Comment by raphaelb

It depends on what your toilet supply lines are like and if you use a cold water only or a cold/hot water bidet, but a cold water only one (not nearly as uncomfortable as imagined before trying it) is very easy to install as long as your supply line has a shutoff valve and is relatively flexible.

It takes 15-20 minutes and it basically consists of unscrewing a few things and screwing them back together again.