(1) "Residential customer" means a residential customer of a distribution utility.

(2) "Small customer" means a residential customer or a small natural gas commercial customer of a distribution utility.

(3) "Small natural gas commercial customer" means a commercial natural gas customer with usage per year on an individual account which averages under 500 dekatherm units (dkts) or 500 mcf (each mcf unit is one thousand cubic feet) or a new commercial customer whose individual account is estimated to average a monthly usage under 500 dkts or mcf per year.