ROI for Residential Solar Power
By Jim Trudeau
December 30, 2013 So, Jessi and I have a lot of motivations for “going solar.” This isn’t all altruism about reducing carbon dioxide added to the atmosphere. What is the return on investment here? Is this a reasonable thing to do, regardless of the goodly green-ness of the idea?
Keep in mind, this is fundamentally an anecdote. This is information about us, our home, our electric consumption, and so on. This will not apply directly to you or your circumstances. Draw your own conclusions, but you’ll see that for us this was a no-brainer, once we looked at the numbers.
Over the course of the coming year I’ll have real data. For now, let’s rely on estimates. These are from the solar provider, but come from PVWatts, which is THE model for estimating solar output. It takes into account your local weather, the angle of the panels, their orientation toward south, and just about anything that can affect power output. I used it myself directly when I discovered it, a neat tool.
Over 12 months, we should generate 14,574 KWh. Since all such estimates have errors in them, for round numbers let’s call this a production of 14,000 KWh. We’ll be conservative. (BTW, that’s 14 MEGAWATTS of power, ain’t that a cool number).
The system is 40 panels each producing 260W nominally, for a system rated at 10.4 KW. We are using micro inverters, and the panels are flat on our roof. 24 panels are at one angle, 16 at a shallower angle. They will probably do better in summer, the 24 at a steeper angle will do better in winter, but we’ll see.