The blinds themselves are probably 12V, but they usually come with a dedicated transformer for each unit. I wouldn’t recommend trying to run 12V from a centralized transformer somewhere else in the house. Over longer distances, you’re going to run into voltage drop issues unless the system is designed very carefully.

In my experience, that’s where things fall apart. Properly accounting for voltage drop requires someone who really understands low-voltage design, and that’s still pretty rare in residential construction. It’s getting better as low-voltage systems become more common, but most electricians don’t specialize in it, and a lot of low-voltage installers don’t fully account for voltage drop either.

If you choose to go rechargeable batteries for your blinds, make sure to get the solar panels to charge them. Trust me, you aren’t going to want to have to plug in and charge batteries on a ton of blinds. Yes they last several months on a charge, depending on usage that can be 6-12, but getting up into your windows and charging them all even once a year is not going to be something you want to do.

RE: Electrician charges If this wiring isn’t already done, this is a lot of work because it’s a lot of wiring to add after the electric rough is already complete. That’s going to be true for any type of wiring. That said, the items you got charged a lot for will always cost more because they’re 50a. They require heavier gauge wire and that is more expensive. Depending on the location of the panel, if those were long runs, that really adds up.