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Treat Your Windows to Energy Savings

Energy-Efficient Windows: The Basics

Our Buyer’s Guide helps you understand how energy efficient windows work including the terms and definitions you need to know. When replacing older windows, we strongly recommended that you upgrade to double-paned glass. Other features to consider: gas filling, low-e coating and window systems with combined low U-factors (0.35 or less for California’s climate) and low solar heat gain coefficients (0.3 or less for California).

Windows of Opportunity

Windows make up 10% to 30% of wall space and are some of the most visible elements of your home. Windows are also the most vulnerable part of your home’s exterior, accounting for 30% of heat loss or gain.1


To Upgrade or Not to Upgrade…

Upgrading windows can be expensive, and window replacement generally doesn’t have a quick financial payback in terms of energy savings. Insulation and weatherization are usually more cost-effective solutions. Unless a window is broken or in poor condition, investing in other upgrades around the home can help you save more on your energy bills than new windows. You also have a number of options to enhance your existing windows.

Window Treatments

If your windows are in good condition, cut down on heat flow with insulating blinds, shades, or curtains. In most cases, these can be installed fairly easily. Keep your window coverings closed during the day in summer and at night in winter to decrease heat flow. Some good options include: honeycomb shades and quilted shades (these often have a higher R-value, offering better insulating properties).

Fixer Uppers: Older Windows

If your windows are worn or old, consider replacing specific parts of the fixtures or whole windows.

  • Spruce up the sash. Replace the sash (the movable portion of the window with the glass) if the window frame is still in good condition, or has historic or aesthetic value. Replacement upgrades include low-e glass and tilting models that allow easy cleaning, and typically cost between $250 to $400 per window.2 
  • Add an insert. If the frame is in good condition, remove the existing sash and install an insert window. The pocket replacement may decrease the window area, but this option provides a wide variety of sash materials to choose from. This option can cost a few hundred to over a thousand dollars per window; so consult a professional for details.
  • Replace that window. If the whole window assembly is in poor condition, or if you’re installing a different size than the old window, replace it with a new, high-efficiency model. Completely replacing your window can typically cost $400 to $800, plus installation costs.3


One of the most advanced windows available are called “superwindows.” These sophisticated systems are very efficient and good options for extremely hot or cold climates. Superwindows can help save on heating and cooling energy, because they allow you to downsize or even eliminate cooling or heating systems. Currently, superwindows are more expensive to install than the most advanced double-paned windows.4 Weigh your heating or cooling demands before choosing superwindows, to determine their cost effectiveness.

Use & Care

Properly installing and maintaining your home’s windows will maximize efficiency measures. Learn more about Window Use & Care, where to start, and how to care for windows and treatments for the most savings. Return to Building and Materials.

Buyer’s Guide

Before you shop for efficiency upgrades, visit the Window Buyer’s Guide for easy facts and figures that can help you choose the best materials for your home, needs and budget.

1 Archambault, T., Wang, K., & Yardi, R. (2004). Home Energy Briefs, #1 Building Envelope. Snowmass, CO: Rocky Mountain Institute.rmi.org.
2 Archambault, T., Wang, K., & Yardi, R. (2004). Home Energy Briefs, #1 Building Envelope. Snowmass, CO: Rocky Mountain Institute.rmi.org.
3 Windows Connect.(2012). Casement Window Prices. Retrieved October 1, 2012 from replacementwindowsconnect.com
4 Archambault, T., Wang, K., & Yardi, R. (2004). Home Energy Briefs, #1 Building Envelope. Snowmass, CO: Rocky Mountain Institute.rmi.org.

This program is funded by California utility customers and administered by Southern California Edison under the auspices of the California Public Utilities Commission.

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