the speed of powerline depends on the electrical work in the house. if you live in a new house, you'll be fine. if you live in an older house, you'll probably get lousy speeds.
These powerline adapters are rated at 500 Mbps. It's important to note that on many older homes, you're likely to get ~100 Mbps (more than enough for most users), depending on the distance the signal has to travel. I lived in a townhouse that was 40 years old and I could barely get a decent signal with Wifi. These powerline adapters solved that issue and they solved it well.