During each half-hour period Transpower publishes a new real-time price every five minutes, and a time-weighted 30-minute average price. The real-time prices are used by some large direct-connect consumers to adapt their demand. The prices are however guidelines only as the final prices are calculated ex-post - normally around 10:00am the following day, unless there are irregularities or disputes. Using the offer prices as established two hours before the trading period and volumes as established during the trading period. Differences between forecast, dispatch, real-time and final prices can be significant.