Awning Energy Savings: How Much Can Shading Cut Your Cooling Load?
Quick answer
The U.S. Department of Energy says awnings can reduce summer solar heat gain by up to 65% on south-facing windows and up to 77% on west-facing windows. In dollars, the savings for a typical home are usually modest, often tens to low hundreds of dollars a year, but the drop in peak afternoon heat gain through west glass makes rooms noticeably more comfortable.
Awnings save energy by stopping sunlight before it passes through glass. According to the U.S. Department of Energy's Energy Saver guidance, awnings can reduce solar heat gain in summer by up to 65% on south-facing windows and up to 77% on west-facing windows. For most homes, that translates into modest annual dollar savings, often tens to low hundreds of dollars depending on climate, glass area and electricity rates, plus a larger and more noticeable cut in peak afternoon heat that makes west-facing rooms more comfortable.
This page explains why shading outside the glass works better than inside, how orientation changes the result, and how to estimate your own savings with stated assumptions. If you are weighing the whole purchase, are awnings worth it? covers comfort and other value, and the awning cost calculator estimates what the shading will cost.
Why exterior shading beats interior blinds
Once sunlight passes through a window and strikes a blind or curtain, most of that energy is already inside the house. The blind absorbs it, warms up and releases heat into the room. An awning intercepts the sun outside, so the absorbed heat stays outdoors and is carried away by moving air. This is why exterior shading devices generally outperform interior treatments at reducing solar heat gain, and why the DOE figures for awnings are high.
Two window ratings help you understand your starting point. Solar heat gain coefficient (SHGC), listed on the National Fenestration Rating Council (NFRC) label, is the fraction of incident solar radiation that ends up as heat inside: lower means less heat gain. Older clear double-pane windows have a relatively high SHGC, while many modern low-E windows are designed for a lower one. The higher your window's SHGC, the more an awning has to save.
How orientation changes savings
The sun's path determines which windows gain the most heat and which awnings help most. The following applies to the Northern Hemisphere, including the continental US.
| Orientation | Summer sun exposure | Awning effectiveness | Design notes |
|---|---|---|---|
| West | Intense, low-angle afternoon sun at the hottest time of day | Highest (DOE: up to 77%) | Low sun gets under short awnings; use deeper projection, side panels or a drop valance |
| South | High midday sun | High (DOE: up to 65%) | A modest projection blocks high summer sun; low winter sun can still enter for passive heating |
| East | Low morning sun, cooler part of the day | Moderate | Like west, low sun angles need deeper coverage; lower cooling impact because mornings are cooler |
| North | Little direct sun except early and late in midsummer | Low | Rarely worth shading for energy |
West glass matters most because its peak sun arrives in late afternoon, when outdoor temperatures are highest and the air conditioner is already working hardest. South windows are easier to shade: the summer sun is high, so a fixed awning with a projection of about 1/2 to 2/3 of the window height blocks most of it. On east and west windows, deeper projection or side panels are needed to stop low-angle sun. See the window awnings guide for sizing, and model shade at your latitude with the shade calculator.
Worked example: estimating cooling savings
The following estimate uses simple, clearly stated assumptions. Your numbers will differ, but the method shows the order of magnitude and where the savings come from.
Worked example: west-facing glass, cooling season
Assumptions
- West-facing glass area: 60 sq ft (about 36 sq ft of glass in a sliding door plus two 3 x 4 ft windows: 36 + 12 + 12 = 60 sq ft).
- Average solar energy striking the west glass on a summer day: about 0.3 kWh per sq ft (roughly 3.2 kWh per square meter, a plausible mid-latitude summer value for a vertical west surface; varies by location and cloud cover).
- Window SHGC: 0.5 (an older double-pane window).
- Cooling season: 120 days.
- Average effective reduction from the awning: 60%. This is below the DOE maximum of 77% because no awning blocks every hour of sun and some diffuse light still reaches the glass.
- Air conditioner efficiency: each 1 kWh of electricity removes about 3.5 kWh of heat (a coefficient of performance of 3.5, typical of a reasonably efficient central system).
- Electricity price: $0.17 per kWh.
- For simplicity, all solar heat gain is assumed to become cooling load. In reality some arrives when the AC is off, so this is an upper-end estimate.
Step 1, solar heat entering without an awning: 60 sq ft x 0.3 kWh x 0.5 = 9 kWh of heat per day. Over the season: 9 x 120 = 1,080 kWh of heat.
Step 2, heat blocked by the awning: 1,080 x 0.60 = 648 kWh of heat (about 2.2 million Btu, at 3,412 Btu per kWh).
Step 3, electricity saved: 648 / 3.5 = about 185 kWh.
Step 4, dollar savings: 185 x $0.17 = about $31 per cooling season for this set of windows.
Peak load check: on a clear late afternoon, direct sun on west glass can approach roughly 200 Btu per hour per sq ft. Heat entering: 60 x 200 x 0.5 = 6,000 Btu per hour. Cutting that by 77% at the peak removes about 4,600 Btu per hour, roughly 0.4 tons of cooling (one ton equals 12,000 Btu per hour). That is a significant share of a small room's cooling need at exactly the time it is hardest to keep cool.
