The council claims the scheme will save £100,000 and nearly 600 tons of carbon dioxide emissions every year.
But the Government-backed blackouts have provoked anger from police leaders and motoring organisations.
Derek Barnett, of the Police Superintendents' Association, said: "Good street lighting reduces crime, it makes the public feel safe and it reduces the risk of road traffic accidents.
"I would need to feel confident that the environmental savings were being balanced against the impact on local crime."
The latest move is the most draconian rationing of street lighting since the power cuts of the 1970s.
(Thanks to Nick for the heads-up.)