[jarek]

British Columbia, where hydroelectricity is cheap and plentiful, has a two-tier structure like that. The cut-off isn't exactly 1000 kWh, of course.

The logic is that the utility company plans for generating a "usual" baseline amount, and peaks and use beyond anticipated "norm" are more expensive since you have to spin up/buy additional capacity. In B.C. at least the tiers are set up so that the first category will cover most "average" use.

Also in many places electricity prices are government-regulated to a greater or smaller extent, and a government might structure pricing like that to try to reduce overall energy use or subsidize the lowest users who might be presumed to be poorest.