First month of solar

First month solar

First month graph of solar power

The solar array was turned on for real 30 days ago; in that time, it’s produced 389 kWh of energy, which covered 96% of our usage for the month.  I’m pretty pleased with this! As compared to household use, it was:

  • 389 kWh gross production, of which
  • 230 kWh net was pushed out to the grid (meaning 389-230=159 kWh were used directly), and
  • 245 kWh net was drawn from the grid

So, we used a mere 15kWh more than we made.  I blame it on my niece’s baking in the electric oven ;)  (and the need to run the dehumidifier a few days; it was very rainy).  404kWh for the month was actually a fair bit higher than the last several months; the other big hitter was running the fans a lot due to the heat.

In terms of daily output, we saw:

  • Peak power output of 2185W (I think this is due to a 199W limit on each microinverter)
  • Maximum daily energy – 18kWh (on the first day of operation!)
  • Minimum daily energy – 5kWh
  • Average daily energy – 13kWh

What I really miss now, though, is the whole-house energy monitoring that I had; we climbed in usage last month, and I can point to some causes, but I’m flying blind now.  I’ll have to break down and buy a Ted 5000 if I don’t manage to put together my own monitor with CTs soon.

13 thoughts on “First month of solar

    • Simon –

      Well, so I made about 400kWh of energy this month. I pay roughly $0.10/kWh, so that’s $40 worth of electricity. I got a lot of incentives to do the solar from state, federal, and utility. So my end cost was quite low – about $5000 in round numbers. Assuming no increase in electric rates, this would be about a 10 year payback at 400kWh/month – although the winter months will be less, and utility rates will go up. But let’s say 10 years in round numbers, and the array should last at least twice that long.

      But to be honest, cost wasn’t my primary motivation. True, I probably wouldn’t have done this if it were fantastically expensive and there was no payback in sight, but I also thought it was the right thing to do from an ecological perspective. We just can’t keep digging stuff out of the ground and burning it to live the way we do, and I was in a position to change that at least for my household. (Plus, it’s geeky techie stuff that I love!)

  1. Oh, I know cost isn’t generally the motivation for doing things like this, but it’s certainly a factor. Even for the keenest and greenest, it’s easier to justify spending money when the investment pays for itself in ten years, instead of being something you’ll spend the rest of your life paying for.

  2. Jon, yeah I saw that. I can’t actually use it; it works on the same principle as the homebrew one I made, by watching an IR pulse every watt-hour on top of the meter. My new net-metering meter no longer has that pulse (well, it does in diagnostic mode, which involves strapping a magnet to the side of the meter… pretty sure my friendly meter-reader would freak out at that).

    The Blue Line PowerCost Monitor WiFi edition (which you link to above) seems pretty decent, though, and very easy to hook up. But for about $250-$270 for the whole package, I think I’d much prefer the Ted 5000 for $200 (no remote screen) or $240 (remote screen). The only downside is a more invasive install, and an questionable design decision to get the data out via powerline comms, which may interfere with X10 and/or my solar inverter monitoring.

    The Brultech ECM monitor for less than $200 also looks very interesting, but much more of a hacker device for now (zigbee and/or serial and/or ethernet over serial etc to communicate with the device). If it had a built-in webserver to retrieve data & configure, it’d be swanky.

  3. Eric-

    Thanks for sharing this. I installed a 12 panel (2.7kW) enphase system on my garage in Minneapolis in May. I did the work myself and thus could not collect the state money, but the Xcel rebate and Fed credit brought my final cost to about $1200. Payback in 3-4 years. One question I have for you, do you see a difference between the enphase reported generation and the net meter from Xcel? I would say that there is a 5% undercount on the Xcel meter, or I guess a 5% overcount on the enphase. Do yours match?


    • Hi Jonathan!

      Wow, that’s awesome. If my roof were lower & flatter I might have tried that… $1200 net for a 2.7kW system is phenomenal.

      My Xcel meter currently says 402kWh, and the Envoy unit says 420kWh. I had about 2kWh on the Envoy unit prior to meter install, so it’s a difference of 4%, with the Envoy reporting high.

      I don’t think there’s any conspiracy here; I’m sure the Enphase monitoring isn’t revenue-grade, and I think sometimes it interpolates if communication is lost with the inverters. However, I also wonder about the Itron meter they put in; in reality the array often isn’t putting out that much, and I wonder how accurate the meter is over its range. I hope to eventually put in a current transformer monitoring system, and get a 3rd datapoint for the production.

      I’ll have to look for your array on the Envoy public sits, if you’ve got it there. I’m very impressed that you did it DIY!


    Above is my Enlighten link. The panel install was pretty simple, although reaching all the bolts was kind of a “paint yourself in a corner” problem since I covered about 90% of the roof with panels. I did 80% of the work alone, and had some friends help with carrying the panels up and bolting on to the roof since they are pretty big and fragile. The rest is just running wire and meeting code, which is not too complicated once you figure out what is required. My local inspector was very helpful in that regard as the lightning protection and grounding process is a little different than your typical interior wiring project.

    Based on the quotes I got for the install from the pros, bidding something like $2-3 per watt just for labor, they are billing >$200 per hour on a simple project like mine. Something higher and steeper might end up taking more time, but I think this is a gravy job if you can get the work.

  5. Jonathan, grounding & lightning was also a slight hiccup for my installer once the inspector came. :)

    The subcontractor electricians who actually did my work had never done it before, so I did about as much research as I would have needed to, had I done it myself, I think. It’s still worth at least $1k to me to not be on my roof, though ;)

  6. I have a TED 5000 system monitoring my utility and solar feeds. It works well but the power line comms make installation a bit finicky. I had to add a wireless access device to allow the gateway (which picks up the power line signals and networks the data) to simultaneously talk reliably to the power sensors and my wireless router. If you get one, let me know and I will share a few lessons I learned on the way! Don’t get the remote display!

  7. Peter, thanks – I was worried about the powerline comms interfering with my Enphase inverters… I’m currently experimenting with building my own arduino-based monitor based on and a fairly tidy prototype of my breadboarded circuit can be seen at in this photo. I will need to cram in burden resistors for 3 more CTs at least, though. May have to take it off the tiny breadboard. :)

  8. Eric;
    I have a 3400 watt enphase system on my house for a year now and it’s been almost flawless. I recently installed a TED 5000 with 4 CT’s and it has not interfered with the enphase communications although it does wickedly interfere with X10! I don’t care about the X10 but I have had trouble with the data presentation of the TED 5000. When I’m producing excess power it always adds my usage and production. I think that it should represent the net power usage i.e. production – usage. Am I wrong?

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.