EVs more useful than solar in New Zealand’s clean energy future

Renault's ZOE model
Renault's ZOE model

Electric vehicles are far more useful to New Zealand for reducing carbon emissions than rooftop solar power, a study by energy industry consultants Concept has found.

The Wellington-based consultancy published its findings in the first of three reports backed by Consumer New Zealand, the Energy Efficiency and Conservation Authority, three major electricity retailers, and three electricity network owners.

It concludes photovoltaic electricity generation, mainly through rooftop solar installations that can be linked to battery storage, will have less impact on carbon emissions in the long term than EVs because solar will start substituting other renewable electricity generation options, such as wind, geothermal or hydro.

EVs, on the other hand, will largely eliminate carbon emissions from petrol and diesel because so much of New Zealand’s electricity is generated from renewable sources.

The report, Electric cars, solar panels and batteries – how will they affect New Zealand’s greenhouse gas emissions?, conservatively expects each EV purchased in the near to medium-term to result in an average carbon emissions of approximately 1.4 tons per year, rising to 1.7 tons for EVs purchased further into the future. By comparison, Concept expects a 4kW solar PV panel installed in the near-to-medium term to have a much smaller net effect on emissions – the saved electricity sector emissions largely offset the embodied emissions.

“We expect the electricity sector emissions saving to decline over time, as solar PV panels increasingly substitute for generation from new wind and geothermal plants. As a result, over the longer term, we expect a 4kW solar PV panel installed in the longer term to increase emissions by about 0.25 tonne per year,” the report said, acknowledging this adverse CO2 effect of solar panels is expected to be worse if CO2 prices are high.

“For a 7kWh household battery by itself, we expect an emissions reduction of around 0.1 tons per year, and this does not change much over time. However, this saving could be reduced or eliminated if there is widespread uptake of EVs that are predominantly charged at off-peak times.

“These results are not surprising given New Zealand’s carbon footprint. At present, the average New Zealand household is estimated to directly cause annual emissions of approximately 7 tCO2. The vast majority of these direct household emissions are from vehicles.

“Overall if consumers wish to spend money on new technologies to deliver environmental benefits, by far the biggest emissions saving can be achieved from investing in EVs, whereas batteries and solar PVs have less benefit, and PVs are expected to increase net emissions in the longer term.”


The study is highly specific to New Zealand for two reasons. Firstly, in most countries, EVs would be drawing more electricity from fossil fuel-sourced electricity generation than renewable, where renewables are a small part of the electricity mix. However, renewables already provide about 80 per cent of New Zealand’s electricity mix. Secondly, unlike hot countries such as Australia, New Zealand’s peak energy demand is in winter for heating rather than for air-conditioning during summer, when solar generation is also most available.

“Increasing the seasonal gap between winter power demand and supply would likely increase the need for fossil-fuel power stations that operate on a seasonal basis, noting that New Zealand’s hydro stations are limited in their ability to increase the amount of water they store in summer to release in winter,” the report said.

While surprising at first glance, Concept director Simon Coates said the results make sense.

“Most of New Zealand’s electricity is generated from renewable sources. Adding solar panels basically means that New Zealand will need to build fewer renewable power stations – with little or no net carbon saving,” he said.

“On the other hand, EVs directly displace emissions from fossil-fueled vehicles and in New Zealand, the power to charge EVs will come mainly from renewable power stations. This means EVs provide significant net savings.”


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