A large vehicle must have been used in a substation cable theft which caused £30,000 of damage, Nottinghamshire police have said.
Offenders stole £1,000 of copper piping from Pintail Close in Netherfield, between 18:00 GMT on 18 November and 08:00 GMT the next morning.
The theft led to power being switched off in hundreds of homes and businesses in the area.
About 100 litres of mineral oil was also drained into a nearby watercourse.
The thieves shut down the circuit board before stealing three copper coils from the transformer and then cut the 11,000-volt switch cable, Nottinghamshire Police said.
During the theft the oil was drained from the transformer, causing harm to the local environment and wildlife.
Det Sgt Rob Lloyd said: "This offence has had major repercussions for the local area.
"The offenders were clearly a highly-skilled and equipped team, who would have required heavy lifting equipment to lug a ton of copper coils away from the scene."
Anyone who witnessed the theft or saw anything suspicious in the Victoria Park area of Netherfield should contact Nottinghamshire Police.