[Closed] Inside vs outside FTP?

Anyone find a noticeable difference between their inside (rollers/turbo) FTP and what they can achieve when outside? Finding my 20 min power down by up to 10%, wondering if others find something similar and what you do when training indoors, do you just set it lower for the likes of Trainer Road? I'm a bit of a stander (que?) when climbing so reckon this is the reason it's a little bit higher when outside as inside I'm on rollers, frustrating though as I feel like I'm hammering myself even moar for a lower value!