Get an Estimate

Energy-Efficient Windows: Complete Guide for 2023

There’s nothing better than letting the sunshine into your home on a beautiful day. Well, until you get your monthly…
Author Image
Jacob Wadding

There’s nothing better than letting the sunshine into your home on a beautiful day. Well, until you get your monthly energy bill, that is.

Some of the best features of windows, like connecting you to the outdoors, offering ventilation, and letting in natural light, can all, unfortunately, spike your utility bills if you don’t have an energy-efficient system. If you’re due for a window replacement soon, energy-efficient windows are well worth the investment.

Let’s explore everything you need to know about energy-efficient windows as a homeowner, including:

  • Average costs
  • Energy performance factors
  • Energy efficiency labels
  • Energy performance in different orientations
kitchen with energy-efficient windows

Average Costs of Energy-Efficient Windows

Energy-efficient windows will almost always cost more than their non-efficient counterparts. So, it’s easy to wonder if the investment is worth it and if energy-efficient windows actually save you money in the long run.

At ARCH Exteriors, we’re open and honest about our pricing because we believe that every home and business owner deserves energy efficiency at an accessible price. You can find our full pricing guide here.

You’ll see that the cost of window installation ranges from $525 to $1,800 per window. You’ll get basic levels of energy efficiency on the lower end and premium performance on the most expensive end.

Most homeowners find great energy performance in the mid-range, which allows for a fantastic return on investment (ROI) because the window features will help lower utility bills. (You can expect to see an average savings of 12-20% on your energy costs!)

Heat Conduction Factors 

Windows are graded on how much heat they gain or lose through the glass. These heat conduction grades fall under the following four categories, which, when added all together, determine a window’s level of energy efficiency:

1) U-Factor

U-factor for windows is the rate at which the window conducts heat flow. The U-factor number only applies to the glass or glazing. This rating system was established by the National Fenestration Rating Council (NFRC)— a non-profit group that offers a consistent, independent rating system for the energy efficiency of components like:

  • Windows
  • Doors
  • Skylights
  • Attachment products

You want to look for a low U-factor (0.30 or lower), as this represents windows with great resistance to heat flow and the best insulating qualities. A higher U-factor indicates less-efficient windows with poor insulating abilities.

bedroom with energy-efficient windows and skylight

2) Solar Heat Gain Coefficient (SHGC)

Solar heat gain coefficient (SHGC) is a grade that refers to the solar radiation allowed to come through the window. The window may absorb or transmit the solar heat that comes through and then release it as interior heat in your home.

Higher SHGC ratings (0.30 to 0.60) indicate that a window will effectively collect heat during colder months. But a lower rating (0.40) symbolizes that the window would be better for keeping cooling costs low during hot summer months. Choosing this rating should depend on your region and the type of weather you more commonly experience.

3) Air Leakage Rate

The air leakage rate indicates how much outside air is seeping through the window unit. This measurement is determined before the window is installed, and it reflects the presence of a specific pressure difference. The lower a window’s air leakage rating (0.3 and below), the better airtightness and energy performance it has.

4) Sunlight Transmittance

Sunlight transmittance is the ability of the window glazing to transmit sunlight into the home. There are two components of sunlight transmittance for windows: visible transmittance (VT) and light-to-solar gain (LSG).

  • Visible Transmittance: VT is expressed as a number between 0 and 1, and this number indicates how much of the visible spectrum of sunlight is transmitted compared to the sensitivity of human eyes. A higher number transmits more visible light. Use this rating to help determine what windows you should get if you need certain daylight requirements or reduced interior glare.
  • Light-to-Solar Gain: LSG is the ratio between the visible transmittance and solar heat gain coefficient. It provides a gauge of the anticipated efficiency of different types of glass or glazing as they transmit daylight but block heat gains. This rating isn’t always provided on windows, but if it is, a higher number indicates more light transmitted without adding excessive heat.
sunlight shining through energy-efficient windows

Energy Efficiency Labels: What They Mean

You can’t just trust that a random window brand without an energy label is energy-efficient just because Joe Schmo says so. Windows need to go through a rating process by independent organizations with pre-set standards to be labeled as energy-efficient. The two most common and reputable labels you’ll see are ENERGY STAR and NFRC (National Fenestration Rating Council).


