What will be the power consumption if I use dimmerstat for fan or bulb of 60W on slow speed?

A light dimmer on a fan could be problems. A speed control designed for a fan motor would be the correct option. As to power consumption, there is no way to tell without knowing exact settings and initial current draw. The only way to get that information is with the correct test equipment. I do know from testing that a light bulb on a dimmer will use between 80% and 90% of the full load power when it is dimmed to 50% light output. Use the correct wattage bulb. Don't rely on a dimmer to save electric, it is very inefficient.

As EP suggested, dimmers aren't energy efficient, they are just ambiance controls. Although I use them for that purpose, I do not expect nor get energy savings from their use.