Yes, WATTS is a Scrabble word!

Letter values in Scrabble US: W 4, A 1, T 1, T 1, S 1.

Is it a valid word?

WATTS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

English poet and theologian (1674-1748)
a unit of power equal to 1 joule per second; the power dissipated by a current of 1 ampere flowing across a resistance of 1 ohm
Scottish engineer and inventor whose improvements in the steam engine led to its wide use in industry (1736-1819)

Also: isaac watts, w, james watt.