There sure are, and that’s mostly thanks to daily and seasonal trends in our power usage. We Kiwis usually use more electricity during peak times of the day and night (when we’re all at home having breakfast or cooking dinner), and in the winter months, so the available supply is reduced and spot prices are sometimes pushed up. Plus, sometimes we’ll see a rise in prices when there’s a shortage of renewable generation (for example, if hydro lakes are low during summer).
Spot prices tend to drop during off-peak hours (hence the name!), like during the day and in the middle of the night. Prices also tend to be cheaper when there’s lots of wind and rain to power our renewable energy generators, and during the warmer months when we’re using less power.