Industry information


This page provides information about pricing, rentals and transmission agreements.

Value of Lost Load (VoLL) study

We have undertaken an investigation of the Value of Lost Load (VoLL) to inform our expenditure decisions and regulatory applications.

VoLL represents the economic value, in dollars per MWh, that a consumer places on electricity they plan to consume but do not receive because of a power interruption.  It is different in concept to the price consumers pay in the wholesale and retail markets for electricity.  Both the wholesale and retail prices reflect consumers’ demand for electricity, whereas VoLL reflects consumers’ demand to avoid power interruptions and its consequences. 

Options to relieve Central North Island transmission constraints

In a series of reports published in March 2016, we highlighted that transmission capacity from Bunnythorpe to Whakamaru is constrained by the capacity of the 110 kV Bunnythorpe–Mataroa and 220 kV Tokaanu–Whakamaru circuits.  With the decommissioning of thermal generation in the Auckland region, the risk of these constraints binding increases. 

We have identified some low cost options to relieve these constraints in the short-term which include:

Operational Review 2

Latest update: January 2018

In June 2017, we released an Invitation to Comment on a possible Operational Review 2 of the Transmission Pricing Methodology (TPM). This was following the Electricity Authority announcement that it needed to prepare a new cost-benefit analysis before any decisions could be made about its review into the TPM Guidelines.

Market impact assessment from changes to HVDC cost allocation

The methodology to allocate the HVDC costs to South Island (SI) generators was changed in 2015. This change involved transitioning from the peak-based metric (HAMI) to an average-based metric (SIMI) from the 2017/18 pricing year (PY). The allocation based on HAMI resulted in a strong incentive for SI generators to maintain generation below established HAMI levels (HAMI limits) thus avoiding increased allocation of HVDC costs. The change to SIMI was intended to reduce this incentive, thus increasing the availability of SI generation capacity.

Ten Year Forecast of Fault Levels

This publication presents an update to the ten year forecast fault levels report. The Connection Code contained in Schedule 8 to the Benchmark Agreement requires Transpower to publish a ten year forecast of the expected fault levels at each customer point of service annually.

Transpower last published the Ten Year Forecast of Fault Levels in September 2015.



HVDC bi-pole trip and change to under frequency reserve risk: technical commentary

On 11 December Transpower’s HVDC equipment suffered a bi-pole trip while transferring 90 MW to the North Island. The cause was unexpected and, while an explanation was quickly found, it was deemed necessary to change the risk treatment of bi-pole trip risk from ECE to CE until a fix could be determined. This change in risk status, with consequent market impacts, lasted 8 days until an interim fix to the faulted assets could be implemented.  A permanent fix will be developed and implemented in 2016.