Cwm Dyli is the location of a hydro-electric power station on the southern flank of the Snowdon range in North Wales.

The railway was planned to run through the same valley as the power station and be fed with an electrical feeder, but the enterprise ran short of funds and the attempt was abandoned.

Cwm Dyli was claimed to be the largest electricity generating plant of its kind in Great Britain at the time.

[3] Electricity produced here was also used to power the Carnarvon Long Wave Wireless Telegraph transmitting station built by Marconi in 1913–14 near Waunfawr.

Water for the site primarily comes from Llyn Llydaw, some 320 metres above the power station, where rainfall is very high.