A lot of people like to throw the word "utopia" around, especially where solarpunk visions are concerned. But it's not really a good word to use, for one big reason – a utopia cannot actually exist.
The word utopia itself literally means "no place" because it's a philosophical ideal. In reality, it's unattainable. The reason why is pretty obvious when you think about it. A place which is perfect for one person may not be perfect for another. Ask ten people for a detailed description of a perfect world, and you'll get ten different answers. Some of them may even be horrifying when you consider the implications.
OTOH, the word eutopia (which is a homophone, confusingly) simply means a place which is good. A world does not need to be perfect to be a good place to live in. It may not be perfect, but that's ok. Perfection is a very western ideal anyway.
Basically, if you'll excuse the comic book reference, think Black Panther's Wakanda, not Wonder Woman's Themyscira.