This letter present a new resolution of the IEEE Std. 1459 unbalanced power <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(S_{U1})$</tex></formula> . The resolution is intended to achieve a better quantification of the power terms included in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$S_{U1}$</tex> </formula> . The new definitions improve the quantification of the unbalance phenomena presented in the IEEE Std. 1459. The new power terms included in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$S_{U1}$</tex></formula> extend the measurement capabilities of power meters based on this standard.