Where's your numbers for that? My local muni operates about 10,000 street lights. If HPS averages 400W apiece, that's 4 megawatts, run for maybe 10 hours a day,

Where's your numbers for that? My local muni operates about 10,000 street lights. If HPS averages 400W apiece, that's 4 megawatts, run for maybe 10 hours a day, at $0.10/kWh that's $4,000 a night... Now if by "years" you meant "two years", then fine, I can believe it- but two years is still a fantastic payoff period. Don't forget HPS burns out pretty regularly too. Tactic my muni is using is simply to replace burnt-out HPS with LED instead of repairing it. Lo, after a few years we're probably half LED.