Power stations on the roof

- Using solar energy makes more sense today than ever, say its proponents. So why don't more New Zealand homes have it?

As the sun blazes down and temperatures soar to record highs, hot summer conditions are drying out Canterbury, yet free solar energy is going to waste.

Instead, higher power charges seem likely and more power stations are planned to combat long-term power shortages.

Thousands of homes are being built in new subdivisions, yet few if any have solar water heating or alternative energy systems.

"Each solar water-heating unit is a power station on the roof, creating power exactly when the sun is drying out the hydro lakes," says Auckland-based solar energy advocate Bob Riley, of Reid Technology, who imports Australian-made solar hot-water systems.

New Zealand is lagging behind in its take-up of solar technology, he says. Here, less than 1 per cent of households use solar-heated water.

This compares with 3 per cent in the United States and more than 10 per cent in Australia, where it is mandatory in some areas.

In 2005, both Victoria and South Australia will make it mandatory for new homes to incorporate solar water heating. It is already mandatory in Greece, Israel, and Japan.

"We should do the same. If we were to bring that in, it would resolve (a potential energy crisis). The international trend is to solar hot water, saving money, energy and global emissions, and preventing more power stations and cables."

Throughout Greece and Turkey, centuries-old houses in remote villages now have solar water- heating units on the roof.

For villagers, and hotel guests, fed up with sporadic hot-water supplies, the constant supply of free hot water is a boon. It also reduces power bills dramatically.

Eventually, perhaps after only a few years, solar water heating pays for itself in reduced power bills.

"Solar hot water can cut annual family power bills and demand by up to 50 per cent, thereby leaving more power to go around and defer the building of new generating plants," says Riley.

He is not alone. David Bryce, whose Port Hills eco-subdivision is ready to go (E6), says his home has had solar water heating for 15 years and "it hasn't missed a beat".

It has been mistakenly seen, however, as "fringe technology". Now, with power prices certain to rise, more people are recognising the benefits of solar water heating.

Another advocate of solar energy is University of Canterbury emeritus professor of engineering, Arthur Williamson, who launched solar water-heating company Thermocell.

He stops short of urging solar water heating to be made compulsory. It is energy efficiency, by whatever method, that needs to be encouraged, he says.

Most all-electric houses use 40 per cent of their power (about 4000kWh per year) to provide hot water. A solar system will provide about 50 to 75 per cent of the hot- water energy depending on the amount and management.

"By my calculations a typical domestic solar water heater is the equivalent of about 600W of hydro. So if every house in New Zealand had one, it would be more than one Aqua equivalent," he says.

"The next question is how fast could we do this? I reckon about 20 to 40 years."

Solar water heating saves homeowners money, and the savings increase in tandem with rises in electricity prices.

Using solar energy also reduces greenhouse gas emissions by about two tonnes of carbon dioxide a year for each domestic hot-water system, says Williamson.

"Solar water heating is a technology which is available and implementable now. It is in fact underutilised."

John Veix, organiser of this year's Christchurch Sustainability Expo uses photovoltaic panels and a wind turbine at his own home to produce power. Although his company, Solar Electric Specialists, specialises in photovoltaic systems, small wind systems, and ultra- energy- efficient appliances, and does not sell solar water-heating units, he says solar water heating is a logical first step.

"I have always been a great advocate and proponent of solar water- heating systems, having personally had them for about 20 years, and am the first to say that solar water heating is the first thing that people should do to save money on their power bill."

Pros and cons

* Pros: A solar water-heating system will save money in the long- term, eventually paying for itself through lower power bills, and it is good for the environment.

* Cons: The initial outlay is high, with an average solar water system costing about $3500 to install.

* Points to consider: Opt for a thermosyphon system (with a tank on top of the collector), or a pumped system with separate hot- water cylinder. Place in the sunniest spot with the collector panels at a 45deg tilt (to match the latitude.)

* Cost analysis: $3500 outlay, $360 savings a year (saving 3000kW at 12c a kW/hr on the hot-water component of an average household's annual 10,000kW electricity use).