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Changes have been made to power control systems after a peak in demand during a cold snap yesterday left many Otago households without hot water.
Dunedin residents, from across the city, took to local social media on Monday night to say they were without hot water.
Some said the problems started on Friday evening, leaving them cold over the weekend.
Aurora operations and network performance general manager Matt Settle said the issue affected customers in parts of Dunedin and Central Otago.
Monday was a period of very high demand, he said.
Many homes had hot water cylinders on a ripple control system, which allowed the lines company to turn off customers’ hot water heaters during peak demand periods in the morning and evening.
In return, customers got a reduced rate for the electricity they consumed.
The system aimed to spread out periods of peak demand.
But on Monday the usual early-afternoon drop in demand did not occur, and there was no room to recover the hot water heating load, Mr Settle said.
It was likely that customers who used most of their hot water would have run cold, but customers who used a low or moderate amount of the hot water from their cylinder would not have noticed any difference to their water temperature, he said.
Changes were made yesterday to the ripple control system, to better account for scenarios where demand did not experience the normal drop between the morning and afternoon peaks.
The changes would reduce the chance of the same thing happening to customers again, Mr Settle said.
Leading Electrical Dunedin owner Ethan Kelly earlier said his company had received several callouts due to the lack of hot water.
‘‘We had a few electricians going out and bypassing the ripple yesterday,’’ Mr Kelly said.
The bypass meant hot water cylinders ran from standard power circuits rather than the ripple relay.
Monday night’s fault was an uncommon one and Aurora had done a good job of getting everything up and running, Mr Kelly said.