Efficient Hot Water

The average home uses about a quarter of the total energy consumption to heat water. As you reduce energy use in other areas, like lighting, heating and cooling, this percentage will become bigger and more significant. Finding the most effective hot water service for your situation requires knowledge of the different types of systems and their strengths and weaknesses.

EnviroShop are experts at installing the very best evacuated tube solar hot water systems and heat pumps for residences. Our hot water systems are carefully selected based on performance, reliability and long-term durability. Almost a quarter of the average household’s energy costs can go to heating water. Installing a solar hot water system is one of the most effective ways in which you can save energy and reduce your carbon footprint. Not only that, the government offers generous solar hot water rebates to make solar hot water even more affordable. For quality solar hot water systems, residents and businesses choose EnviroShop to deliver an effective energy saving solution.

Sanded Heat Pump hot water system with a solar electricity inverter - a great pairing.

Sanden Heat Pump hot water system with solar electricity – a great pairing.

Conventional hot water systems last around 10-15 years. By replacing your old system with our solar hot water systems, you’ll avoid the inconvenience of it failing and get a head start with your solar savings.

When your old hot water system fails you’ll want hot water in a hurry. We can usually provide an emergency hot water system to give you time to choose the right solar hot water solution for you.

 

To find out all you need to know about solar hot water in Melbourne, call us now on (03) 8395 3030 or complete the enquiry form and we will contact you.

  • Evacuated Tube Solar Hot Water Systems
Evacuated Tube Close Coupled Hot Water System

Evacuated Tube Close Coupled Hot Water System

 

The Science of Heating Water

It’s a luxury to simply have a hot shower or bath whenever you want, however getting reliable and safe hot water ‘on tap’ is more difficult than you’d think.

It takes a LOT of energy to heat water. There is a measure of how much energy it takes to increase 1 gram of a substance by 1 degree Celsius known as Specific Heat. Most common substances have a specific heat of much less than 1. Water has a specific heat of more than 4. This means it takes many times more energy to heat water than it does almost anything else. When you waste hot water, you’re wasting a lot of energy. Minimise your hot water use around the home with behaviour change and efficient fittings, but also make sure external connections on your hot water tank and the pipes are insulated and if you’re designing a new build or renovation minimise the length of hot water runs from the heater to the outlets.

Water is a great growth medium for bacteria and other disease-causing organisms. Mains water is treated with chlorine to slow the growth, but warm water speeds it up. For safety, water should be stored at more than 60 degrees Celsius, but much more than this is a waste of energy, so set your hot water thermostat appropriately.

The overall efficiency and environmental impact of your water heating system depends a lot on how much you use and when you use it. Where the energy used to heat the water comes from also has a major impact. Most of our energy originally comes from the sun, even coal, so the closer we get to the primary source the better. This means solar water heating or heat pumps are usually the best choice for most situations. There are times when an instantaneous heater or very small electric storage system makes more sense though. Ask our consultants for advice on your situation.

Heat Pumps

Heat pumps have been around for a long time in the form of fridges and freezers, for quite a while in reverse cycle heating and cooling systems and most recently as water heaters. They work by ‘pumping’ heat from one place to another, using a compressor and a refrigerant. In the case of your fridge it is pumping the heat from inside the cabinet to the room outside. In the case of a heat pump hot water system they are pumping the heat from the outside air, which has been heated by the sun, into the water storage tank.

They are very efficient at heating because instead of converting electricity (or gas) into heat it uses a much smaller amount of energy to move heat from elsewhere. In Australia we mostly use air-sourced heat pumps, but in colder climates ground-sourced heat pumps are more common.

The measure of efficiency is the COP, or coefficient of performance, a ratio of energy consumed to energy provided. Higher is better. Good units usually have a COP of around 4, which means they use around 75% less energy than an electric hot water system. When they are paired with a solar PV system to provide the electricity they can be 100% solar powered, with typically no running costs, compared to a solar hot water system that requires boosting in the Winter.

Like solar hot water systems, heat pump hot water can be split, with the tank separate to the heat pump, or integrated, where the heat pump is on top of the tank.

Solar Hot Water

Solar hot water works by absorbing sunlight and using it to heat water. The sun is free and renewable energy, but in Melbourne’s climate zone it will only provide around 2/3 of the energy required to heat your water year round. The rest is made up by a booster, which is usually an electric element in the storage tank or an external instantaneous gas system.

There are two main types of solar collectors, flat plate and evacuated tube. Flat plate systems are pipes in an insulated box with glass at the front. While simple and cheap, it is difficult to insulate the pipes against heat loss while still exposing them to the sun.


Evacuated tubes work like a thermos, with two layers of glass with the air evacuated from between them. The inside is coated to very efficiently absorb sunlight, but the heat can’t easily escape back through the vacuum. This makes them more efficient than flat panels when the air is cold.


Solar hot water systems of both collector types can be either close-coupled or split. Close-coupled systems have the water storage tank mounted above the panel. The water naturally circulates, with cold water sinking down into the panel where it is heated and then rises up to the storage tank by convection.


Split systems have the storage tank at ground level. A controller senses the temperatures in the tank and at the collector and controls a pump to move the water up to the collector and back.

Other Hot Water Systems

Electric Storage – a tank with an electric heating element in the water.
Electric Instantaneous – no storage, just a high power electric element that heats the water as it passes over it.
Gas Storage- a tank with a gas burner under it.
Gas Instantaneous – no storage, just a gas burner that heats the water as it passes over it.
‘Wet-back’ wood heating – a system that circulates water around a wood stove to provide hot water in Winter. Can be used as a booster to a solar hot water system.

Hot Water System Efficiency


This graph shows relative efficiency of hot water systems in the Victorian climate by comparing energy consumed from gas or electricity to energy put into heating the water.

Not that this graph represents efficiency of energy use and does not reflect costs of running or greenhouse gas emissions. Gas is still cheaper than electricity and has a lower Greenhouse Gas emissions factor than coal-fired electricity, particularly Victorian brown coal power.