One homeowner's brutal electric bill has them eyeing the vents in unused bedrooms. The main question is: If the vents in those unused rooms are shut, will the bill drop?

Commenters in an HVAC Reddit thread said the money-saving idea may end up doing the opposite.

Here's what to know

In a Reddit thread, the homeowner with central air in a 2,200-square-foot house said: "My electrical bill gave me cardiac arrest."

Wanting to lower the bill, the homeowner asked: "If I close vents (and the doors to the rooms with closed vents), can I save electricity?" 

Replies largely agreed that closing vents and shutting doors in unused rooms is usually not a good way to reduce air-conditioning costs. They concluded that the system would still do nearly the same amount of work. 

Later in the discussion, one commenter wrote: "It really doesn't save much and those rooms become a heat load in the residence. It does mess with air flow velocities and volumes."

If high cooling bills are the bigger issue, upgrading your heating and cooling system is one of the best ways to save money on utility bills and protect yourself against rising energy prices. Palmetto can help homeowners understand their HVAC options and slash their energy bills with new, efficient HVACs and heat pumps, and Palmetto's Comfort Plan network can help connect you with vetted installers and efficient solutions for your home.

More background

Closing registers sounds logical because it seems like a way to avoid cooling rooms you are not using. However, several commenters said the real-world effect can be the opposite, especially if multiple vents are closed.

Longer run times were one concern raised in the thread.

One commenter said: "The air conditioner and ductwork is designed for a specific amount of airflow." Reducing that flow can raise pressure, hurt efficiency, and delay reaching the thermostat setting.

Another commenter added: "Actually will use more because it will take longer to satisfy the thermostat." Even worse, if airflow is reduced too much, the coils can get excessively cold, frost may start to form, and the system can eventually freeze up.

What can be done?

Instead of closing off rooms, commenters pointed to steps such as sealing air leaks, improving insulation, and bumping the thermostat up a few degrees.

"Easiest way to lower your bill is put in more insulation," one person commented.

For bigger savings, it may be worth exploring a more efficient system altogether. Palmetto notes that if you're not ready to spend upfront, the Comfort Plan includes $0-down options that can lower your heating and cooling costs by up to 50%, and Palmetto Comfort Plans include 12 years of free maintenance. More information is available here.

Homeowners can also pair solar panels with electric appliances, including efficient HVACs and heat pumps, to drive utility costs even lower. EnergySage makes it easy to find the best solar system and installer for your home and budget, saving you up to $10,000 on installations.

The original poster considered solar as another way to lower bills and commented: "Thanks for the detailed response! … It would really be nice to get some solar incentives going again."

Where can I learn more?

The articles here tackle similar HVAC questions. They cover practical ways to save energy, from thermostat tweaks and smart controls to routine air-conditioning maintenance.

• Homeowners are trying a simple HVAC vent trick to cut bills without choking airflow.

• HVAC technicians say smarter thermostat settings during trips can trim cooling costs.

• Homeowners can keep systems efficient by cleaning AC drains before clogs drive up costs.

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