Electrification is not just about getting off gas – efficiency matters, too

Electrification can increase or decrease carbon emissions. It depends how and when you do it.

The graph shows the trend in annual emission intensity of using grid electricity and fossil gas in Victoria for a range of end-use efficiencies. While Victorian electricity emission intensity has halved over the past couple of decades, it is still high.

Installing a resistive electric storage hot water service or running a fan heater on average grid electricity to replace will increase emissions now and for some years to come.

Victorian electricity emission intensity trends at 100% and 300% end use efficiencies (eg heat pump COP 3) – kg CO2e/kWh (source Emissions intensity profile – VIC | Australian Energy Regulator (AER)) compared with fossil gas emission intensity (from National Greenhouse Accounts Factors: 2024 – DCCEEW) and adjusted using 3.6 megajoules/kilowatt-hour of electricity equivalent – this generously assumes 100% efficiency of gas use.

Shifting from inefficient gas use to high efficiency electricity does cut emissions now, as shown in the graph.

Depending on the relative efficiencies of the gas and electric options, Victorian grid electricity could still create higher emissions than gas until the mid 2030s. In contrast, a heat pump hot water service or reverse cycle air conditioner will cut emissions from today and emission reductions will increase over time.

The actual outcome depends on several factors.

Efficiency matters

Efficiency of use of gas varies widely. For example, a gas storage hot water service delivering 50 litres/day for a small household may be 30 percent efficient but if it delivers a typical household’s 125 litres/day its efficiency may be around 50 per cent: the substantial fixed standby emissions from the pilot light and tank heat loss are spread over larger amounts of gas.

Measured efficiency of a sample of ducted heating systems varied from 30 to 76 per cent. This ignores the significant increase in air leakage that can occur. 

The graph shows the impact of varying gas and electricity end use efficiency. 

Many industrial and commercial gas systems are difficult to control and have high “standby” losses, for example from poorly insulated distribution pipes, are left running longer than really needed, or heat larger areas than necessary.

Limited monitoring of gas consumption and delivered services means few gas users know how inefficient their equipment is. If gas efficiency is overstated, it can lead to installation of larger, more costly electric equipment than is actually needed – or rejection of an electrification proposal as too costly.

Real time and location efficiency and emission intensity of electricity vary widely. 

As can be seen on openelectricity.org.au, the emission intensity of electricity (and wholesale price) varies all the time, as the mix of generation sources changes. It is usually lower during daytime, especially when it is sunny.

Consumers with rooftop solar, especially when combined with battery storage, reduce their emission intensity. Exports from PV systems may displace use of fossil fuel sourced electricity. Participants in demand management schemes that target low prices may shift consumption to times of lower or higher emission intensity.

End-use efficiency of electricity can impact greatly on the amount and timing of electricity consumption. Heat pumps and induction cooking are much more efficient than gas alternatives and cut emissions: an example of 300 per cent efficiency is shown in the graph. Some heat pumps and reverse cycle air conditioners are much more efficient than that!

Even “low efficiency” electric solutions can achieve high efficiency and reduce emissions by precisely targeting energy delivery, being located where energy is needed, and varying output to match demand. This flexibility, especially if energy storage is used, can also allow consumers to use low-priced electricity. 

Long Single Wire Earth Return powerlines the serve rural electricity consumers can have very high power losses up to 50 percent, especially at times of high electricity demand.

Powerline losses increase with the square of the electric current flowing and with distance. So using one kilowatt-hour in some circumstances may require 2 kilowatt-hours of generation – and associated carbon emissions.

Inefficient gas and electricity use for activities that contribute to summer or winter peak demand increases fixed energy supply infrastructure costs and involves higher capacity, more costly appliances and equipment. Thermally inefficient buildings heated and cooled by inefficient gas and electric equipment are costing a lot and stressing energy supply infrastructure. 

We need to efficiently and flexibly electrify, and also replace inefficient electric technologies and help consumers to improve efficiency of existing electricity usage. We also need improved monitoring of both gas and electricity, combined with improved analysis and reporting of the data. 

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