Quote Originally Posted by Lampada View Post
Я бы всегда вставляла "и" между целым и дробным.
I think the “rules” (if you can call oddities of colloquial speech “rules”) are a bit more complicated here.

If the integer part is 0, «и» is almost never used. E.g. «0,2 В» is pronounced as «ноль два вольта», not as «ноль и два вольта».
If the integer part is grater than zero and the fractional part consists of a single digit, then it's almost always pronounced with «и». «1,2 В» is «один и два вольта», not «один два вольта».
Finally, if the int part is > 0 and the frac part consists of several digits, then both variants are acceptable. «1,75 В» is pronounced as «один семьдесят пять вольта» or as «один и семьдесят пять вольта».