Understanding EV emissions

Renault Zoe at EV Expo

Does it really make a difference to your emissions if you buy an EV but run it on fossil fuel generated electricity, compared to sticking with the petrol guzzler? Bryce Gaton re-examines this issue.

Does owning an EV make any difference to your personal transport emissions? In the light of recent statements about EV emissions from Liberal MP Craig Kelly, it seemed a good time to revisit my 2012 analysis of carbon emissions from electric vehicles (EVs) versus petrol vehicles.

In 2012, the result was positive for the only new EV available in Australia at that time—the Mitsubishi iMiEV—when stacked up against a comparable small car, the Toyota Corolla. The iMiEV had lower emissions when driven in all states in Australia on the ‘city cycle’ (modelling typical car use around the city). Only in Victoria on the ‘combined’ city/country cycle did the EV have slightly higher emissions—and that situation could be avoided if it was charged using solar and/or GreenPower.

Six years later, the grid has changed, and the EV and petrol car offerings have changed. So has the result changed too?

To investigate this, I will look at three scenarios for calculating your personal transport CO2 emissions:

  1. Buy an EV for city driving, but take no other CO2 reduction measures.
  2. Combine an EV with a solar array at home.
  3. Other methods for reduction of CO2 for EV electricity consumption.

Scenario 1:
Buy an EV for city driving, but take no other CO2 reduction measures

For this scenario, the answer will depend on where you live. Individual states and territories continue to use different mixes of brown or black coal, natural gas, hydro, wind and solar to generate electricity used in EV charging. These different generation methods produce different amounts of CO2 and other greenhouse pollutants (together referred to as CO2-e).

For petrol- or diesel-powered internal combustion engine (ICE) vehicles, the figures generally stated for CO2 emissions are not the full story. For ICE vehicles, CO2-e includes the CO2 from combustion, plus the direct greenhouse potential from CH4 (methane) and N2O (nitrous oxide) and the indirect emissions from extraction, refining and transport. Adding in these factors enables an ‘apples-for-apples’ comparison.

These factors for both electricity and petrol emissions are sourced from the National Greenhouse Accounts (NGA) Factors report published by the Department of the Environment and Energy and last updated in July 2017. The data on energy/fuel use is sourced from the Green Vehicle Guide (www.greenvehicleguide.gov.au, see note 2).

Read the full article in ReNew 143.