With reference to notification no.: 14/2018-Central Tax(Rate) Dated: 26-07-2018 of Finance Ministry, the Indian government

Services supplied by electricity distribution utilities by the way of construction, erection, commissioning or installation of infrastructure for extending electricity distribution network up to the tubewell of the farmer or agriculturist of agriculture use, GST should be zero

It will be effective since 27-07-2018. So, No GST will be charged while preparing an estimate for the PTW connection