For a very rough upper limit of the switching power dissipation of a logic level mosfet when switching an inductive load, I use the following formula:

P = 2VIQfR [edit: corrected formula]

where V is the switched voltage, I is the switched current, Q is the total gate charge of the mosfet, f is the switching frequency and R is the gate series resistor (min. 100 ohms). For a resistive load, you can use 0.5 in place of 2. The actual switching power dissipation is likely to be somewhat less than this figure.