这种按需付费的电费计划适合用电量不大的家庭。

This ___pay-as-you-go electricity plan is perfect for households with low usage.

我更喜欢这种即付即用的手机套餐，因为它不需要长期合约。

I prefer this ___pay-as-you-go phone plan because it doesn't require a long-term contract.