How to Choose Energy-Efficient Windows

Improving a home’s energy efficiency is one of the top reasons homeowners choose to replace or update old windows. Energy-efficient windows not only make your home more comfortable year-round, but they can also help cut down on utilities, saving both energy and money.

Heat gain and heat loss through windows account for 25–30% of residential heating and cooling energy use, according to the U.S. Department of Energy. That makes replacement windows one of the most impactful upgrades homeowners can make to improve efficiency and comfort.

By using energy-efficient windows, your home will be positively impacted. Explore the three ways these windows can benefit you in the long term.

• Cost savings: Reduce your energy bill with better insulation. Energy-efficient windows help lower heat loss and gain.
• Increased comfort: Stable temperatures call for less HVAC use. Windows that prioritize energy efficiency reduce drafts and leaks in your home.
• Environmental impact: Lower your carbon footprint by reducing your overall energy consumption. ENERGY STAR® certified windows may also qualify for a 30% federal tax credit up to $600 through 2032, helping offset your investment.

When shopping for energy-efficient new or replacement windows, keep these six things in mind:

The style of window you choose has a direct impact on energy efficiency. 

Picture windows are the most energy-efficient type of window because they do not open and form a permanent airtight seal. They’re a great choice for spaces where natural light and outdoor views matter most. 

Among operable styles, casement and awning windows typically seal tighter than double-hung windows because the sash presses firmly against the frame when locked. This tighter compression seal helps reduce drafts and air leakage. 

While fixed and hinged window styles often offer stronger thermal performance, it’s important to balance efficiency with ventilation needs and how each room functions.

A key component of any window is its glass. The right window glass option, optimized for your climate, can help reduce heating and cooling costs by slowing thermal transfer. 

With dual-pane or triple-pane glass, inert argon gas can be used between panes of glass to improve insulating properties. Laminated, tempered, tinted and obscure insulating glass can also add ultraviolet protection. 

For homes with south- and west-facing windows, Low-E glass coatings can be especially important because these elevations receive the strongest sun exposure. The right coating helps reduce solar heat gain while still allowing in natural light. 

In addition to energy-efficient glass, keeping curtains, shades and blinds open on sunny winter days is another way to improve window energy savings.

Proper window installation plays a major role in how well new windows perform over time. Even the highest-quality window can underperform if it is not properly installed and sealed. Gaps around the frame, improper flashing or poor sealing can lead to air infiltration, drafts and even moisture intrusion that may cause costly water damage over time. 

A tightly sealed and properly installed window helps reduce unwanted air leaks, minimize heat loss and improve overall comfort throughout the home. Just as importantly, professional installation helps ensure the window performs as designed for energy efficiency, operation and long-term durability. 

For many homeowners, professional installation can also provide added peace of mind through installation workmanship coverage. When replacement windows are purchased and installed through a local Pella showroom, for instance, the project may also include a 10-year installation warranty and service agreement, adding another layer of protection beyond the product warranty itself.

The direction your windows face can influence which glass features deliver the most comfort and efficiency. Understanding sun exposure by orientation helps homeowners prioritize where solar-control glass coatings may have the greatest impact. 

South- and west-facing windows typically receive the strongest afternoon sun and the highest solar heat gain, making these areas the top priority for solar-control Low-E glass coatings. These coatings help reduce excess summer heat while still allowing natural light into the home. 

North-facing windows receive the least direct sunlight throughout the day, so the focus is often less on solar heat gain and more about maintaining year-round insulation. In these areas, standard Low-E coatings paired with dual- or triple-pane glass can help improve thermal performance and indoor comfort. 

East-facing windows receive direct morning sun, which is usually less intense than afternoon western exposure but can still contribute to warming bedrooms, kitchens and breakfast areas early in the day. Low-E glass can help moderate this heat gain while preserving bright morning light. 

Taking sun exposure into account can help homeowners make more strategic glass decisions, especially when replacing only part of the home or prioritizing rooms that feel hottest during summer afternoons.

Your home’s geographic location and climate help determine the best energy-efficient windows for your region. 

Depending on your climate, prioritize lower U-Factor values for cold regions and lower SHGC values for hot, sunny climates. Choosing windows specifically rated for your climate zone helps maximize performance and long-term savings.

Your choice of window frame material influences your window’s overall energy efficiency.

• Wood windows provide excellent insulation.
• Fiberglass windows offer insulating properties similar to wood.
• Vinyl windows with multi-chambered frames reduce heat loss through insulating air pockets.

To choose energy-efficient windows with confidence, it’s important to understand the key metrics used to rate their performance. You can usually find this information directly on the window label, which makes it easier to compare options side by side while shopping. 

Look for products that feature the ENERGY STAR® label, which means the window has met strict energy efficiency standards. These windows are also tested and rated by the NFRC.

Replacing single-pane windows with ENERGY STAR® certified windows can help homeowners reduce annual heating and cooling costs by 12% on average.

NFRC Energy-Rated Windows 

The NFRC label provides several energy ratings that can help you compare window options: 

• U-Factor: Measures insulation performance. Lower numbers mean less heat transfer.
• SHGC: Indicates how much solar heat enters through the glass.
• Visible Transmittance: Shows how much natural light enters the home.
• Air Leakage: Lower values mean fewer drafts.
• Condensation Resistance: Higher numbers indicate better moisture resistance.

For cold climates, a U-Factor of 0.25 or lower is ideal. In moderate climates, 0.30 or lower is generally recommended. 

The right product choices and installation approach can make a noticeable difference in how well your new windows perform over time. Use the tips below to help improve comfort, reduce drafts and support long-term energy savings throughout your home.

Window performance needs can vary by region, so selecting glass packages and frame materials designed for your local climate can help improve year-round comfort and support lower heating and cooling costs.

These elevations typically receive the strongest sun exposure and highest solar heat gain, making upgraded glass features especially valuable for reducing summer heat buildup while maintaining natural light.

Even high-quality, energy-efficient windows can underperform if they are not properly installed and sealed, so professional installation is essential for preventing air leaks and preserving long-term performance.

Whole-home replacement can help create more consistent insulation throughout the house while also reducing repeated labor setup costs that may come with phased projects.

ENERGY STAR® certified windows are independently verified for energy performance and may also help eligible homeowners take advantage of available tax incentives, improving the long-term value of the investment.