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The Stewart Island Electrical Supply Authority (SIESA) is responsible for the generation and supply of electricity to consumers on Stewart Island. SIESA is owned and operated by the Southland District Council on behalf of Stewart Island electricity consumers and is governed by the Stewart Island Community Board.

SIESA also undertakes waste collection and ownership and operation of the Rakiura Resource Recovery Centre.

Oban, Stewart Island, New Zealand

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Future of Electricity on Stewart Island

Venture Southland is currently measuring the wind, solar and hydro energy potential at three locations on Stewart Island on behalf of SIESA. Data from these locations may be viewed here. The data are uploaded from the recording stations weekly.

Please click on the web link below and use the following username and password to access the information.

Username - Stewart-Island

Password - WindHydroSolar


Please read the Edging Towards Sustainability Report.

Please read the Edging Towards Sustainability 2 Report.

Energy Futures Workshop February 2012

Stewart Island Energy Futures Workshop, 24th February 2012

Southland District Council in conjunction with Venture Southland ran a workshop at Oban for vendors and experts to present to the local community the options and difficulties to implement full, or partial replacement of the current engine-alternators with the view to minimising the cost of electricity on Stewart Island. The intention was to seek community consensus for investigating, or otherwise any, or all options.


The workshop was held at the Oban Community Hall on Friday 24th February 2012, starting at 1:00pm, finishing at 6:30pm. Some 50 - 60 people attended in addition to the presenters. Most people attending were Oban rate-payers, but some members of the audience had come from as far away as Auckland and Christchurch.

The programme was devised to consist of three sections: the first was to set the scene and explain legislative and planning constraints for options; the second session looked at the technology options available. The third and last session comprised a presentation on the Meridian wind power scheme at Ross Island, Antarctica, which has many lessons for Oban.

Colloquium opening

Councillor Bruce Ford

Jon Spraggon, Stewart Island Community Board,

Erik Barnes, Southland District Council

Session I: Setting the Scene

Introduction to session

Robin McNeill, Venture Southland

World and National Trends and Developments in Energy generation and Use Accompanying Commentary.

Emeritus Professor Arthur Williamson, University of Canterbury

Stewart Island Electricity Demand and Supply Summary of Progress to Date

Robin McNeill, Venture Southland

Environmental Matters

Sharon Pasco, Department of Conservation

The Resource Management Act and Energy

Kylie Galbraith, Environment Southland

How EECA can assist remote communities

David Rohan, EECA (not present at the workshop due to illness)

Session II: Technology Options

Introduction to session

Grid Stability Issues HVDC-Lite from the South Island Grid

Dr Hamish Laird, ELM G

Small Hydro Opportunities for Stewart Island

Jeff Wilson, Wilson Hire

Is Hydrogen Storage an Option for Stewart Island?

Dr Alistair Gardner, IRL

The SHED (Southland Hydrogen Economy Development) Project

Anthony Hine, REACH Power Ltd

Partial Gas Substitution for Industrial and Marine Engines

Basil Walker

Wind Potential for Stewart Island

Dr. Phil Murray, Massey University

The Tangaroa Marine Energy Trial near Oban

Stewart Island Project Briefing

Langlee Awatea Presentation

Kevin McGrath, Tangaroa Energy

Session III: Scoping the Future

Remote Island Power Supply Case Study: Ross Island, Antarctica

Iain Miller, Antarctica New Zealand

Colloquium Round-up

Erik Barnes, Southland District Council


McNeill, R.G. A Proposed Way Forward To Deal With Electricity Supply At Stewart Island (2007)

Will the price of electricity drop on Stewart Island?

It is too early to know if renewable energy sources do indeed offer the possibility to reduce the cost of electricity at Oban: no-one knows for sure if the waves are big enough and often enough; if the wind can be relied on; if a hydro scheme would really be viable, or if the cost of solar panels is yet cheap enough. On the other hand, the presenters at the workshop overwhelmingly believed that the price of diesel would only increase over time and some harboured concerns for international long term certainty of supply. It may be that renewable energy sources can at best only halt price increases. Only by collecting site data over a year or so can the economic viability of renewable generation be truly understood.

Next Steps

Venture Southland and Southland District Council staff will work together to produce an options paper for the Stewart Island Community Board and subsequently to be posted on this site setting out the next steps to be taken.

Summary of Stewart Island Energy Futures Workshop, 24th February 2012

What we do

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 suffered from 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) found similar findings. 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.

    Graph provided by www.oil-price.net. Note prices shown in $USD.

Contact SIESA

We welcome you to contact us with any feedback or anything else you would like to discuss. Contact details for SIESA are as follows:

Phone: 0800 732 732
Fax: 0800 732 329

Or you can visit your local Southland District Council office:

Stewart Island: 9 Ayr Street, Oban
Invercargill: 15 Forth Street, Invercargill

Feedback and Complaints

If you have a complaint about SIESA we encourage you to contact us through any of the means above. There is no charge to lodge a complaint with SIESA and your feedback is important to us. If you have raised a complaint with SIESA, and;

  • You are not satisfied with how we propose to deal with your complaint; or
  • We have not resolved your complaint within 20 working days of receiving your complaint and we haven't explained why we need additional time; or
  • We have not resolved your complaint within 40 working days of receiving your complaint,
If we cannot resolve your complaint, you can contact Utilities Disputes on 0800 22 33 40 or go to www.utilitiesdisputes.co.nz . Utilities Disputes is a free and independent service for resolving complaints about utilities providers.
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