I have a Garmin Vector Power meter (one-side) and I use plain Tac-X rollers with no technical bits on them. My speed and power come from sensors on the bike.
My power output seems low relative to my perceived effort compared to when riding on the road. I'm knackered between 200-300W and dying if I push towards 400W. On the road I am relatively comfortable at 200W and on a push I can go to 400W for say a short steep climb. When I slow down, I am still pretty tired spinning at 150W output on the rollers.
I don't doubt the accuracy of my power meter(or rather I don't doubt that the power meter works indoors as it does outdoors), so why does it feel so different?