Water heating uses approximately 29% (source: BRANZ) of the total energy use in an average home
Websites with information on water heater systems and efficient use of hot water are:

Energy Wise http://www.energywise.org.nz/yourhome/hotwater/
Level http://www.level.org.nz/energy/water-heating/
Smarter Homes : http://www.smarterhomes.org.nz/energy/water-heating/

There are many options for domestic hot water heating. Most common are:

• Electric storage water cylinder
• Hot Water Cylinder Wrap
• Gas storage water cylinder
• Gas Instant water heater
• Electric Instant water heater
• Solar water heater
• Heat pump water heater

Storage water cylinders are the most common form of water heating in New Zealand, with about 95% (source: BRANZ) of homes using this system.

Electric Storage Water Cylinder:#top

An electric storage water cylinder is one of the cheapest water heating methods to install, which is why these are so popular. As they store hot water, the electric element can be turned off for several hours by electricity companies to manage their load, allowing electric water heaters a slightly cheaper electricity rate than light and power in your home.

Many sizes are available depending on the situation and the likely demand on hot water. Homes with more occupants require a larger cylinder to ensure an adequate supply of hot water is available as the electric heating element cannot heat the water is quickly as it is used.

These cylinders also come with different pressure ratings, referring to the water pressure. Most new homes use mains pressure, being the water pressure available from the street. With mains pressure water heating systems, the water pressure in both the cold and hot taps will be the same.

Older systems or systems with a wetback heater or wetback booster generally use a lower pressure, and extra pressure reducing valve is required (commonly called an Apex valve) to reduce the water pressure before it enters the cylinder. Tapware and shower heads also have to be suitable for lower (both cold and hot water at low pressure) or unequal (mains pressure cold and low pressure hot water) pressure systems.

All new electric storage water heater cylinders must be A-grade cylinders. This means that they have the highest insulation value currently available. Existing homes may have B-grade cylinders, or no grading at all, these installations would benefit from a hot water cylinder wrap, please refer to the hot water cylinder wrap page by clicking here (link to cylinder wrap page). Cylinder wraps can only be used on electric storage water cylinders.

Storage Cylinders have heat being lost from the cylinders constantly known as standing losses. The fact that they feel warm means heat is escaping. Insulation helps keep the heat inside, which is why older cylinders benefit from installing cylinder wraps to improve the level of insulation the cylinder.

Some electric storage water heaters are fitted with extra pipes to enable these to be connected to a wood fire with a wetback water heater or wetback booster. All wood fires have to meet emission and efficiency regulations. Please refer to the wood fire page for more information. (make clickable link)

Sample of a wetback coil inside a wood fire ( www.firenzo.co.nz )

Gas Storage Water Cylinder:#top

These are similar to electric storage water heaters however they use natural gas to heat the water. Both indoor and outdoor models are available, therefore if there is no space inside the house, the water heater can be located outside.

Instead of an electric element, gas water heaters have a gas burner at the bottom of the cylinder, and a flue that runs through the middle. A gas storage heater will reheat a cold water heater much quicker as the heating capacity of the gas burner is typically three to four times the heating capacity from an electric element.

If gas water heaters are inside the house, a flue for the exhaust gas and a vent for fresh air are required.
Gas water heaters are recommended to be serviced annually.

Indoor Gas Storage Water Cylinder

Outdoor Gas Storage Water Cylinder

Gas Instant Water Heaters:#top

As the name suggests these water heaters only heat as the hot water is required, there is no storage cylinder, and provided there is water and gas, it will keep supplying as much hot water as is required.

Because there is no storage, there are no standing losses, making these water heaters more efficient than storage water heaters. New high efficiency water heaters are reaching 95% efficiency (source: Rinnai) by using a second heat exchanger to preheat the incoming cold water with the exhaust gases.

These water heaters can run on either piped natural gas (if available in your street) or bottled LPG.
Several sizes are available depending on the hot water demand, and different options allow installation inside (with flue and venting) or on the wall outside thereby not taking up any space inside the house. Boxes and lids are available to hide the water heater out of sight if desired.

Electric Instant Water Heaters #top

These are also available, designed for low use operation. The electric element is quite large therefore requiring large cable sizes and has to be connected to peak electricity to ensure operation at all times.

All electric and gas water heaters are available from your local plumbing supplier and building supply stores.

Solar Water Heating #top

With increasing costs of energy and improvements in design and technology of solar water heating systems, using the sun for water heating is becoming more popular.

A solar water heating system for your home will typically cost between $4,000 and $8,000 (source Consumer Magazine), with a typical payback of around 10 years, depending on the system selected, installation costs and hot water use.

There is enough solar radiation from the sun in Rotorua to make solar hot water feasible; a map produced by NIWA (www.niwa.cri.nz) shows the average sunshine hours is between 1,800 and 2,000 per year.

