King Charles III (77) and his son Prince William (44) could soon fly a million-dollar bill into the house: Due to increased energy standards for rental apartments, the two royals face costs of more than 11.6 million euros. This is evident from an investigation by The Guardian. The newspaper evaluated more than 700 energy certificates of real estate of the Duchy of Cornwall, the Duchy of Lancaster and the Sandringham estate. The result: 630 prope…