10KW PV. 100+% ROI before I turned it on!
This isn’t a question but I feel close to the GBA community and wanted to share. I commissioned my 10KW photo voltaic system a week ago. It being fall in Michigan so far I’ve consumed significantly more power than I’ve produced. This condition should persist until Lake Michigan cools around February, but with net metering, next winter I should be golden. A year ago the utilities applied to end net metering but promised existing installations a ten year grace period. I got my net metering approval in time. My hip roofed house has poor solar potential so I built a 28′ X 14′ 1 1/2 story shed in back. A 10 in 12 roof pitch closely matched the recommended solar angle for my region. 20′ rafters and modest overhangs provided the necessary 20′ X 30′ area for 27 72 cell solar panels. 27 X 370W equals 9990W.
Marten almost convinced me that this was overkill. I scaled back my plan to 24 60 cell panels, but first I had to convince my electricity provider that I can use the power I produced. Eventually the house will get a energy retrofit with mini splits, but for now it’s heated with gas. Hot water was provided by a gas tankless. To boost my consumption I installed a used 30 gal electric water heater in series with the tankless, then turned off the gas unit. This is fine for our two person household but I when guests arrive I can turn the tankless back on for endless hot water. This provided nowhere near enough power increase to justify my proposed solar installation so we bought an off-lease 2015 Chevy Volt. I was surprised that our electric consumption more than doubled. I applied for and won a net metering contract for the 9990W system.
Utilities are notorious for being difficult to deal with, but DET Energy was anything but. Our power line was illegally close to the shed roof so we had it placed underground. I had them leave the last 20′ of the trench unfilled so we could put our solar cables in as well. DTE was responsive and courteous. At $390 I consider it a bargain. The co-generation application process is complex and really geared toward commercial installations. However, they provide a phone number for help. Someone always answered. By the time I was ready to turn the system on I only had a month before I’d lose my contract. In spite of the glut of people trying to beat the net metering and Federal tax credit deadlines they worked assiduously to accommodate their customers. They gave me the go-ahead with weeks to spare. The city was equally responsive. The code was written mostly with single inverter systems in mind so the requirements for microinverter systems are vague. Plus, PV systems are rare here so the inspectors are not fully up to speed. This was also my electrician’s first system. He brought and laid out the code manual to the inspection. It was fun to watch him and the inspector discuss and figure out which and where to put the various warning stickers.
So why was my system free? Two years ago when I first began research I quickly decided I wanted a microinverter system. I liked the shade tolerance and the inherent safety of no of high voltage DC lines, and that the system completely shuts down if grid power is lost. As far as wiring the array, everything is standard 220 VAC. The only additional components are a roof mounted fusebox that combines 3 20A microinverter strings into one 60A circuit and a shutoff switch near the meter. (Some states don’t even require that.) If system monitoring is desired a device is installed that talks to the microinverters individually. It communicates through the power line and a current transformer on one of the array power lines. It connects to the manufacturer through wifi. I installed mine near the electrical load center so it could monitor my total electrical production/consumption via optional current transformers on the main. As far as I know Enphase is the only company in the USA making such a system. I checked them out and was impressed with their products, support and stated company goals. I looked into their stock and it was trading at $1 a share. I bought a thousand. In spite of a big drop recently I’ve still made enough to more than cover the cost of my system. My next goal: buy a used Tesla Model Y and pay for it with my Tesla stock 😉
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