KiwiRail's plan to power up trains equals less carbon emissions

Most of Wellington’s metro trains use electricity to carry us backwards and forwards to our work, to town, to see our friends and go to a movie. Combined with our Auckland metro friends, that adds up to around 25 million passenger trips per year, or put differently, 88,237 fewer tonnes of greenhouse emissions than if we were to take the car.   

We love that trains are better for the environment, and in the next couple of years Wellington’s last remaining diesel passenger trains are being switched out for the lower-emissions battery electric hybrids.   

KiwiRail and Greater Wellington are on a mission to replace the diesel trains that work the Wairarapa Line, and Manawatū Line north of Waikanae, with new battery electric services from 2029. As well as less carbon emissions, there’ll be more services which will make it easier to catch a train when you need one, and more reliable because they’re new. At the same time KiwiRail is doing a whole lot of work to upgrade the line ready for the faster and more frequent services.    

More battery electric trains are going to need more electricity, so it’s also time to upgrade the power system.   

KiwiRail’s Senior Project Manager Peter Coles says work is underway to introduce five new substations to the network to create the capacity for the new trains, as well as upgrading the existing substations to make what we have now a lot more resilient. 

“A substation is essentially a power converter. It carries electricity from the local supply and converts it from AC power to DC – the voltage type and level needed by the trains.    

Thanks to government funding, there will be three more substations for the Hutt Valley and Wairarapa Line, and two more for the Kāpiti line. 

“The new subs will lift capacity overall, and are crucial for the arrival of the battery electric trains and extra services coming to Wairarapa and Manawatū.    

“As we bring the additional substations into the mix, we can upgrade some of the older 1950s vintage subs for their modern day counterparts, and ensure power distribution is matched to current and future demand.” 

Work begins at Naenae just north of Naenae Station in late 2025, followed by a replacement at Pomare, and new substation at Trentham. Kāpiti line works will begin as Hutt Valley Line reaches completion.   

Mr Coles says substations are good news for supporting that shift from road to rail-based transport.    

“A growing, vibrant region like ours needs a transport network to match. Commuters in our part of the world are good at public transport. We’re doing our bit to make trains the easy choice.”  

   
Facts and figures: 
  • Substations carry electricity from the local supply and convert it to the voltage needed by the trains.  
  • Thanks to government funding, KiwiRail is extending the current 18 substations to 23 in total across the Wellington Region.   
  • Locations for new substations are Naenae, Pomare and Trentham for the Hutt Valley / Wairarapa services, and Tawa and North Junction (South of Paekakariki) for the Kāpiti / Manawatū services.    
  • Substations are built off site and lifted into place to keep disruption to a minimum. 
  • The reduction in carbon emissions by switching to the new battery electric locomotives, will be a positive reduction for our Scope 1 emissions footprint.  
  • Government has invested $137 million in increasing the number of substations and upgrading others feeding power into the Wellington network, saying that’s it crucial to improving reliability for increased services, and resilience when faced with extreme weather events.