Line companies would need to have a lot of control over the charging of electric vehicles, she said. "Imagine if people drove home from work, plugged their cars in about 6pm and they all started drawing power. Charging the new electric car Mitsubishi will be something like a clothes dryer on full blast for seven hours."
Charge times would need to be staggered through the night, Wright said. Seven hours was a slow charge and rapid charges being developed overseas demanded about 7 kilowatts of power. "This is about the same as the current peak demand of an average house."
A recent study found that if all the cars in the United Kingdom were replaced by electric vehicles tomorrow, electricity use would only rise by 20 per cent but peak demand would rise by 400 per cent. Wright said electricity retailers needed to ensure smart metres being rolled out across the country were able to be linked into a home area network that connects the household devices using energy.
That would enable real-time information on electricity prices which would help as suppliers moved towards time-of-use pricing systems. A recent survey of Mercury Energy pricing in Christchurch found electricity cost 39 cents during peak time from Monday to Friday but just 9 cents at nights and weekends. It would also facilitate the introduction of smart appliances, such as a smart refrigerator which would know to defrost itself at night when electricity was the cheapest, she said.