NZ Average Sunshine Hours

The average level of daily solar radiation in Rotorua is 3.93kWh/m2, with higher levels recorded during December and January and the lower in June and July. The table below shows the average daily solar radiation for each month.

During summer solar water heating should be capable of producing enough water for your home with occasional boosting from electricity or gas possibly required on colder days. During winter the solar water heater could supply over 30% of your hot water demand, with the remaining 70% being heated by other means such as electricity or gas or maybe a wetback heater.

The Consumer Institute together with EECA have produced a solar water heating guide with is available here clickable download link (1.1MB to download)Solar Water Heating Guide

There are many different solar water heating systems available, with new systems being introduced all the time. A recent introduction into New Zealand is a closed loop drainback system, eliminating the need to use energy or chemicals to prevent the panels from freezing or overheating. Information on how this works is available by clicking here: Drainback System

Evacuated tube solar collector

Glazed flat panel solar collectors

Glazed flat panel solar collectors with roof mounted cylinder

Financial Assistance

You may be able to obtain financial assistance from the Government when you install an approved solar water heater. More details on systems and suppliers are available from the Energywise website: : http://solar.energywise.govt.nz/consumers/financial-assistance

Rotorua Suppliers and Installers of solar water heating systems (in alphabetical order):
• Gas & Solar Ltd * link http://www.solartech.co.nz/
• GB Teat Ltd *link http://www.heatingpartners.com/solar.htm
• G Brooks Plumbing *link http://www.solarhotwater.co.nz/
• Beta Electrical * link: http://www.solarpeak.com/

If you are a supplier or installer of solar water heating systems in the Rotorua area and you are not listed here, please e-mail us your details for consideration: info@energychampion.co.nz

Links to manufacturer or supplier’s websites (in alphabetical order):

• Azzuro Solar http://www.azzurosolar.co.nz/
• Eco Solar http://www.ecosolar.co.nz/
• Ewa-Tec Ltd www.ewa-tec.com
• Reid Technology http://www.reidtechnology.co.nz/
• Solahart http://www.maintenance.co.nz/
• Sola 60 http://www.sola60.co.nz/index.htm
• Sunz http://www.sunz.co.nz/
• Switch Energy http://switchenergy.co.nz/index.cfm/1,64,0,42,html/Solar-Collectors

Websites that contain useful information:

Solar Industries Association: http://www.solarindustries.org.nz/
Level (BRANZ) http://www.level.org.nz/energy/water-heating/solar-water-heating-key-principles/
Smarter Homes http://www.smarterhomes.org.nz/energy/solar-water-heating/
EcoBob * link http://www.ecobob.co.nz/EcoArticle/1069/105/Water-Heating.aspx

Hot Water Heat Pumps #top

Most homeowners who have heat pumps use them to heat and cool their homes. But a heat pump also can be used to heat water – either as stand-alone water heating system, or as combination water heating and space conditioning system.

How They Work:

Hot Water Heat Pumps (also known as heat pump water heaters) use electricity to move heat from one place to another instead of generating heat directly in a similar way as a heat pump heats air. They can be two to three times more energy efficient than conventional electric resistance water heaters. To move the heat, heat pumps work like a refrigerator in reverse.

While a refrigerator moves heat from inside the refrigerator and expels it into the surrounding room, a stand-alone air-source hot water heat pump pulls heat from the surrounding air and transfers it at a higher temperature into a tank to heat hot water.

You can purchase a stand-alone hot water heat pump system as an integrated unit with a built-in water storage tank and back-up resistance heating elements. You can also retrofit a heat pump to work with an existing conventional storage water heater.

Hot Water Heat Pumps require installation in locations that remain in the -10ºC to 40ºC range year-round and provide at least 120 cubic meters of air space around the water heater. Most are designed to be located outside to ensure an ample supply of air.

Cool exhaust air can be ducted to a room or discharged into the outdoors. Hot Water Heat Pumps will not operate efficiently in a cold space. They tend to cool the spaces they are in.

Diagram of a Hot Water Heat Pump

Ambient air is fan forced over an evaporator where it gives up some of its heat. This heat warms the gas which is compressed by a compressor into a hot gas. This hot gas is passed through a heat exchanger to heat the water inside the cylinder. During this process, the hot gas turns into a warm liquid. In the expansion valve this warm liquid turns into a cold gas again, ready to start the process again.

If you are a supplier or installer of heat pump water heating systems in the Rotorua area and you are not listed here, please e-mail us your details for consideration: info@energychampion.co.nz (make link that opens e-mail message??)

Links to manufacturer or supplier’s websites (in alphabetical order):

Econergy Ltd http://www.econergy.co.nz
Efficient Heating NZ Ltd http://www.efficientheating.co.nz/productbrochure.html
Hot Water Heat Pumps Ltd http://www.waterheating.co.nz/domestic_hot_water.aspx
Quantum Energy Ltd http://www.eco.co.nz/products/quantum.php