A reality based independent journal of observation & analysis, serving the Flathead Valley & Montana since 2006. © James Conner.
In its FAQ (PDF) on its Solar Utility Network, Flathead Electric estimates the annual output of a single 285-watt photovoltaic panel at 360 kilowatt hours a year (I’m assuming that’s AC kWhrs). This morning I ran a simulation of a fixed array of 356 SolarWorld 285-watt panels for Glacier Park International Airport that confirmed FEC’s estimated annual output.
I assumed a 30-degree tilt, a PTC rating of 258 watts DC per panel, and 10.8 percent in losses. My simulation generated an annual output of 338 kWhrs per panel, approximately six percent less than FEC’s estimate. FEC did not break down the output by month, but I did. Given I probably used slightly different assumptions, there’s no practical difference.
That’s the good news.
The bad news is that the more I look at this project, the less attractive I find it. The payback period is long, at least 20 years. In some situations, the investment may produce a negative return.
Tying the credit to the ascending block structure gives FEC an incentive to increase the base charge to minimize the cost of net metering credits. And because the credit on the panel investor’s bill is tied to FEC’s ascending block rate structure for energy charges, the biggest energy hogs will enjoy the best return on their investment. That does not seem fair.
If you’re thinking of spending $900 for a one-panel share of the array, read the fine print and check with a tax expert before making your decision. There may be reasons besides return on investment for investing in a panel, but if your objective is simply saving money, you may not like SUN’s economics.
