I haven't been in this situation, though my parents have. If I were the tenent, I would be hopinng the landlord would see it as a valuable addition to the house which would increase its appeal to future tenents. As the landlord, it depends on the house and what heating/cooling mechanisms it already has, and where it's situated geographically. If it's somewhere that only gets a few uncomfortably hot nights per year, I'd say no. I believe my parents were happy to comply as the tenents were very desirable, quite long term, and offered to go halves in the cost. The tenent could choose to buy a standing fan for each room - ceiling fans are not the only option for them.