What SIESA does

Power Generation

SIESA provides the generation and supply of electricity to consumers on Stewart Island.

Stewart Island has around 405 permanent electricity consumers connected to a distribution network powered by up to five diesel generators at a central power station at Hicks Road. The generation plant consists of a 4(+1) configuration made up of:

  • 1 x CAT 3406 320kW prime output diesel generator
  • 2 x CAT 3408 208kW prime output diesel generators
  • 1 x Detroit Diesel Series 60 360kW prime output generator
  • The standby generator (+1) is a 550kW Detroit Diesel generator capable of supplying the entire island load when necessary
  • The distribution network on Stewart Island is made up of:
  • 14km of 11kV overhead lines
  • 1km of 11kV underground cable
  • 6km of 400V and 230V overhead and underground wiring
  • 43 11kV / 400V - 230V transformers

Frequently asked questions

SIESA often gets asked questions about other options for power supply. Some of the more common questions (and answers) are shown below:

Why can't a cable be run from the mainland to Stewart Island?

Several studies have been undertaken to examine the viability of running a cable from Bluff to Stewart Island. In both cases the idea was shelved due to high capital and operational costs and the inability to guarantee constant supply.

A proposed way forward to deal with electricity supply on Stewart Island (McNeill, R et. al. 2007) suggested costs would be in the order of $9 million. Additionally citing experience of the 1980 NZ Post cable that ran to the Island which sufferedfrom outages due to oyster dredging, anchor snags and other causes (pg 18) the ability and cost to ensure constant supply would be both difficult and highly expensive.

An independent report undertaken by Meridian Energy subsidiary RightHouse Initial Findings and Recommendations from Stewart Island energy efficiency and generation study (Capper, J et. al. 2008) reached similar conclusions. RightHouse suggested that a cable would have a capital cost in the vicinity of $10 million and would have an ongoing maintenance cost of $300,000 per annum. In both instances the net effect of delivering electricity across a cable like this would push the cost to consumers well past existing electricity prices.

Can't we just keep using Diesel?

The simply answer is yes, but electricity prices are directly related to diesel prices. As the cost of diesel rises so will the cost of electricity.

The more SIESA can move away from reliance on diesel, the more likely cheaper, more stable priced electricity can be delivered. The chart below shows in realtime the current cost and forecast cost ($USD) of a barrel of crude oil.

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