It depends on the system level you buy. Each product will say the square footage on the box. For example, the 3 node system I bought can cover up to 4000-4500 sqft.
Other variables to think about is spacing between each node and what obstacles fall between them. The greater the distance between the nodes and the more walls/utilities/obstructions will decrease performance. For me, node one produces 214 Mbps. Node 2 is 50 feet away with a few walls and kitchen between it and I’ll get 80-100 mbps. Node 3 is upstairs about 30 feet away and I’ll pull 50-80 Mbps. Not bad for residential uses. Hopefully this helps.