The Electricity Act Article 48

Electricity-Retailing Utilities may charge a set fee based on a minimum usage level per month or based on the capacity required by the user.If the Public Electricity-Retailing Utility charges a fee based on a minimum monthly consumption level, as described in the preceding paragraph, the user shall be charged based on actual usage if the actual monthly usage exceeds said monthly minimum.
中文原文 電業法第48條
公用售電業得訂定每月底度或依用戶所需容量收取一定費用。
公用售電業定有前項每月底度者,其用戶每月實際用電度數超過每月底度時,以實際用電度數計收。

English translation for reference only; the Chinese text prevails. Not legal advice.