To answer your question requires that the Power Factor be know.
The Power Factor ranges from zero to one and is one for a pure
resistive load. If your device is resistive the answer is 1500
watts.
For a typical power factor of 0.8, you can estimate the wattage by multiplying the apparent power in volt-amperes (VA) by the power factor. In this case, 1500 VA × 0.8 = 1200 watts.