Can I connect sonoff pow to direct Mains? as I want to monitor entire home energy consumption
Yes
Please check google before asking the forum for these kind of questions, thanks
Would be good to also use a more descriptive message subject 
Pay attention to the maximum possible load of this device.
To clarify - you need a POW for each device you want to monitor ie: one for your dishwasher / one for your washing machine etc
These devices will plug into mains - correct
You CANNOT plug ONE Sonoff POW device in to monitor your whole house energy consumption
It all depends on the goal you want to achieve. As long as you do not exceed the maximum power and you stick to monitoring a single phase you can use the pow to monitor summed consumption. It will be tough to distinguish between the different power contributors though (for that you do need single POW per device).
@praveen_kumar: little side remark. if you are not too familiar with mains supplies I would however not recommend adapting it other than with single POW after the wall socket as @pgt suggested.