usage-based billing; metered billing; pay-as-you-go
A billing system where charges are based on actual usage or consumption, common for utilities, cloud services, and mobile data plans.
This cloud service is usage-based; you pay only for what you use.
電気料金は従量制なので、節電すれば請求額が減ります。
Electricity rates are metered, so if you conserve energy, your bill goes down.