What size of cable will be required to supply a 1.5KW pump 300 metre away

Allowing for a start current of 3 x normal running current and an allowable start volt drop of 20% (down to 176V, as low as I would like to go) you could just get away with 6mm² cable.

How are you running the cable? If on poles then go up to 10mm² (12% volt drop on start) and use single insulated rather than insulated and sheathed.

If cost sensitive go for a size bigger and aluminium cable rather than copper.

Thanks for your help

Edited February 22, 201610 yr by offset

http://www.doncastercables.com/technical-help/

This site has a good online calculator.