A powerline networking kit (containing two adapters, each with an Ethernet port and an electrical plug) helps you extend your home network to far reaches of your house. They use your existing electrical wiring. Powerline networking is useful for places where Wi-Fi can't reach, and ethernet is an impractical option. For example, you far off garage, or a multistorey complex. Remember, powerline is not for short space where Wi-Fi would do.

Good powerline adapters give data speeds pf 100 Mbps+ , similar speeds that wireless routers provide, necessary for your HD video streaming, game streaming from your PC to your TV, or other daat intensive needs.

The thing to remember about powerline networking is that bad power connections, more number of circuit breakers along the route, hinder the signal quality.

The best powerline networking kit / adapter: ZyXEL 1200 Mbps Powerline AV1200 Gigabit Adapter, Starter Kit - 2 Units (PLA5405KIT) (HD video streaming capability)

The second best powerline networking kit / adapter:  Netgear Powerline 1200 + Extra Outlet (PLP1200-100PAS) - The fastest powerline adapter