PV Production Info

These images are from an Excel spreadsheet I created to keep the details of the power production for my own reference. It also will provide me with a visual image if something goes wrong with the panels since the numbers will not fall into the 'range' of daily production.

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Daily production vs average daily use

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Daily power production read from the meter

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Values from each PV string as read from SMAs

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We invested $10,022.60 to produce the first kW! That is the total cost of our project. Taking into consideration that cost, the Green Mountain Power payments for the power the panels produce, the reduced monthly power bill, and the reduced cost per kW as the panels produce more we're doing alright already. Currently the 100th kW averages out to just $96.62 per kW. 200th - $48.31 and dropping fast. By the time we produced the 1,000th kW it was down to $9.66! As of 14 May 2012 it was down to $1.76 and falling more every day.

Here is another detail. The house panels are at a 'better' angle to the sun then the porch roof panels. The house gets a little more sun also. Since the panels are higher fewer shadows come into play. The house panels are producing at $1.65 per kW while the porch panels are producing at $1.94 per kW.

My panel foot print now has a 250 watt production version.

While the 240 watt I purchased was the highest production capacity at that time there are panels with a little larger foot print now up to 300 watt capacity. That is a 25% increase in production capacity in just over a year and a half.

All the above may give you the wrong idea. Every one of those kW also saves me money at $0.14728 per kW currently, up from $0.13841 in Jul 2010, since I am not paying for GMP's grid power and if I don't use it directly, it goes back on to the grid for someone else to use which runs my utility meter backwards! So the same 1,000 kW will also save me $147.28 off my power bills at current cost per kW. For 2010 (from 16 Jul 2010) we averaged 185 kW per month. To get all the data see the chart for a month by month break down. 2011 averaged 239 kW per month. March 2011 production, 299 kW, beat every month in 2010 except August which was 331 kW. And August had an average 13.98 hours of daylight while March had an average of 11.95.

Details on my on going light bill may be viewed by clicking here. Keep in mind that the utility charges fees for 'Customer Charge', 'Water Heater Rental', 'Storm Adjustment', 'Energy Eff. Chg', and 'State Sales Tax'. These fees amount to over $23 each month as part of the bill. It won't take that long for this project to pay for it self at the current power rates. As the rate goes up our costs come down even faster.

At $16.67 for my April 2012 power bill not only did I pay for no power from GMP but the power produced also reduced the fixed costs by 28.7%

Power production by month

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Monthly power bill

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Weekly growth total of Kilowatts produced

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Now for that maple tree I mentioned on the Home page. It is visible in the picture above.

I planted that tree when we moved into the house in 1975. It has survived a major branch broken when the tree was young when a neighbor's child was climbing it. More recently a big gust of wind took out another large limb, not visible from this angle.

In 1989 I put up the ten foot satellite dish. For 21 years we had an average cost for our TV service of around $100.00 per YEAR, about $2,100.00. If you place the average cable TV bill at $50.00 per month that's $12,600.00 for the same period. That savings of $10,000.00 paid outright for this solar project. The 4DTV ESR still brings in 'in the clear' channels but the choices for 'scrambled' channels are getting fewer every year. As the maple grew I also began to loose satellites. I vowed never to cut the tree down just to get TV. Now I'm faced with another dilemma. The tree casts its shadow on both PV strings late in the day.

So! do we cut it down for the sake of a little more power production or leave it for the CO2 it captures in the growing?

Leave us your vote in the guestbook!

Here's a tid bit to chew on.

Over 25 years, an average home can save $55,000 with a solar electric system.

The Appraisal Journal reports your home value increases by $20 for every $1 you save on your electric bill annualy. Save $1,000.00 on your light bill and see your home rise in value $20,000.00!

The system I have had installed will realistically save me between $400.00 and $500.00 (about half) on my annual electric bill. That translates out to an $8,000.00 - $10,000.00 rise in the value of my home. I did a presentation before Barre's City Council and if all goes well that increase will not increase my taxes at all. The best of both worlds.

Using information from my past Green Mountain Power bills I have calculated the following based on our home's electrical power usage vs. the national average.

Before any conservation effort.
2004 - CO2 emissions from the electricity use of 0.880 homes for one year, 15,620 pounds of CO2, 10,232 kWh from GMP. This means that even before we started to reduce our consumption we were using less than the average household in the US. About 12% less!

After efforts to reduce usage but before PV solar panels were installed.
2009 - CO2 emissions from the electricity use of 0.574 homes for one year, 10,120 pounds of CO2, 6,675 kWh from GMP. This reflects about a 35% savings.

First full year using PV solar generated power.
2011 - CO2 emissions from the electricity use of 0.329 homes for one year, 5,720 pounds of CO2, 3,828 kWh from GMP. This reflects a 62% savings from the 2004 consumption rate!

The panels saved 4,800 pounds of CO2 for 2,864 kWh produced in 2011. The CO2 savings generated by the PV solar panels equates to 83% of the CO2 emissions for the power we used from GMP!

2012 We have used 796 kWh from GMP while the panels have produced 852 kWh as of 17 Apr 2012. The GMP meter went from 37702 to 38420, 718 kWh. 78 kWh backed out completely by the Net Metered configuration. Since the system is averaging 38% feed back it means 324 kWh were pushed out to the grid and over night only 246 kWh were used again.

PV Panels on my home