Solar Water Heating Case Studies
From north to south, solar water heating is giving New Zealand households a good supply of hot water at reduced cost.
Many homeowners and home business owners report significant benefits year-round.
Rod and Christine - Kerikeri
Rod and Christine Brown run the Summerhouse bed and breakfast in Kerikeri. This is Greenglobe certified, which means that it is built and operated on energy conservation principles. It includes a solar water heater which has been operating for seven years.
“I am extremely satisfied with my solar water system, which is a Solahart 300-litre, 302L,” says Rod. The system has two panels mounted on the roof, facing north.
Rod has carefully monitored their solar water heating system and can give accurate figures. He says that electrical water heating is only 13% of their annual power bill (compared to about 30% for the national average).
A timer is set to switch on an electrical booster for one hour just before 7am, to make sure the water is at 60?C. This is done summer and winter.
In summer they may have six or eight people wanting showers at the same time in the morning, which really drains the hot water. In winter there are fewer guests, but the available solar energy is less.
There is also a temperature readout and a manual switch for the booster on the kitchen wall. Rod keeps an eye on the temperature and switches the booster on at any time he thinks it’s necessary.
“I am always astonished with a widely held belief that solar power is not economic,” says Rod.
He points out that a seven year payback means an 11% return on investment, tax free, and says that his electricity tariff went up an average of 9.7% per annum for five years. He also believes that solar water heating is in the national interest.
Joy - Devonport, North Shore
Joy runs a bed and breakfast with her husband in Devonport, Auckland. She has an Edwards solar water heater which was installed 10 years ago when the house was built.
The panels face north and are set into the roof which is pitched at 45? - slightly steeper than the ideal angle.
The system has a 180-litre cylinder in the roof space, with an electric booster which is turned off most of the time. There are no controls or monitoring displays although Joy says a temperature gauge would be useful.
Solar hot water is used in the dishwasher and washing machine (set at 40?C) as well as sink and bathroom. The B&B has guests mostly in summer, and sometimes there is a lot of bedding and towels to wash. Sometimes guests use a lot of hot water, which means the booster must be turned on.
Joy says: “I think it [solar water heating] is fantastic and would thoroughly recommend it.”
Adam - Napier
Adam owned a 1900s house on the hill in Napier.
Its roof faced north and tilted 35? - just the right angle. He installed a Beasley 330-litre solar water heating system in 2002.
The unit cost him $3900 including installation costs.
Adam reports that he switched the electric booster off most of the time, and temperatures in the cylinder often reached 75?C.
There were normally two people living in the house. Occasionally, when guests stayed for a while, the electric booster had to be switched on.
Adam describes this system as “brilliant”, and says that the key is to get a huge storage cylinder. He even topped up the swimming pool with it occasionally.
He points out that many roofs in Queensland have a solar water heater and thinks the New Zealand government should do more to encourage solar water heating here.
Adam has since moved to Auckland, and is installing another solar water heating system in his present home.
Jeanette - Lower Hutt
Jeanette and her husband installed a Chromagen solar water heater in their home in Lower Hutt in April 2006.
This has a 200-litre cylinder and two solar panels facing north and tilted at about 41?. The system uses a glycol mixture to prevent frost damage.
There is a controller which displays temperatures at the top and bottom of the cylinder. The electric booster heats only the top quarter of the cylinder. Jeanette says installing this system in their house was no problem.
In June 2006, after two months of a cold winter, Jeanette is “really surprised at the amount of heating [they] are getting even though many days appear sunless”.
When the sun does shine, the lower thermometer shows temperatures of around 43?C which means that the electric booster only has to supply around half the heat. It is timed to switch on at 5am and only heats if the temperature is too low.
Raymond - Oxford, Canterbury
Raymond lives with his family in Oxford, Canterbury, in a large, old house.
He has a Solahart water heater with three panels, installed in 2003. This heats the water to boiling on sunny days.
The system is also connected to a woodstove and a diesel boiler. These also heat the house in winter with water circulating through a system of seven radiators.
Raymond does not use electricity for water heating at all, and says he is very happy with his system.
Lesley - Dunedin
Using the warmth of the sun to heat their water has slashed a Dunedin family's power bills by a third.
Lesley and her family of four have reported that their power bills have been about a third lower since the installation of a solar water heating system at Easter, 2005.
The household relies totally on solar power for water heating in the summer months. In cooler months, they use an electricity booster system for an hour a day. They found that even in last year's cold month of June, the temperature of the water on sunny days could get up to 60 degrees Celsius.
Installation of the solar water heater was "no hassle at all", says Lesley. "It has worked really well for us with ample hot water and lower power bills. If everyone building a new house had to have solar installed it would take some pressure off the national grid."
Steve - Geraldine, South Canterbury
Steve lives in Geraldine, near Timaru. His household has two adults and three children.
He has a Thermocell solar water heater with a 360-litre cylinder and an electrical booster. There is a heat exchanger system which avoids problems with freezing, and a pump to circulate the water. There is also a woodburner and wetback for use in winter.
The house faces 20? west of north. This lets the winter sun into one end of the house in the morning, and all the other rooms for the rest of the day. The solar panels were recessed into the roof when the house was built, so they also face 20? west of north.
If the roof angle had been the ideal 44?, Steve would have used six panels, but because the roof slope is only 18? he decided to add two more.
Steve says that the solar water heater “works brilliantly in summer”, needs some boosting in spring and autumn, and provides some preheating in winter.
There is a display panel that shows the water temperature, and Steve controls the electric booster manually. He says that it’s essential to control the booster or you get too much hot water and a larger than necessary power bill.
He thinks a timer would be a good idea if people don’t want to control the booster manually.
Steve runs the dishwasher off the hot tap to minimise the dishwasher cycle time, and to use solar (or wetback) heat.
He offers some tips:
- make best use of solar heat by using hot water during the day if possible.
- if the cylinder is large, the electrical booster can be used on night rate only, which saves more money.
More information
From Smarter Homes
From consumer.org.nz
Note: you may need to be a subscriber to access some of this information.
From other sites
For more information the best place to start is the Energy Efficiency and Conservation Authority's Solarsmarter solar water heating website. You can also find out more from the websites of the New Zealand Solar Industries Association. The Energywise website has information about water heating options.
The ZALEH database on BRANZ’s website gives information on several houses built using energy efficient ideas. Several have solar water heating and show good savings on power bills.