The lesson from the numbers: annual dollar savings from one wall of windows are modest, but the reduction in peak heat gain is large. That is why awnings make west-facing rooms feel dramatically more comfortable even when the utility bill changes only somewhat. Savings scale up with more glass, a hotter and longer cooling season, higher-SHGC windows and higher electricity rates. A house in a hot desert climate with 200 sq ft of unshaded west and south glass could see several times the savings in this example.
What increases or reduces savings
- Climate and cooling hours. Long, hot, sunny summers mean more hours where shading displaces air conditioning.
- Window SHGC. High-SHGC glass gains more heat, so shading helps more. On very low-SHGC windows the absolute savings shrink.
- Glass area. Sliding doors and large picture windows on west and south walls dominate solar gain.
- Fabric. Opaque and darker fabrics generally block more solar radiation than light, open-weave fabrics, though a dark fabric runs hotter itself. Ventilated designs and open sides let that heat escape rather than trapping it against the wall. See awning colors and heat.
- Coverage and timing. A retractable awning only saves energy when it is extended. Sun sensors on motorized awnings can extend it automatically on sunny days while you are away.
- Thermostat behavior. If no one runs the air conditioner during the hours of peak sun, the energy saving is smaller and the benefit is mainly comfort.
Winter: let the sun back in
Shading that helps in summer can cost you free heat in winter, especially on south-facing windows where the low winter sun provides useful passive heating. Retractable awnings solve this by rolling up. For fixed window awnings on south walls, size the projection so it blocks the high summer sun but lets the low winter sun reach the glass. In cold climates, store or retract fabric awnings before snow, which they are not designed to carry; see winterizing awnings.
Awnings compared with other cooling measures
| Measure | Typical cost | Strength | Limitation |
|---|---|---|---|
| Window awning (fabric or aluminum) | $250 to $1,500 per window | Blocks sun outside the glass; preserves view below | Fixed units block some winter sun |
| Patio retractable over a slider | $600 to $9,000 depending on tier and motor | Shades glass and patio together | Must be extended to work; retract in wind |
| Exterior solar screen or drop shade | $300 to $1,500 manual, $1,000 to $3,500 motorized per opening | Very effective on low west sun | Reduces view and daylight when down |
| Interior blinds or cellular shades | Usually lower | Inexpensive; help insulate in winter | Heat is already inside the glass |
For west windows with very low late-day sun, a vertical exterior screen often outperforms a short awning. See drop shades and solar screens. For the full price picture across awning types, see the awning cost guide.
Who benefits most
Strong candidates: homes in hot, sunny climates with large unshaded west or south glass, older high-SHGC windows, and rooms that overheat in the afternoon. Weak candidates: homes with mostly north-facing glass, heavy tree cover, modern low-SHGC windows on the sunny sides, or little use of air conditioning. In those cases, buy an awning for outdoor living or comfort, not energy.
Frequently asked questions
How much energy do awnings save?
The U.S. Department of Energy says awnings can reduce summer solar heat gain by up to 65% on south-facing windows and up to 77% on west-facing windows. The resulting dollar savings depend on climate, glass area, window SHGC and electricity rates, and for a typical home are often modest, ranging from tens to low hundreds of dollars a year.
Which windows benefit most from awnings?
West-facing windows benefit most because they receive intense, low-angle sun in late afternoon, the hottest part of the day. South-facing windows are next and are easy to shade with a modest projection because the summer sun is high. East windows benefit less, and north windows usually do not need shading for energy purposes.
Are exterior awnings better than interior blinds for cooling?
Generally yes. Interior blinds catch sunlight after it has passed through the glass, so much of the heat is already inside. An exterior awning stops the sun before it reaches the window and lets the absorbed heat dissipate outdoors. Interior treatments still help with privacy and winter insulation, so many homes use both.
Does awning color affect energy savings?
Color affects how much light passes through and how hot the fabric gets. Darker, more opaque fabrics typically block more solar radiation, while light colors reflect more but may let more light through. Good ventilation around the awning helps carry away absorbed heat. Fabric openness and weave usually matter as much as color.
Will an awning pay for itself through energy savings?
Rarely on energy alone. A window awning on hot west glass in a sunny climate has the best chance, because its cost per opening is relatively low. Patio awnings usually cost far more than their annual cooling savings, so they are better justified by comfort and usable outdoor space, with energy savings as a bonus.
Sources and further reading
- U.S. Department of Energy, Energy Saver: Energy Efficient Window Attachments
- National Fenestration Rating Council (NFRC): understanding window energy performance labels and SHGC
- ASHRAE Handbook: Fundamentals, chapter on fenestration and solar heat gain
- Efficient Windows Collaborative: window selection and shading guidance
How we write our guides: figures are typical US ranges checked against manufacturer documentation, published standards and installer pricing. Read our editorial standards. Spotted an error or outdated detail? Request a correction.