15 x 115 = 1725 watts, 7.5 x 230 = 1725 watts ... or 1.725 kW every hour its on.
1.725 x (hours per day the pump runs) = kW/h used per day
(kW used per day) x (cost per kW/h delivered from your electric company) = cost to run pump per day
That's its rated power consumption running at full load. Since a single speed pool pump is always running at close to full load that's a pretty good guess as to how much it is using. Short of actually measuring its power consumption with a meter.