When installing a new furnace, it's important to consider certain factors when selecting a new unit. These can include: Fuel source: It's important to determine what type of fuel you want your new unit to use. Gas, oil and electric systems can have varying impacts on your home and your lifestyle so it's important to be aware of these before you choose a unit. Size: It's crucial to know what size of furnace you need for your home or property. If it's too small, it will cause your utility bills to increase and can lead to wear and tear on the unit. If it's too large, it can have to adjust to maintain the desired temperature in your property. Energy-efficiency: Consider how energy-efficient you want your unit to be. The more energy-efficient a unit is, the more it might cost upfront, but the more it will save you in energy costs later. Required maintenance: Before you buy a unit, make sure you know what maintenance you will need to perform on the system.