Thanks. At first I wanted to charge a fix $150 in addition to the room rental. The tenant is not comfortable with that. He has his own fan, but still must have air con. That's why I told him to pay whatever is shown in the PUB bill. Now the problem is that his sister stays with him, and he works day shift, while his sister works night shift. So the air con is on day and night, sian... He is not too happy about paying the PUB bill, complaining that the tenant in the other room may use more electricity/water.