Choosing A Hot Water System – all you need to know

A GUIDE TO CHOOSING A HOT WATER SYSTEM

Choose a gas hot water system with at least a 5-star energy efficiency rating to save 15% on running costs
A gas-boosted solar hot water system will double those savings and you may also be eligible for a Victorian Government rebate: up to $1,500 for Melbourne households and $1,600 for households in regional Victoria
Use the energy rating label to find the most efficient appliances. The more stars the better. Every extra star can save you hundreds of dollars each year

IMPORTANT CONSIDERATIONS

• Install the system close to your hot water outlets so water doesn’t have to travel far and lose heat along the way
• Insulate the first few metres of piping to reduce heat loss around your hot water system
• When installing hot water systems in frost prone areas, check the system has frost protection and that this is covered in the warranty
• Buy a gas boosted solar or a gas hot water system with at least 5 stars. Choose the right size system for your hot water needs
• Choose electric ignition instead of continuous pilot light to reduce gas consumption
• Keep your shower under minutes and you will save $50 each year
• Carefully read warranty details
• Make sure your roof’s structural strength is assessed (by the installer) to ensure it can support the weight of a solar system
• Solar systems cannot be shaded by trees or nearby buildings
• Storage tank and solar collectors (the solar panels) should be as close together as possible to reduce the length of the connecting pipes
• Ensure some form of frost protection is included
• All plumbing must be carried out by a licensed plumber. The plumber will issue a certificate of compliance
• All electrical work for the installation of electrical heating elements and electric pumps must be carried out by a registered electrical contractor. The contractor will issue a certificate of electrical safety
• If your water quality is poor, then you need to be aware that the system’s warranty may be affected

TIPS FOR BETTER PERFORMANCE

The most effective way to obtain maximum performance from your solar hot water system is to make efficient use of hot water in your home. Things you can do include:

• When possible, do jobs requiring hot water early in the day. This allows the water remaining in the tank to be reheated by the sun and reduces the auxiliary heating period
• Keep the booster thermostat at its recommended setting of 60deg C. Remember the lower the thermostat setting the less energy used to supplement solar heating
• Install your system as close as possible to the kitchen, bathroom and laundry, which are the main hot water draw-off points around the home. If this is not possible, install it close to the kitchen
• Conserve hot water by using it efficiently
• Fit a low flow shower head. Showering accounts for over 30% of hot water usage in the home. This can be dramatically reduced by fitting a low flow shower head or a flow restrictor to an existing showerhead.
• Follow the manufacturer’s recommendations for the maintenance of your solar hot water system

ABOUT SOLAR HOT WATER SYSTEMS

Solar hot water systems use the suns energy to heat water in much the same way as water in a hose left on the lawn gets hot on a sunny day.
Using the suns energy to heat water can reduce your household hot water bills by more than 60% each year.
Solar hot water systems also help conserve our natural resources and the environment, and reduce greenhouse gas emissions.
Solar water heaters are generally equipped with gas or electric boosters to ensure that you are never without hot water.

WHAT SYSTEMS ARE AVAILABLE

STORAGE WATER HEATERS

Water is heated and stored in an insulated tank ready for use throughout the day. They operate most economically on solar energy, natural gas or off-peak electricity. They can also run on LPG, peak electricity or solid fuels such as wood or briquettes.
They are available as either:
A – mains pressure: hot water is delivered at a similar pressure and flow rate as the cold water. This means that more than one outlet can be turned on without affecting supply pressure. Normally located at ground level, and can be installed either inside or outside the home
B – Constant pressure: hot water is delivered at lower pressure than mains pressure units. They are normally located in the roof space of a home, and the pressure depends on the vertical distance between the tank and the point of use. Constant pressure units are often cheaper to purchase and have much longer life expectancies than mains pressure systems. Correctly plumbed, they will provide satisfactory service. They are also known as ‘gravity feed’ or ‘low pressure’ systems.

CONTINUOUS FLOW (instantaneous) water heaters

Water is heated only when required and therefore does not required a storage tank. As water is heated instantaneously, they cannot ‘run out’ of hot water
They are generally smaller in size than storage systems and can be installed internally in a cupboard (gas units must have a flue) or externally on a wall
They are connected to the mains water supply and deliver hot water at a slightly reduced pressure. Standard units can generally deliver adequate hot water to one or two points simultaneously.
High powered, high efficiency units can serve larger households.
It is vital that units are seized according to the maximum number of hot water outlets likely to be used simultaneously
Some units have electronic remove controls for precise temperature control from inside the house
They operate most economically on natural gas, but can also use LPG and peak rate electricity
Gas units generally require a larger gas supply line than storage systems, potentially increasing installation costs.

SOLAR-GAS OR SOLAR-ELECTRIC CLOSE COUPLE THERMOSYPHONES (TS)
(mains pressure)

Solar-gas water heater systems are some of the most common systems on the market. It consists of roof mounted solar collectors, combined with a horizontally-mounted storage tank located immediately above these collectors.
In these solar systems a pump Is not required. Heated water rises naturally through the solar collectors and enters the storage tank. When this happens, cooler water at the base of the storage tank is forced out and flows down to the bottom of the collectors.
Boosting can be provided by gas or electricity (preferably off peak as it is lower cost). Boost heating in the storage tank (tank boost) should be in the top half of the tank so that solar can heat the bottom of the tank. Alternatively, boosting can be done after the solar storage tank by using a continuous flow gas heater (in-line boost) designed to accept varying inlet temperatures.
This cycle is continuously repeated while the sun is shining. Many commercially available solar hot water systems employ this cycle, commonly referred to as ‘thermosiphone flow’

SOLAR-GAS OR SOLAR-ELECTRIC PUMPED SYSTEMS

(mains pressure pumped)

With a pumped system, the tank is located below the level of the collectors,
usually at ground level. Water must therefore be pumped from the tank to
the collectors and back by a thermostatically controlled pump. Pumps are
generally small and not expensive to run, costing about $10 p/year. This
system can be used when the roof structure is not strong enough to support
the weight of a water tank.

