There are better ways of cutting carbon emissions

Labour has announced its clean energy policy, centred on a plan to generate 100 per cent of New Zealand’s electricity through renewable sources by 2030.

This brings forward its previous target by five years. Similarly, the Greens have announced the same 2030 target, using different methods to get there.

As it stands, around 84 per cent of New Zealand’s electricity is powered by renewables. The major barrier to increasing that proportion is the ‘‘dry year problem’’.

Most of New Zealand’s renewable electricity is generated by hydro dams, which are dependent on weather. In dry years, low lake levels mean supply cannot meet demand, requiring the use of cheap energy (mostly natural gas) to meet the shortfall.

Having enough renewable energy to fill supply troughs requires ‘‘overbuilding’’ – installing more capacity than is actually needed – which comes at a significant cost.

The Government asked the Interim Climate Change Committee (ICCC) for advice. Its recommendation was to not worry about the target at all – there were better ways of reducing carbon emissions, at a lower economic cost.

Instead of reducing electricity-related emissions – about five per cent of the national footprint – it suggested leveraging electricity to reduce emissions elsewhere. In particular, it pointed to increasing uptake of electric vehicles and retiring coal boilers.

Doing so would increase electricity demand – and therefore electricity-related emissions – but the corresponding drop elsewhere would work out better than simply reducing electricity-related emissions.

Labour’s policy nods to this idea, but does not embrace it.

It proposes to bring back its clean car standard, which was thwarted by NZ First, but has little else to drive uptake of electric vehicles.

Labour also wants to ban new thermal electricity generation, but it does not propose to end coal use, as is the case with the Greens’ policy.

It instead pins its hopes on something else the ICCC suggested: Pumped hydro. This is a combination of a hydro dam and a battery. When electricity demand is low, it uses electricity to store water. When demand is high, it releases that water to generate electricity for the grid.

Such a scheme is possible at Lake Onslow in Central Otago. The Government already committed $30 million to a business case, and Labour’s policy pledges a further $70m for the next phase of development.

Labour’s policy puts a lot of faith in the Lake Onslow scheme, or something similar. While the ICCC concluded pumped hydro was the best of all options for addressing the ‘‘dry year problem’’, it pointed to potential pitfalls, both economic and environmental.

Such a scheme would have numerous benefits – it would employ thousands of people, and drive power prices down but in terms of the climate, it will not drive emissions reductions to the maximum possible extent.

– Stuff is tackling the big debates and key issues of the election campaign in The Whole Truth, a factchecking project