Water heating cuts save plenty of power says department

Taupo Times, Volume 23, Issue 52, 2 July 1974, Page 7

Water heating cuts save plenty of power says department

Taupo families are having to bear 15-hour, water heating cuts These cuts are more drastic than in most centres. In this article, the New Zealand Electricity Department explains its viewpoint on the need for the cuts.

With most New Zealand homes receiving water heating cuts, it is important that householders realise this measure saves plenty -of electricity. Most hot water systems in this country are designed to handle cuts all the time, not just during electricity shortages. The reason for this is historical. With a basically hydro generation system evolving, it was in the national interest to electrically heat water off-peak (when demand was not high). This had the beneficial effect of keeping peak demand down, lessening the day-to-day burden on ~generating resources by keeping morning and evenirig peaks in electricity use *within reasonable bounds. (Electricity peak demand times vary but generally ccMncide with people starting the day off or arriving home from work and

switching electrical appliances on.) The net result is that almost all hot water systems in this country are remotely controlled. This allows electrical supply authorities to switch off hot water systems during times of maximum electricity demand by sending a signal over the reticulation system which operates a relay in each home. Controlled water heating has a threefold effect; it reduces charges to the supply authority, hence to the consumer and lowers the amount of generating capacity required. In New Zealand, electricity demand peaks tend to be of short duration. Thus, under normal circumstances, water heaters could be on as much as 20 hours a day. If peak load was the only form of control, the water in most cylinders would

come to boiling point and continue to boil until some hot water was used. This would be extremely wasteful, so all cylinders are required by regulation to be fitted with a stat.Thermostatically - controlled hot water cylinders ensure the system turns off once the water reaches the required temperature. As a result, a hot water system switches on and off several times each day, depending on the amount of hot water used. About 92 per cent of New Zealand homes have

electric water heating, a high proportion by world standards. These are basically storage systems, holding 30 gallons or more, heated by an element. Cylinders are lagged and this form of insulation keeps the heat in. Storage systems allow a consumer to use a lot of hot water before the effects of an electricity cut are noticed. Their capacity is normally enough to override the time a system is off during demand peaks or electricity cuts. Because hot water sys-

tems are governed by New Zealand Standards, they are designed for storing hot water heated off peak to a thermostatically - controlled temperature. This gives the consumer efficient water heating when electricity supplies ( are normal but also belps when electricity is short — as at present. Peak load control systems allow supply authorities to conserve on water heating which normally consumes over a fifth of all electricity generated in this country. By lowering the standard of hot water service, an authority can make appreciable electricity savings. The reduction in the amount of hot water available varies from week to week and from supply authority to supply authority. But basically, each household in the country is still getting at least one

cylinder full of hot water a day. Providing the householder does not expect to do all the washing and family bathing in one day, he or she should be able to get by with minimum inconvenience. If the compulsory saving was made on other forms of electricity use, such as heating or lighting, the inconvenience would be far greater because only one method could be employed; total or blanket cuts. Thus restrictions on supply to hot water systems are one of the most important ways supply authorities can conserve electrical energy. This is contrary to some public opinion which holds that electricity savings from reduced hot water services are minimal. But savings are being made, and made in units. Information compiled by the supply authorities confirms this. Consumers are using less hot water, conserving what they have. They are also tending to use cooler water where once they would have used hot. One of the main arguments against hot water cuts is that more electricity has to be used to heat the water up again. This can be nullified by using a specific example. If a consumer uses 40 gallons of hot water in normal times, the replacement 40 gallons is reheated as the hot water is used. Nevertheless, 40 gallons of cold water must be raised to thermostat temperature. However, when the power is switched off, the 40 gallons of hot water used up then remains a 40 gallon tank of cold water. When electricity supply is restored that 40 gallons has

to be raised to thermostat temperature. Thus, in both cases, the same amount of electricity is used. Greater savings can be made with cuts long enough to ensure all cylinders run cold. In this way the amount of hot water used and thus the amount of electricity used is . limited, giving considerable savings. Alternatively, frequent cuts of short duration could be made and this would ensure the water in the tank never reached thermostat temperature. With long cuts the consumer would get a tank full of really hot water. With frequent short cuts the water would be luke warm but available for a longer period. The final common misconception surrounding water heating cuts is that they result in the consumer paying more. This is far from the truth. A consumef's meter measures energy; if he used less he pays for less. If a consumer finds his electricity bill is up, he should stop and reflect. With the onset of winter he is probably using more heating, having more hot baths and putting more appliances to greater use. And if he thinks water heating is costing him more, he should stop and think once again. In winter, water can enter your house 25 deg. F colder than in summer. This means morg electricity is required to bring it up to the cylinder's thermostat setting. And finally, remember winter is when the consumer wants his hot water really hot. In summer it can merely be a case of giving a little heat to cold water.