The window salesman isn’t lying about one thing: Your windows really are costing you money.

According to the Energy Department, heat moving in and out through windows accounts for 25% to 30% of the energy a typical home uses for heating and cooling. That’s real money going straight through the glass.

Where the pitch goes off the rails is the fix. Energy Star puts new energy-efficient windows at about $400 to $1,500 or more apiece, installed. For a home with 10 windows, that’s $4,000 to $15,000 or more. That’s a used car. For many homeowners, it’s also overkill.

There’s a cheaper option a replacement-window salesman has little reason to push: the low-e storm window. Here’s what I’d do before signing anything, in the order I’d do it.

1. Caulk and weatherstrip first

Before you spend a dime on glass, stop the air that’s sneaking around it. A drafty window is often a leaky frame, not a bad pane.

The Energy Department says caulking can cut your heating bill by as much as 20%, and the job usually takes an hour or two. Weatherstripping takes about an hour and can trim your energy use by up to 10%.

All it takes is a caulk gun, a few tubes and a roll of weatherstripping from the hardware store. Do it on a dry day, and you’ll feel the difference the first time the wind kicks up.

While you’re at it, go after the other small drains in your house, starting with the energy vampires that can cost you up to $200 a year.

2. Know what a low-e storm window is

Forget the rattling aluminum storm windows your grandparents wrestled into place every fall. The modern version is a different animal.

A storm window is a second pane that attaches to the window you already have, inside or out.

The newer ones carry a low-emissivity, or low-e, coating — a thin coating that cuts down on heat moving through the glass. They come in fixed models and in ones you can open.

The pitch is simple: You keep your existing windows and give them a second coat of armor. Energy Star adds a side benefit: They can also cut down on outside noise.

How much can they save? It depends on whose numbers you read, so here they are, separately. The Energy Department says low-e storms can cut annual heating and cooling costs by 12% to 33% compared with having no storms at all.

The EPA’s estimate is lower. Its Energy Star program says certified low-e storms save about $350 a year on average, roughly 10%, when they’re added to single-pane windows with clear glass. The agency calls that figure conservative, and notes it leaves out savings from plugging leaks around old windows.

3. Run the per-window math

This is where the window salesman’s pitch falls apart. Let’s do the numbers.

A Department of Energy playbook prepared with the Pacific Northwest National Laboratory pegged a new low-e storm window at about $10 a square foot in 2023. For a standard 3-by-5-foot window, that’s about $150.

Energy Star puts an energy-efficient replacement window, installed, at about $400 at the low end and about $1,500 or more at the high end. Per window.

Now picture a house with 10 windows and a $1,000 annual heating and cooling bill.

Storms: 10 times $150 is $1,500 at 2023 prices. The playbook doesn’t say whether that includes installation, but many interior storms are a do-it-yourself job. Replacements: $4,000 at the low end and $15,000 or more at the top.

The Energy Department says storms deliver savings similar to a full replacement. So let’s give both options the same benefit: $200 a year, which is 20% of that bill, well inside the agency’s 12%-to-33% range.

The storms pay for themselves in about 7½ years. The cheapest replacements need 20 years. The pricey ones need 75. You may well have moved, or worse, before those break even.

Have a bigger bill or a colder climate? Bigger savings mean the storms pay off even faster.

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4. Decide: Inside or outside

Storm windows mount on either side of your existing window, and the choice matters.

Interior storms are generally the easier install, according to the Energy Department playbook, especially upstairs, because you usually don’t need a ladder or scaffolding. Many are built so a handy homeowner can put them in without a contractor.

If you own a condo and can’t touch the outside of the building, interior storms may be your only option.

The trade-off: An interior storm does nothing to shield your existing window from rain, sun and wind.

Exterior storms do. Modern ones stay up all year and are chosen to work the same way your current window opens, so you aren’t swapping panels every spring and fall.

My rule of thumb: If the outside of your windows is weathered and you want to protect it, go exterior. If you’ve got second-floor windows and no appetite for ladders, go interior.

5. Forget the tax credit — call your utility instead

If a salesman tells you Uncle Sam will chip in, he’s behind the times.

The federal energy-efficient home improvement credit used to cover 30% of the cost of qualifying windows, up to $600. It’s gone. The IRS says the credit doesn’t apply to anything placed in service after Dec. 31, 2025.

Losing a $600 sweetener makes a $15,000 window job look even worse — and makes a $1,500 storm-window project look even better.

Your best shot at help now is local. Plug your ZIP code into Energy Star’s Rebate Finder, which lists storm windows as a category.

Then call your electric or gas utility and ask directly. What’s offered varies from one utility to the next, so don’t assume a database has the last word.

6. Know when replacement really is worth it

I’m not saying never replace a window. Sometimes it’s the right call, and storms are a bandage on a broken leg.

Energy Star lists the red flags. Windows with degraded sills and sashes can let water seep into your walls, which turns a window problem into a bigger one. Windows that won’t open or have been painted shut are another sign.

My own test is simpler: If you can push a screwdriver into soft, rotted wood around the frame, a storm window won’t save it. Replace it.

Single-pane glass is on Energy Star’s replacement list, too. But that’s exactly the kind of window the EPA’s $350 storm-window estimate assumes. If the frames are sound, storms are still worth pricing first.

If your house was built before 1978, Energy Star notes that anyone replacing the original windows should follow lead-paint safety rules. Ask about it before the crew shows up.

And when big repairs do pile up, it pays to have a plan. Here are six ways to keep home repair costs down.

The bottom line

Windows leak money. That part of the sales pitch is true.

But the cure doesn’t have to cost thousands. Seal the leaks for the price of a few tubes of caulk.

Price storm windows (roughly $150 apiece at 2023 prices) before you price replacements at $400 to $1,500 or more. Check for local rebates. Save replacement for windows that are truly shot.

Then go after another big energy hog in your house. Your water heater can cost up to $600 a year, and a few simple changes can chill that bill, too.