Most people (in Ontario, anyway) rent their hot water heaters. What happens when you sell your house?
Most agreements will provide that the hot water tank rental is to be assumed by the buyer. Generally, this is quite simple; if your rental is through Enbridge, as most are, it will automatically transfer over to you when you set up your utility account with them. If you rent from one of the smaller companies, however, you must ensure that you provide this information to your lawyer so that the rental can be transferred over to the new owner. Usually this will involve the buyer signing an assumption agreement and new contract on the same terms you had agreed to.
Transferring a rental contract to a new owner is fairly simple, but you have to make sure that everyone is aware of what needs to be done.