If you want to help the environment, you are better off buying an electric car than putting solar panels on your house says a report by Wellington-based Concept Consulting.
It looked at the impact of electric cars and residential solar power systems on New Zealand's carbon footprint, and has prompted the Parliamentary Commission for the Environment to call for people to take heed.
The report says solar panels generating power for households have less impact on carbon emissions long-term because the solar generation will end up substituting other renewable electricity generation, such as wind or hydro power.
"This is different to what happens in most other countries. It is because most of New Zealand's electricity is generated from renewable sources (hydro, wind and geothermal), and the fact that large-scale renewables also represent the least cost option for future electricity supply in New Zealand – something that is not the case for most other countries," the report said.
Electric cars would usually be charged during times when there is less demand for electricity, the report says.
"Looking out even further, we expect solar photovoltaic (PV) cells to modestly increase the need for fossil-fuelled generation, and therefore add to electricity sector emissions. This counter-intuitive result is because solar PV generates more power in summer than winter - the opposite of New Zealand's power demand needs."
"To fill a widening gap between winter power demand and supply associated with high PV uptake, New Zealand will need more power from controllable sources that operate for only part of the time.
"We expect this to be met mainly from operation of fossil-fuelled power stations, as existing hydro stations are limited in their ability to further increase the amount of water they store in summer to release in winter."
But electric vehicles could largely eliminate carbon emissions from petrol and diesel.
Concept says an electric vehicle could cut annual carbon emissions by up to 1.7 tonnes over the long-term. The vehicles would be charged from low-emission power sources in New Zealand and usually at off-peak times, such as overnight.
Transport Minister Simon Bridges has been criticised for his lack of a clear electric vehicle policy. A package of measures to increase uptake had been planned by the end of last year.