Power has been restored to most households in Christchurch on Wednesday night, but about 15% of the city is without water or has very low pressure.
Lines company Orion says it has connected another 5000 homes on Wednesday.
About 150 customers who live near the red zone in central Christchurch are without power as workers have been unable to access underground cables to reconnect them.
Orion general manager Rob Jamieson says the supply in the eastern suburbs is likely to be fragile for some time and residents should be prepared for possible cuts.
Electrical faults have caused some fires.
Christchurch City Council says about 15% of residents have no water supply on Wednesday.
Water manager Mark Christison says crews are trying to build the pressure up in the pipes and continue repairs.
He says it will be another day before staff will have a better idea about the state of the waste water system.
The council says it could take six months to return to normal water supply.