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Changes have been made to power control systems after a peak in demand during a cold snap yesterday left some Otago households without warm water.
Aurora general manager operations and network performance Matt Settle said the issue affected customers in parts of Dunedin and Central Otago.
Yesterday was a period of very high demand, he said.
Many homes have hot water cylinders on a ripple control system, which allows the lines company to turn off customers’ hot water heaters during peak demand periods in the morning and evening.
In return, customers get a reduced rate for the electricity they consume.
The system functions to spread out periods of peak demand.
But yesterday the usual early afternoon drop in demand did not occur, and there was no room to recover the hot water heating load.
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.
Changes were made today to the ripple control system, to better account for scenarios where demand does not experience the normal drop between the morning and afternoon peaks.
The changes would reduce the amount of hot water load control undertaken in the future for similar demand profiles, Mr Settle said.
Leading Electrical Dunedin owner Ethan Kelly earlier said his company had received about four callouts due to the lack of hot water.
‘We had a few electricians going out and bypassing the ripple yesterday,’’ he said.
Last night’s fault was an uncommon one, he said.