A tiered plan charges different per-kWh rates for different usage bands, so your effective price depends on how much you use — a low headline tier can hide a pricier one above it. None of the example plans is tiered (they’re all single-rate with cliffs or windows), but the engine models tiers, and the same rule applies: plot the curve and read the price at your usage, not the advertised 1,000 kWh point.