Progressive tariff
tiered tariff · increasing block tariff
A progressive tariff charges a higher unit price for the extra electricity used as consumption rises.
Residential electricity bills split a month's use into several tiers. Only the amount above a lower tier is charged at the higher tier's price; the high price does not apply to all of the use at once.
How to read it: the progressive tariff is meant to encourage saving. The trade-off is that bills can jump sharply in high-use months such as summer.