Like roads, electricity networks experience periods of high demand where loading levels reach a peak and capacity is fully utilised.
Our peak loading in urban areas typically occurs on cold winter mornings when residential water heating load coincides with the start of the business day, and again on cold evenings when people arrive home from work and turn on their lights, heaters, and cook their evening meal.
As a contrast, because we have a substantial rural network the rural peak loads occur during summer months because of the high levels of irrigation pumps connected to our network.
One solution to cope with these periods of high loading is to expand the capacity of our network, and we are committed to an extensive capital replacement programme each year. In addition to this we believe, like all the other power utilities in New Zealand to promote other cheaper options, such as load management.
How we manage load
We operate a ripple signalling system that allows us to send signals through the electricity network to ripple receivers at customers’ premises. We provide a number of different signals to manage load in different ways:
- Our peak control signals are sent out only when they are needed - when load is peaking. Ripple receivers on peak channels switch off appliances (mainly hot water cylinders) to help reduce the peak. We start switching the peak channels back on as soon as load levels start to fall and we aim to keep the duration of control as short as possible to prevent any noticeable effects on customers' hot water supply
- Our fixed time control signals are sent out every day, turning appliances on (mainly hot water cylinders and night store heaters) at times when our loading levels are always low. This “fixed time control” permanently shifts load away from the day time periods when peaks occur.
Most consumers install ripple receivers to take advantage of the cheaper pricing plans that are available. An additional fixed charge is applied for electric water heating, where a ripple receiver is not installed.