ENERGY STAR is a voluntary program with strict energy efficiency criteria set by the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy. This government-backed symbol for energy efficiency provides credible and unbiased information for home and business owners to make well-informed decisions.

The program has been in place since 1992, and every dollar the EPA spent on ENERGY STAR resulted in $350 in energy cost savings for American households. ENERGY STAR has been a critical tool in helping fight climate change, improving air quality, and protecting public health for years.

Seeing an ENERGY STAR approval rating on your windows ensures the window has passed the stringent criteria set by the federal government.

NFRC Energy-Rated Windows

The second label you’ll commonly see is the NFRC label, which is comprised of the four heat conduction components we dove into earlier. While an ENERGY STAR label will tell you if a product is energy-efficient, the NFRC label helps you compare between products by breaking down each specific energy performance.

You can compare the ratings in each of the four categories:

  • U-factor
  • Solar heat gain coefficient
  • Air leakage
  • Sunlight transmittance

Depending on your region and specific needs, you can use these four categories within the NFRC label to decipher the ideal window for your home or business.

How Orientation & Direction Affects Energy Performance 🧭

When you consider upgrading to new energy-efficient windows, you’ll consider the ratings and labels, price range, and your individual needs. But you should also factor in the orientation of the windows (AKA the direction they face) in your house. Windows facing north, south, east, or west may all get different levels of sun exposure or shade, and they should be taken into consideration as you make this investment.

South Facing Windows ⬇️

In primarily colder climates, windows with higher glazing should be installed on the south-facing side of your home. This positioning allows the windows to absorb more solar heat during cold days when the sun is positioned lower in the sky.

However, to keep heat gain at a reasonable level in the summer months in these regions, use overhangs and awnings.

South-facing windows in colder climates will be most efficient with the following ratings:

  • SHGC over 0.6 to maximize heat gain through solar absorption during winter
  • U-factor 0.35 or lower to decrease the conductive heat transfer
  • VT rated high to let a high rate of sunlight into the home

Opt for a lower SHGC rating for south-facing windows in hotter climates to reduce cooling costs.

construction worker installing energy-efficient windows

North Facing Windows ⬆️

North-facing windows in cooler climates don’t collect much solar heat, so they’re primarily used for natural lighting. Look for low-emissivity (low-E) window glazing if you live in a colder climate. This will help control the gain and loss of solar heat in cold temperatures.

In warmer climates, once again, opt for a lower SHGC rating for your north-facing windows to keep cooling costs down.

East and West Facing Windows ⬅️ ➡️

Windows on the east and west sides receive heat and light, but they’re harder to shade from the summer sun. While east-facing windows let in the morning sunshine and keep away nighttime chilled temperatures, west-facing windows are almost never energy superstars.

West-facing windows can let in a lot of heat on summer afternoons when the sun is high. Opt for glass with a low SHGC rating because this built-in shading will reduce the amount of solar energy that seeps in. An awning that slopes over the top two-thirds of an east or west window can reduce heat gain significantly— up to 77%! You can remove these awnings in the winter to let more sun back in.

A High-Quality Installation Makes All the Difference

Even the highest-rated energy-efficient windows in the world would be useless without a proper installation. Faulty installation methods can completely void the energy performance of a window, so it’s paramount to choose a top-rated and trusted local window installation team.

At ARCH Exteriors, we are proud to install ENERGY STAR-certified ProVia Endure vinyl windows with impressive energy performance. Our expert installation team will ensure your new windows will not only look beautiful but save you money on energy costs as well.

Contact us today to learn more about how we can help with your upcoming window replacement. Plus, ask about our lifetime transferable warranty on ProVia windows!

About the Author
Your home is probably the most expensive thing you own. When you hire somebody to make improvements, you want high-quality work. In addition, you hope they’ll take the same care you would. You want someone with a good reputation, legitimate credentials, well established, using quality materials, and who charges a fair price. For over 11 years, I have worked hard to provide all of those benefits to my clients. One of the major reasons we have been able to do that is our ability to keep highly qualified personnel. Our workers are well trained, properly motivated, and managed professionally. I make certain that I convey measurable systems and procedures that our team understands and can readily follow.

Quit Wasting time and money with
terrible home contractors

Here at ARCH, You Work With The Best