Do New Windows Lower Energy Bills? What the Data Says

The Short Answer

New windows do lower energy bills, but usually by less than the sales pitch suggests, and they are one of the most expensive ways to get the saving. ENERGY STAR says certified windows lower household energy bills by an average of up to 13 percent nationwide when replacing single-pane windows. If your current windows are already double-pane, the gain is smaller.

If the goal is a lower bill rather than new windows for their own sake, low-e storm windows and air sealing get much of the same benefit for a fraction of the cost.

How Much Windows Matter

Windows are a big part of the envelope. South Carolina’s state energy office, echoing the Department of Energy, says windows are responsible for 25–30 percent of residential heating and cooling energy use. That is heat moving through the glass and frame, sun coming in, and air leaking around the sash.

But heating and cooling is only part of your bill, and replacing windows does not remove that share; it reduces it. That is how a large-sounding share becomes a saving of around 13% even in the best case of replacing single-pane glass.

The Payback Problem

Replacement windows are expensive, so the payback on energy alone is long. Martin Holladay, writing in the Journal of Light Construction, put it this way: window replacement is almost never cost-effective, and the payback period can be as long as 20 or 30 years.

There are good reasons to replace windows: rot, broken seals, windows that will not open or lock, noise, or a renovation already under way. Just count the energy saving as a bonus rather than the reason.

Tax credit: the federal Energy Efficient Home Improvement Credit applied only to improvements made through December 31, 2025. Window quotes in 2026 should not deduct it. Check state and utility programs instead.

Cheaper Options That Work

Low-e storm windows. These fit inside or outside your existing windows. The Department of Energy says they can save you 10%–30% on heating and cooling costs, with similar savings to full replacement at about one-third the cost. ENERGY STAR now certifies storm windows and says certified ones pay back the incremental cost in about three years.
Air sealing and weatherstripping. Caulk the gaps around the trim and weatherstrip the sashes. This is the cheapest window fix and helps whether you replace them or not.
Interior film kits for the worst windows in winter. ENERGY STAR says these are inexpensive, reduce drafts, help the house feel warmer during winter months.
Window coverings. Cellular shades and lined drapes cut heat loss at night and heat gain in summer. See our window treatments guide.

If You Do Replace: Read the Label

Every rated window carries an NFRC label. The three numbers that matter for energy:

U-factor. The NFRC says it measures how well a product can keep heat from escaping from the inside of a room. Lower is better.
Solar Heat Gain Coefficient (SHGC). How well the window resists unwanted heat from the sun. Lower is better in hot climates; in cold climates a higher SHGC on south-facing windows can help.
Air leakage. How much air comes through the product itself. Lower is better.

ENERGY STAR sets U-factor and SHGC limits by climate zone, so a window certified for your zone is a sensible minimum. Installation matters as much as the window: insist that the gap between the new frame and the opening is air sealed.

What We’d Buy for Now

We may earn a commission if you buy through these links, at no extra cost to you. Products are chosen on published specifications; we do not test them in-house (how we choose).

3M Indoor Window Insulator Kit

Shrink film for the draftiest windows this winter while you decide on storms or replacement.

Check price on Amazon

Frost King V443/4 Vinyl Foam Tape (4-pack)

For sashes that do not close tightly. Seal only the parts that open and close.

Check price on Amazon

Free: Home Energy Audit Checklist (PDF)

A two-page, room-by-room checklist for finding air leaks, standby power and heating and cooling waste yourself, in the order that pays back fastest. Get it now, plus new fix guides by email. Unsubscribe any time.

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Frequently Asked Questions

How much do new windows save on energy bills?

ENERGY STAR says certified windows lower household energy bills by an average of up to 13% nationwide when replacing single-pane windows. Replacing double-pane windows saves less.

Are replacement windows worth it for energy savings alone?

Rarely. Payback on energy alone is often measured in decades. Replace windows for rot, failure, noise or comfort, and treat the energy saving as a bonus.

What is a cheaper alternative to replacing windows?

Low-e storm windows. The Department of Energy says they can save 10% to 30% on heating and cooling at about one-third the cost of replacement, and ENERGY STAR says certified storm windows pay back in about three years.

Is there a tax credit for new windows in 2026?

No. The federal Energy Efficient Home Improvement Credit covered improvements made through December 31, 2025. Check state and utility programs.

What window ratings should I look for?

A low U-factor, an SHGC suited to your climate and low air leakage on the NFRC label, and ENERGY STAR certification for your climate zone.

Related Guides

Window treatments and energy savings — coverings that help
Drafty rooms checklist — seal before you spend
How to find thermal leaks — is it the windows at all?
Energy audit cost — a test before a big purchase
Best window insulation kits — the $2-a-window alternative