Ask the Energy Expert

As an energy expert, I’ve been getting more questions lately from customers trying to balance two things at once: staying comfortable in the heat and keeping energy costs in check. Here’s a question that’s been coming up often:

“Can an A/C window unit help me stay cool and manage my energy costs, or is there a better option?”

Short answer: it can, but only if it’s used the right way. For some homes, there’s a better option.

Window A/C units are designed to cool one room, not the whole house. That’s why they can work well for bedrooms, home offices or small apartments. But they’re also easy to misuse, which is where comfort can slip, and energy costs can rise.

Where window A/C units fall short

One of the biggest issues is size. I see this all the time.

An oversized unit cools the room fast, then shuts off before pulling out enough humidity. The room feels cool, but still sticky. An undersized unit runs nonstop and never quite catches up.

Air leaks don’t help either. Gaps around the unit let hot air sneak in and cool air escape, forcing the unit to work harder than it should.

And remember, window units only cool the room they’re in. Running one when no one’s there doesn’t improve comfort and just adds to your energy use.

A smarter option for many homes without central air

If you rely on window units regularly, or use more than one, this is where ductless mini-split systems are worth a look.

Mini-split systems cool specific zones, so you’re not paying to cool rooms you’re not using. They’re typically more efficient than window units, run quieter and give you more control over comfort.

They also skip ductwork altogether, which helps avoid the energy losses that can come with traditional systems.

Some high-efficiency mini-split systems may qualify for an instant rebate when installed by a participating independent contractor, which can help offset the upfront cost.

But what about price?

Mini-splits do have a higher upfront cost than A/C window units. But they can provide more consistent comfort and efficient cooling over time.

If you only cool one room occasionally, a window unit may still make sense. If you’re cooling multiple rooms or running window units daily, a mini-split system can be a more efficient long-term option.

How to get more out of a window A/C

If a window unit is the right choice for your home right now, a few simple moves can make a big difference:

• Make sure the unit is the right size for the room.
• Seal gaps around the unit with weatherstripping or foam.
• Use energy-saving mode if your unit has one.
• Turn it off when you leave the room.
• Keep doors closed so cool air stays where you need it.

Bottom line

A/C window units can be a practical way to stay cool in a single space. But if you’re cooling multiple rooms or using them often, a mini-split system may offer better comfort and efficiency over time.