The ideal household temperature for a middle aged healthy adult is between 68 and 72 degrees F. If you are looking to save on heating costs, as low as 62 degrees F may be tolerable as long as you are dressed appropriately in layers. This does not mean a jacket is required but a shirt and sweater.
The "ideal" temperature is whatever temperature feels most comfortable to you. Some people prefer warmer temperatures, and others prefer colder. Personally, I keep my thermostat set at around 70-72 degrees.