Quick Answer: Powerline adapters put Ethernet frames onto the mains wiring, so a matched pair turns two wall sockets into a network link, but the socket itself never becomes an RJ45 port. A HomePlug AV2 1200 pair commonly moves 200 to 500 Mbps of real TCP traffic, adds about 2 to 10 ms of latency, and shares one collision domain with every adapter on the same distribution board. G.hn kits behave the same way with better rate adaptation. Treat powerline as a retrofit path, not as a replacement for Cat5e or Cat6 at 100 m.
Powerline is a bridge, not a wiring change. A modem chip injects a differential OFDM carrier between line and neutral, and the far adapter demodulates it back into 1000BASE-T frames. Nothing about the 120 V or 230 V circuit is altered and no Ethernet signalling ever reaches the socket contacts. Throughput and jitter depend entirely on how clean that carrier still looks at the far end.
What the Outlet Actually Carries
Mains wiring was never designed as a transmission line. Its impedance wanders with every appliance on the branch, unused runs act as stubs, and switch-mode supplies inject noise into the band the modem wants. HomePlug AV2 occupies roughly 2 to 86 MHz, while G.hn powerline profiles plan carriers up to 100 MHz. Both use adaptive bit loading, so a notch at 12 MHz costs carriers instead of killing the link.
How the adapter pair behaves
One unit bridges Ethernet to the mains, the second reverses it. They associate at power-up, exchange keys after a push-button pairing step, and encrypt payloads with 128-bit AES. Every frame is broadcast and heard by all paired adapters, so three adapters split one medium three ways.
What you need at each end
A modem adapter, a short patch cord, and a socket you are willing to dedicate. Where the run ends in a wall box, a power and Ethernet outlet keeps the RJ45 keystone and the mains receptacle on one plate instead of hanging an adapter off a cord.
Reading the Number on the Box
The figure on the carton is the PHY rate at ideal channel conditions. Usable TCP lands near 40 to 50 percent of it once contention and half-duplex turnaround are counted. The ranges below are field rules of thumb, not guaranteed values.
| Kit class | PHY rate | Typical TCP | Added latency | Port on the adapter |
|---|
| HomePlug AV 200 | 200 Mbps | 50 to 90 Mbps | 3 to 8 ms | 100BASE-TX |
| AV2 600 | 600 Mbps | 100 to 200 Mbps | 3 to 8 ms | Gigabit |
| AV2 1200 MIMO | 1200 Mbps | 200 to 500 Mbps | 2 to 10 ms | Gigabit |
| AV2 2000 MIMO | 2000 Mbps | 300 to 700 Mbps | 2 to 12 ms | Gigabit, sometimes 2.5G |
| G.hn 1200 | 1200 Mbps | 150 to 400 Mbps | 3 to 12 ms | Gigabit |
Note the port column: a 1200 Mbps adapter with a 100BASE-TX jack cannot exceed 94 Mbps of payload however clean the channel is.
Latency and the Shared Medium
An idle link adds a few milliseconds, which suits browsing and file copies. Under retransmission the penalty is not linear: a noisy branch forces repeated frames, and one-way delay can pass 50 ms with visible jitter. VoIP tolerates about 150 ms end to end, remote desktop notices 30 ms of jitter, gaming notices both. Because the medium is half-duplex and shared, two adapters transferring at once each get roughly half of what either managed alone.
When Powerline Beats Pulling Cable
In a rented flat with poured concrete walls or a ceiling full of fire stops, the alternative is often no link at all. A single in-wall Ethernet cable to one access point still beats four adapters, so run cable wherever a route exists and bridge only the hopeless span. Powerline cannot carry PoE, so cameras needing 48 V stay on copper. If the far end must feed two wired devices, settle the Ethernet splitter vs switch question first: a passive splitter is crossed pairs and gives two hosts no gigabit link, while a five-port switch behind the adapter does.
Practical Scenarios
- One room behind a concrete wall: use one AV2 1200 pair, expect 250 Mbps, and do not chain a second pair.
- Garden office on its own consumer unit: avoid powerline; the boards meet only at the meter, so fibre or buried Cat6 wins.
- Nightly NAS backup: avoid unless the job fits the window; sustained writes expose retransmission stalls a speed test hides.
- PoE camera at the far corner: avoid the adapter and use a local injector on a proper in-wall run.
FAQ
Does an Ethernet outlet need mains power to pass data?
Yes. The adapter is an active device that needs a live circuit at both ends to power its modem. A dead socket, a switched socket or a tripped breaker kills the link as surely as it kills a lamp. Move the adapter if the receptacle is controlled by a wall switch.
Can a powerline link cross the breaker panel or the other phase?
It crosses a breaker because the carrier couples through the busbar, but it loses 20 to 40 dB doing so. Crossing phases in a split-phase supply usually fails outright unless the signal is injected at the panel. That is why two sockets in one room work and two rooms on different legs do not.
Is powerline faster than WiFi in the same room?
Usually not. A 5 GHz or 6 GHz link at close range on a clear channel delivers more throughput and lower latency than an AV2 pair. Powerline wins through walls and floors, where WiFi falls back to a congested 2.4 GHz band or a weak mesh hop.
