Yes absolutely, a spike in electricity usage is perfectly acceptable grounds for them to get a search warrant on suspicion of growing hash using high watt lamps
No, far from it. Aren't there lawyers in Ireland?
Police do not routinely check power consumption. They have no right to do this. Police do not know how much electrical energy you use, this is private information between you and your utility company.
I know in the UK, they have some kind of infrared cameras which allows someone to check if there is excess heat inside a building, but even that is insufficient to enter a property and seize equipment from it.