Suppose we have a body (cube or sphere) at temperature T1. The surrounding area has a constant temperature T2 with T2<T1. We need to deliver the body at temperature T1 at some time in the future. There are two options: We can heat the body continuously at temperature T1 or we can allow the body to cool down and then turn on the heating in order to deliver the body at temperature T1 when this is required. I know that the 2nd option of the most energy saving. I would need a quantitative analysis on this or if you give me a reference.