Declining hydro storage and demand in September
While the month of September saw an overall decline in hydro storage as a percentage of average a large reduction in
demand due to warmer spring temperatures resulted in a slight reduction in monthly average prices when compared with
August prices.
Monthly average prices at the Otahuhu, Benmore and Haywards reference nodes all decreased in September in comparison to
August figures. Benmore prices decreased slightly from 2.69c/kWh in August to 2.67c/kWh in September and Otahuhu prices
decreased from 3.31c/kWh to 3.28c/kWh respectively. The monthly average price at Hayward’s decreased significantly from
3.95c/kWh for August to 2.97c/kWh in September. As reported last month the average monthly price at Haywards for August
was severely inflated by a price spike to approximately $12/kWh price that occurred on 21st August.
For the first half of September flows over the HVDC inter-island link were restricted to 700MW. This limitation was a
continuation of the restriction that followed an unplanned outage on 23 June and continued throughout August. Price
separation did occur in September due to the restricted HVDC capacity however it was not as extreme as in August. The
highest price differential between Haywards and Benmore spot prices was 6.81c/kWh at 17:30 on 1st September.
Daily demand during September was at a markedly lower level than that recorded during August. Daily demand exceeded
120GWh only once during September. That compares to 14 days in August when this was exceeded. Average daily demand in
September was 109.2GWh compared to 116.5GWh in August and 113.7GWh in September 2003.
Inflows in September were 97% of average and at month end storage was 97% of average for that time of the year. Storage
levels decreased by 367GWh from 2,518 on 1st September (the highest level during September) to 2,151GWh on 30 September.