1. While vacating the flat had he given any letter to the effect that he is vacating the flat and handing over its possession to you?
2. If not then he can create problem later on claiming that he has never vacated the flat,
3. However, send a notice to him asking him to take back his furniture and pay you the balance electricity bill within 30 days failing which you will be constrained to sell those furniture and recover the said amount,
4. After that publish the notice in two local Newspaper one being in Vernacular,
5. Wait for 30 days after which publish a sale notice in Newspapers in the same way and get those furniture sold,
6. After paying the said pending electricity bill, keep the balance of the sale proceed in an interest bearing bank account.