Amber Electric is an Australian energy retailer which uses a different financial model to most energy retailers. Instead of marking up the cost of energy and daily service charges in order to cover the variability and risk of wholesale energy prices, Amber instead charges a flat fee for access to the wholesale rates for electricity. The wholesale rate changes each 30 minutes based on the demand and what is producing power at the time.
This model works great for people who would like to save on their electricity bill, and use more green electricity (which is the cheap stuff), and is happy to shift the usage of their energy-intensive devices. In practice, greener the power you use, the cheaper it tends to be. Amber is cheaper than other retailers for most people regardless of whether you choose to shift your energy usage to cheaper times or not, but by avoiding using lots of power in the occasional and short time periods where the price is much higher, you can save significantly more, use less coal and gas power, and help stabilise the grid (because the expensive time is usually when there is high demand).