metered rate; usage-based charge
A fee calculated according to the amount used, such as for electricity, water, gas, or data.
This plan uses a metered rate system; you pay only for what you use.
The electricity usage charge is divided into three tiers based on consumption.
定額料金 is a flat-rate charge, while 従量料金 varies with usage.
従量料金 is the charge that varies with how much you use a service, whereas 基本料金 is the fixed base fee charged regardless of usage.
Compound of 従量 (based on quantity) and 料金 (fee, charge).