Some sharp-eyed readers have noticed that while I am faithfully documenting the kilowatt-hour power production of my rooftop solar array, I haven’t spent a lot of time discussing the money the panels are saving me. So in today’s post I take a sampling of bills paid to Puget Sound Energy for electricity in the years 2013-2015. It looks like going solar is slashing my electricity bill by about 60 percent.

In each of the three years I looked at a seven-month range of bills spanning January to July. I figured this would give me a good mix of winter and summer, short days and long days, so as not to skew the results too wildly in either direction. During this span of months in 2013 and 2014, I didn’t have solar panels; during this span in 2015, I did have solar panels.

From January to July of 2013, I paid PSE $317.86 for electricity, or about $45.41 a month. For the same months in 2014, I paid $303.97, or about $43.42 a month. Looks pretty consistent for the pre-solar figures.

However, from January to July of 2015, I paid PSE only $129.13 for electricity, or about $18.45 a month. That figure includes an administrative fee and tax amounting to $8.30 a month, which will always be applied no matter how much electricity the solar panels generate. Some homeowners begrudge the utility this fee, but I actually don’t. I understand that there’s some overhead involved in managing my account.

While we’re talking money, too, it’s important to remember that in the state of Washington, utilities send solar users a check once a year based on annual energy production of the customer’s array. In my case, PSE will be sending me a check for $498.30, based on 3322 kilowatt hours generated.