Boiling Water: Electric Kettle versus Gas Stove

Boiling water is something that many Australians do at least once a day, especially those of us whom enjoy such luxuries as hot chocolate, tea, coffee, cooked vegetables, boiled eggs, soup or pasta. So what are some ways that people can reduce their energy consumption when performing these sometimes daily routines? The most energy and cost efficient way of boiling water can vary depending on the quantity of water needed to be boiled, the efficiency of individual kettles, the type of energy (electricity or gas) and price variations. The table below provides a comparison of time, energy, carbon dioxide equivalent emissions, and costs of boiling water in different ways.  

Comparison of Different Methodsfor Boiling Water

                        **1350W actual use.

Note: Calculations assume a room temp of water of 20 degrees Celsius.  These studies used different volumes of water and this should be taken into account when making comparisons.

 Source: Paster, P (2009). (9); Steer, W.A. (2008). (10).

If say, one mug of coffee is approximately 250 mL of water, 500 mL gives approximately 2 cups of coffee. Hence boiling water for one cup of coffee costs ≈ 40 cents using an electric kettle, $1.00 using an electric stove and saucepan, 3 cents using a gas stove, and 50 cents using a microwave.

If you boil water using an electric stove, rather than an electric kettle, you will produce around three times as many carbon emissions. 

If cooking pasta/rice using approximately 1.5 L of water, boiling the kettle and using the boiled water saves time and energy when compared to boiling the water on an electric stove.  Therefore the kettle will take approximately 5 minutes to boil and cost approx. $2.67 whereas the electric stove will take almost 30 minutes to boil, costing $7.98. In a similar situation using a microwave will cost $3.17 and take approximately 14 mins, whilst using a gas stove will take 18 minutes, costing only $0.18.

From the table above we can see that:

• Electric kettles are faster and more efficient at boiling water than a pot on a traditional gas stove tops. This is because the heating element is enclosed in the water within the kettle which enables the water to be heated directly.
• Power plants that convert coal into electricity, like here in Australia, are less efficient and more polluting than those that convert natural gas into electricity.
• Another option for those with natural gas is to use a stove top kettle.  Using natural gas to heat water in a kettle is also a good energy efficient option.

                Source: Sequoia, Z. (2009)

Natural gas versus coal-powered electricity

• When using coal fired electricity, only approximately 1/3 of the original calorific value of the fuel is used. This is due to the energy loss of converting fuel to electricity and transporting it to homes. Using natural gas consumes 70-80% of the original calorific value of the fuel as it eliminates the need for fuel conversion. Bearing this in mind; gas kettles could be considered to be an overall more efficient way of using energy and can save carbon emissions.
• In Australia, heating water using gas is at least 3 times more efficient and produces as much as 5 times less carbon emissions than using electric means.

Regardless of using gas or electricity, energy and money could be saved using the following tips:

• Try not to forget about boiling water to reduce energy wastage and/or the need to re-heat. Whistling kettles, or kettles that automatically turn off, may help you use the water when it has finished boiling.
• Only fill kettles and/or saucepans to the approximate volume needed. This will reduce energy, time and reduce evaporative loss of the water. Eco kettles have been designed to help people only boil the water they need.
• Alternatively, if you are someone who uses a lot of boiling water in a day, try boiling a set volume once in the morning and keeping the water in a thermos for the rest of the day, using it as you like, any remaining water can be used to water plants.
• Have electric kettles switched off at the power point when not in use.
• Wash electric kettles occasionally to clean out mineral deposits which can decrease the efficiency of the kettle’s heating element.