I talked a little in the past on the difference between micro and string inverters and laminating about spending the extra money on micro inverters. All of our panels are facing the same way and we have no shading, so our house is the perfect candidate for string inverters. The same 5.1 kW solar system would have cost us $8K to install with a string system saving us $2K off from our micro inverter system.
Here is a month by month breakdown on what we actually produced and the maximum that a string inverter would have produced. I am calculating the string production off of the output from the lowest panel for the month which does not account for hour by hour variances when that panel was not producing the lowest amount of energy.
|Actual Production||String Production||Difference kWh||Difference %||Bill Savings||Payback|
|December||423 kWh||243 kWh||180 kWh||42.50%||$41.25||48 Months|
|January||414 kWh||245 kWh||169 kWh||48.81%||$38.72||52 Months|
|February||566 kWh||426 kWh||140 kWh||24.73%||$33.10||60 Months|
|March||704 kWh||647 kWh||58 kWh||8.10%||$13.32||150 Months|
|Year||6321 kWh||4683 kWh||1611 kWh||25.49%||$379.17||5.3 years|
December (Nov 21 – Dec 21)
Here is what the monthly output looks like for our array. In a general day our panels start producing power at 7AM and stop producing at 2PM. From 2-4PM each panel is putting out 1-20 watts so they are kind of producing, but I am not counting it. When I look at the panel by panel production on an hourly basis from 7-11AM each panel is producing about the same amount of power, but after that there is significant shading in the lower left of the array. That area might be producing 20 watts compared to the other ones doing 250 watts. I did look closer outside and at our solar report from roof orders and both confirm that there are trees casting shade on our solar array. December is in the middle of the winter solstice so the sun is going to be the lowest of the year. I can’t say what the rest of the year is going to bring, but so far I feel good about going with the micro inverters.
January (Dec 22 – Jan 21)
The day to day solar activity has been the same for January as it was for December and based on what it is looking like it will probably be this way for February too (maybe even part of March). In general on clear day our solar is producing 15.2 kWh a day from 13.8 kWh last month, but we have had cloudier weather this month so the overall production is down.
February (Jan 22 – Feb 21)
The days are not getting much longer, but the eavning shading is a lot less. I am hopping by the end of next month there will not be any more. That would mean that 6 months out of the year we would be getting shade which means it is a good thing that we got micro inverters. Also a word to the wise would be to plan you solar project in the winter because I would never have guessed that those trees would have ever caused shade on our sheshed when I was re-roofing it in the summer.
March (Feb 22 – March 21)
Two things to note this month. Since this billing cycle hits the end of February there was only 28 days in this cycle; also daylight savings happened so the times are going to be an hour off. We are starting to produce solar at 7:30 am and then from 9-10am some shading rolls across the panels were we have some panels producing 50w and other 100w. After that it is smooth sailing and our system peaks out at 4.7 kw (it’s a 5.1 kw system) at 1:30pm which is a lot better than January were it peaked out at 3 kw. From 4-5pm we are still getting shading from those trees, but only on the lower panels. From there everything fades out until 6:30 when the panels go dark.