I currently have Liberty Mutual for both my home and car insurance. I assumed that since Liberty Mutual is the partner with "InsureMyTesla" that they would have good rates. Bad assumption. I live in northern NJ, we are home owners, and have a clean driving record. Liberty Mutual quoted me $3034 annually to add the Tesla Model S 75D we ordered and a family car with both my wife and I on the policy. Progressive quoted me $1546 annually, with the same and slightly better coverage details. I checked Geico too, they were closer to Progressive, but more expensive (around $1850 per year). I might have gotten Geico a little lower if I'd added the home insurance to the package, but I had already figured out Progressive was going to be cheaper overall, and their website worked better and gave line item transparency on the quoting functionality. I went with Progressive.
I should get my first Tesla in 2-3 weeks, it is currently in production!