The current billing period beginning on March 2, has been extremely productive. As you can see in the chart from my utility, the gray bars that dip below the 0 axis are the days my solar panels generated more than I used in my home.
The statistics for the period are revealing. The overall average was 108 percent, which included a low of 41 percent and a high of 152 percent. 19 of the 28 days, the system generated over 100 percent of the energy used.
My electricity bill for the last 12 months is $540.70. That averages out to $45.07 a month. If I assume that my monthly bill used to average around $250 a month, that is an annual savings of $2,459.30 a year. My solar panels have been operational for 11 years. That means I have saved a total of $27,052.30 over the period. Add in the $17,600 incentive received from the state on installation 11 years ago and my solar panels have generated $44,652.30 over the past 11 years.
Here’s an update on the performance of my solar panels this year. My new mini-split A/C is paying dividends by allowing me to cool my bedroom at night to a comfortable level while keeping the rest of the house at a higher temperature. The days are getting longer and I am optimistic about the next three months, normally the most productive ones of the year.
Milder daytime temperatures since the hurricane have reduced consumption from air conditioning, along with a lot of cloudless days have resulted in higher percentages of energy being produced from my solar panels. The chart on the right shows that over the last ten days, percentages generated from solar have been near seventy percent on average.
Hurricane Irma came through Florida the weekend before September 11, 2017 and did massive damage throughout the state. It lost its tropical characteristics after 11 days and traveling 4,000 miles. Half of Palm Beach County, 500,000 people are without power.
I am running completely on my photovoltaic system and have been for two days now. This is the first extended operation of my system in emergency mode and it has been interesting. We, my step-daughter and her husband, sheltered in place. We lost power at about 3:30 in the afternoon on the day the storm went up the west coast of Florida. The system switched to battery backup which carried us into the next morning until about 3:30 am.
When the sun came up the next morning, the charge controllers directed all of the energy from the solar panels to the battery bank. We had no power in the house while that was taking place. That was because we lost power in the afternoon and it was cloudy and stormy. Also, we didn’t have a good idea of how to manage our consumption. My children have returned to their home so I will be consuming much less tonight. It will be interesting to see how things perform. With careful management my house is powered for about 12 hours on the battery backup.
So, what can I run on emergency power from the solar panels and/or the battery backup? Pretty much everything in the house except for air conditioning. With the tight envelope this house has, impact glass windows with low-e reflective glass and good insulation in the attic, the house stays around 80 – 83 in the day and cools down at night. It’s quite comfortable sitting under a ceiling fan. I am definitely not uncomfortable or suffering. This, after all, is what we designed and implemented the system for. It is basically functioning as a generator would, but with no noise or fuel. Additionally, it runs every day all year long, generating power. It will eventually pay for itself while a generator never would.
Yesterday was so clear and cool that I think the charts from my house might represent an ideal system maximum for March 17th at this location. March 16th, the day before yesterday, was almost identical.
This chart reveals that night time usage runs around .5 kWh. That’s got to be phone chargers, DVR, and some other “phantom” loads from various small electronic devices that are plugged in. The increase in usage just before sunrise is my irrigation system coming on.
The percentage of total electricity used from my solar panels was 108. Yesterday and the day before the totals generated for both days were exactly 24.7 kWH. That’s why I think this is a good measure of the maximum my system can generate under ideal conditions in mid-March. Because of differences in my usage, there is a slight difference in the percentage generated for yesterday and the day before.
The last ten days are shown below in both graphic and tabular form. So far, we have had three 100 percent plus days and one 90 percent plus day.
Yesterday, March 3, 2107, was overcast and gray all day long. We even had some light showers. It was probably a worst case day for solar energy generation. Even so, we generated 28 percent of our energy from the sun. This ends. a series of very good days up in the 80 percent range. Our best days are ahead in the months of April and May. My energy efficient window replacement project should be done by then so I am optimistic about how well the system will perform then. The time-lapse for the day reveals some opportunities for generation were available in the morning.
January 29, 2017, was cold, cloudy, and rainy, a worse case scenario for our photovoltaic system. I stood the chill as long as I could, but finally gave in and turned on my electric heat. Because of the clouds, our solar panels only generated 1.9 KWH of energy while the heat used over 30 KWH. The percentage from solar shown in the chart is the result. The chart below shows a very atypical day where all of our energy came from the grid and none from our solar panels.
The chart below shows the last ten days of percentage from solar. We were doing quite well actually until the cold front came down and stalled over us.