Our first Megawatt-hour

So, in September 2014, we signed a contract to install a photovoltaic solar panel array on our roof.  It took quite a while to get things complete, but we “threw the switch” the first week of March 2015 and by 1 May 2015, we’d generated 1 Megawatt-hour of electricity!  Woo hoo!  The trip has been full of frustrations and surprises, so I thought I’d document it a bit here. I can just hear your confusion: “Why on Vex::Tech?! Isn’t this supposed to be about virtual worlds and stuff?!”  Well, true… so I’ll make the totally weak excuse that it is helping to power my own opensim and HiFi servers as well as the various gaming desktop and laptop machines in the house.

The basic plot is that we were turned down by one of the local “zero-down” solar companies because we’ve got a little gable on the south-facing side of our roof.  Since these companies are all about, well, making money from generation, they really want to maximize efficiency. The way they work is basically to install a PV system on your roof (for free) and then lease it back to you. Since they are the owner of record of the system, they get the government incentives and energy credits while you get the energy reduction (I think you get all of it – even if you make more than you use, you get the payments from the electric company). But the gable in our roof disqualified us, at least with the vendor we talked to.

Instead we purchased our system outright. The installer installed the whole thing and acted as a general contractor for electrical work and such.  Yes, if our roof didn’t have that pesky gable we probably could have fit another 6 panels up there and had a bit less shadowing in the morning and afternoon, but it is still working out to be a good deal.  A HELOC funded the initial installation, though we got back nearly half of the cost in tax breaks and installation incentives.  The energy savings is … dramatic.  The installer predicted that our panels would, on average, generate about 60% of our power – so far that looks somewhat low, but perhaps our weather has been unexpectedly good.  In addition, every megawatt-hour we produce gets us a free “solar renewable energy credit” (SREC) which can be sold on an open market to people who want to offset non-renewable energy production/use. The bottom line is that we are expecting break even in about four and a half years, between energy savings and rather conservative estimates of SREC value.  Couldn’t be more pleased.

Our system, by the numbers:201504UsageHistory

  • 14 300W panels
  • 3.8kW Inverter
  • 25kWh produced per sunny day (more or less)
  • 500kWh produced per month (so far)
  • 22.1kWh used per day in April 2014
  • 3.8kWh (net) used per day in April 2015

We’ll see how things go, but we’re darn happy with it so far!