More than half of the energy used in your home goes to heating and cooling. Replacement of HVAC will probably have one of the biggest impacts on overall energy efficiency in your home. First, properly maintain your HVAC system: change your filters, clean your ducts regularly, and hire a professional to inspect your system to make sure it is running effectively.

Immediately replace these with a high-efficiency furnace, air conditioner, or heat pump. Other upgrades that pay off are smart thermostats.