Chilly capital sets power demand record

It was Wellington's turn to break the record for power demand last night as city-dwellers returned home in freezing southerlies and began turning on the heating.

"So far that's the feature for Thursday," said Chris Roberts, spokesman for national electricity grid controller Transpower, which has been juggling huge demand for power as the country remains in the grip of icy weather.

Power demand surged to a peak of 630MW in Wellington at 5.30pm when the temperature was a brisk 6C. The previous record was 605MW.

Once again, power companies were using the "ripple control" hotwater control to turn off household cylinders to try to spread peak demand.

After several days of lukewarm showers, some Herald readers have questioned whether turning off hotwater cylinders ends up costing consumers money, as the cooler water in the cylinder has to heat up again - using more power.

According to lines company Vector, Auckland's main electricity supplier, the answer is no.

Because customers on the ripple control system pay a lower tariff, the practice does not add to power bills.

David Russell of the Consumers Institute said that was probably correct although to know whether an individual household was paying more because the hot water was being turned off you would need to know how well the cylinder was insulated and for how long it was switched off.

Energy Efficiency and Conservation Authority spokeswoman Vicki Connor said the system was about managing peak demand.