
That’s why the state is giving away money for solar and why the electric distribution comanies (PSE&G, AC Electric, etc.) SHOULD get involved. They can also realize savings by not having to build that next transmission line…they’ll save millions in capital costs and PR!
Thanks for the blog.
Troy
The air is not cleaner cause you sold your SREC credits.
Found this information on installing a ceiling fan – also very energy effecient!
Mark, you are (as you probably know) underestimating your electric bill savings by saying that they are all worth the minimum $/kWh that PSE&G charges you. You may find your pay back is significantly shorter than 23 years if you calculate what your bill would have been if you had no PV and PSE&G charged you for those extra 6581 kWh and charged you extra for usage above 600kWh/mo.
For our PV system, I calculated and compared what our bill would have been
* if we had no PV,
* with the PV (no change in billing rates)
* with PV with Time-of-Use billing
(see last chart on http://www.apricot.com/~clee/solar/DataCharts.html )
I also calculated for each month, how much we saved per KWH.
It is a bit of a pain doing all these calculations. I created an eXcel spreadsheet to help me, but I have to make changes to it every time PG&E changes their calculation method or changes their surcharge rates, which could be quite a few times per year.
I have found that while the basic rate for the first KWH hasn’t changed, the surcharges (when you use more than a certain amount of KWH/day) increased so much, it eclipses the basic rate. On a summer afternoon I could be paying as much as 53 cents/KWH. So while the base rates haven’t changed, we’ve gone from saving an average of 20 cents/KWH in the first couple of years to saving an average of 30 cents/KWH last year. This year is starting out even higher.
(see last chart on http://www.apricot.com/~clee/solar/DataMultiYear.html )
Every time the surcharge rates go up, our payback period gets shorter.
Have you figured out yet if you would gain from changing to the Time-of-Day billing?
Great analysis! Nice work 😉
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