Down the road from me is a street with LED lamps that were fitted around 2008, and, due to the usual competence of the council electrician contractors, they all have shorting caps, and the group relay was disconnected, and each was wired to the phase wiring of the overhead line. Now on 27/7/365 they are still sort of functional, as in they still emit some light at night, even though more than half the dies in the head are failed, and these obviously have failed led detection in the optical head, and a really good power supply. Lumen output is down by more than half, they used to be impossible to look at during the day, but now they are a lot dimmer.
The other ones in the street had to be replaced within a year, as they all failed, so the supplier, Beka, replaced them, and then the metro also put in a lot more additional fixtures to supplement the light, replacing the 400W HPS fixtures with an 80W fixture on the street side, and an 18W fixture on the pavement side.
Still a few 400W HPS and MH units left though, and the rear alley by me got a relamp with a new 80W MV fixture, as the ballast had rotted away. I kind of wanted that old Phillips lamp, but it fell to pieces when they touched it, so in went a Beka GRP fixture, complete with 80W Osram lamp. I did get the old shorting plug though, to use on my other 80W fixture instead of the photocontrol.
Typically the LED is between 80W and 135W, replacing a 400W fixture, and for residential 18W or 36W, you place either one lamp assembly in, or two, and set the power supply accordingly.