One of the greatest signs of trust between a parent and a child comes from the first time you leave him home alone. Although different children will react in different ways, there are ways to tell whether your child may be ready to take on the head of the house role -- temporarily, at least.
Start by leaving him for short durations. Run to the store to grab groceries, for example, and see how you and he handle it. If he remains calm and collected, he'll probably soon be ready to stay alone for longer periods.
If you decide it's OK to give him the evening to himself, be sure to call and check in often and provide him with a phone number to reach you. You'll also want to ensure your child has access to neighbors or close relatives in case you can't be reached -- or in case you want someone to drop by to check on him. The first time you leave him home alone, you'll want to run through a few safety measures, such as who to call in case of an emergency, what to do in case of a fire, and which appliances are off-limits.
Make sure he understands that you're still ruling the house by proxy. This means all the same considerations of TV watching, computer usage, video game playing and eating are all set in stone. If these rules and boundaries are breached, make him understand there will be consequences.