Weather plays the biggest role in the amount of energy that gets used, and is one of the biggest impacts on energy bills. Bill-payers typically see their highest bills after the hottest and coldest months.
If you are paying the bills for your property, conserving energy will drastically increase the potential for savings. You may also find that you will face fewer maintenance issues, since older appliances are more likely to act up. Even if it is your tenants who pay the energy bills, making eco-friendly improvements will increase the overall value of your property. There is now a huge move to become more energy efficient, so new upgrades make a property more attractive to potential buyers.