The best way to get a concrete answer on this question on whether a central a room air conditioner would be more efficient in your home is to get an in-home energy audit from a certified energy auditor in your area who can analyze the structure of your home along with your current cooling and heating appliances, ductwork, insulation levels, etc. With any energy efficiency question, there are usually several factors at play.

In general, if your current air conditioning unit is inefficient and you’re willing to invest in a highly efficient central air conditioner, than there is a good chance that you could save money on your utility bills in the long run. The upfront cost of replacing your room AC with a central AC with a high Seasonal Energy Efficiency Ratio (SEER) will be somewhat expensive compared to just buying another window AC. However, if you plan to live in your home for many more years, you should have time to recoup the extra cost through savings on your utility bills.

There are couple incentives for residents in the Philadelphia who are interested in installing an ENERGY STAR rated central air conditioner. The Keystone HELP Energy Efficiency Loan Program offers low interest loans of up to $35,000 for qualifying improvements, but to qualify, your household income cannot exceed $150,000.

Also, the federal government offers the Residential Energy Efficiency Tax Credit, which will cover up to 30 percent of the cost of you new AC through a tax credit, not to exceed $1,500. This credit includes labor costs, but to qualify, you’ll need to buy a system (split) with a SEER 16 rating or higher.