maintaining a temperature difference between the house and the outside when there is no need to do so costs money and power. (nobody is home so comfort isn't an issue, pets and equipment are able to deal with different temperature ranges than we consider comfortable)
Insulation and heat pumps don't change this basic fact.
Insulation changes the rate at which the inside equalizes temps with the outside, and therefor the amount of heating cooling needed to maintain the temp difference. Heat pumps are relatively efficient tools to maintain the temp difference (at least under most conditions), so they reduce the cost.
but by far the most efficient thing to do is to not maintain the temp difference when it's not needed.