I believe the only time that an upgrade could possibly increase the taxable value of your house is if the township/county knows about it (I.e., you got a permit to install it).
I also live in Michigan, but haven't researched renewable energy sources vs taxable value. I'm surprised to hear the gp say they had an increase.
Always claim you just replaced the switch. Just replaced the plumbing. Even then they can make your life miserable if they want. (I can go into most people homes and find multiple code violations--some homes just a few years old.)
These towns are trying to make money. In my town, if you take a few pictures and sell them on eBay, or elsewhere the town wants a fee from you--guess what, you're a Professional Photographer.
My point is these counties/towns are drunk with power, and preventing homeowners from upgrading their homes. They are looking for every dime they can extract from you. A simple electrical switch in you house will require an Inspector in you home at least two times.
If you feel an inspector is picking on you; pull your video camera out and tape every move they make.(Keep the evidence if needed in a lawsuit.)
A building inspector can walk into your home without a warrant at any time. That needs to change, along with enacting all these petty laws most people don't even know they are breaking. Stop passing their bonds, bonds, bonds, bonds, until they stop harassing us.
(It's up to an inspector if they feel the improvements added to the value of your home in the counties I have worked in. Try arguing with some guy who just just looks up codes, and given way too much authority.)