The system can be boosted by electricity, usually off-peak, or gas either
controlled by a timer which stops the gas burner from operating during
sunshine hours or which puts the heat into the upper part of the tank

CONTINUOUS FLOW GAS-BOOSTED SYSTEMS

A continuous flow gas water heater designed to cope with carrying (and often quite high) input temperatures can also be used as a solar hot water booster. In this configuration, the solar hot water heater preheats the water and the gas heater is only used if the water temperature becomes too low. This minimises the contribution from the sun

HEAT PUMPS

Heat pumps are another type of hot water system that run efficiently on electricity. These systems use a refrigerant gas and a compressor to extract heat from the surrounding air. This is sometimes called ‘air source’ heat. The gas then moves along to a coil that is wrapped around the hot water tank where it condenses and gives off the heat it has absorbed to the water in the tank.
Heat pumps are included as electric-boosted solar water heaters as they require similar amounts of electricity to operate.

ELECTRIC, GAS OR SOLAR

Choosing the correct energy source to heat your water can make a significant difference to running costs. The most common fuels for hot water systems are off peak electricity (storage units only) and natural gas.

NATURAL GAS

• Can be used for storage and continuous flow systems
• Systems are rated for their energy efficiency with Energy Rating labels – the more start the more energy efficient
• Internal and external models are available
• Storage water heaters have smaller capacities than off-peak electric systems, as water can be reheated at any time of the day or night

OFF PEAK ELECTRICITY

• Running costs more than natural gas
• Only available for use in storage systems of 160 litres capacity or greater
• Water is heated overnight to provide adequate hot water for daily usage
• Internal and external models available
• Not available for continuous flow system

SOLAR ENERGY

• Provides approximately 60-70% of your hot water free of charge in
Victoria and is very beneficial to the environment
• Generally the cheapest systems to run, but have a relatively high
purchase cost with an average payback period of around 10 years
• All systems come with a gas, off-peak electric or solid fuel booster to
supply adequate hot water during periods of low sunshine
• The panels are generally located on the roof. The water storage tank
can be located on the roof above the panels, within the roof or as a
pumped system at ground level
• Mains pressure and constant pressure systems are available
• Some electricity retailers offer a discounted off-peak tariff for
solar water heaters
• Victorian State Government rebates can significantly reduce the payback period and are now available for new solar hot water installations

LPG

• Used in areas where natural gas is not available
• Running costs average around 2.3-3 times the price of natural gas or off-peak electricity
• Look for the Energy Rating label with the highest number of stars
• Suitable for storage and continuous flow units

SOLID FUELS (wood, briquettes, coal, etc)

• Costs of fuel vary greatly
• Can be used alone, or in conjunction with off-peak electricity and/or solar in constant pressure storage units
• Water can be heated using a ‘wetback’ attached to a slow combustion wood heater, or a stand along water heater powered by solid fuel
• Must not be used with mains pressure systems, unless a heat exchanger is used
• Not available for continuous flow systems

PEAK ELECTRICITY

• Can be very expensive to run so should only be used when other options are not possible
• Common in flats and units, where space is limited and where flueing is difficult
• Used for electric continuous flow units, storage water heaters with a capacity of less than 160 litres and heat pump type storage systems

HEAT PUMPS

• A highly efficient form of water heating which uses around 65% less energy than other electric water heaters
• Have lower running costs than normal peak electric storage units because of their high efficiency
• Heat is extracted from the atmosphere using a refrigerant gas and a compressor (in much the same way as heat is extracted from your refrigerator) and used to heat water stored in a tank at ground level.

WHAT SIZE SYSTEM WILL I NEED?

• The following table can be used as a guide however consult your supplier for specific size recommendations:
• 1-2 people – 160-200 litres – 2m2 collector area
• 3-4 people – 300-370 litres – 4m2 collector area
• 5-6 people – 440 litres – 6m2 collector area

HOW MUCH DOES IT COST?

• Solar water systems vary in price depending on the model, tank size and number of panels. It is often possible to negotiate discounts when purchasing solar hot water systems.
• For an additional investment of around $2000 above the price of a conventional hot water system, a solar hot water system in Melbourne will pay for itself in approximately four to ten years at today’s gas and electricity tariffs. This period will be shortened if tariffs rise.

PURCHASE COST (approximate)

Electricity $800 – $3500
Natural Gas $800 – $2100
LPG $800 – $2100
Solar $2500 – $5000

Small household (1 bedroom , approx 120l/day of hot water)
Medium households (203 bedrooms, approx 200 l/day of hot water)
Large household (4+ bedrooms, approx 300l/day of hot water)

SOLAR HOT WATER REBATES

Metropolitan Melbourne $300-1500
Regional Victoria $400-1600
Rebates vary for solar hot water systems depending on their:
• Size (amount of water produced)
• Performance (solar contribution), as well as relative cost of installation
Australian Government Rebate
The Australian Government’s solar hot water rebate of $1000 to install a solar
hot water system or $600 for a heat pump is available to households replacing
an electric water heater.

For more information visit www.resourcesmart.vic.gov.au/rebates

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Disclaimer: The advice given in this media release is for general interest only. Anyone undertaking renovation, building or maintenance work should consult the relevant professionals. Hire A Tradesman takes no responsibility for work carried out on the sole advice of this column.