RetractWise

Awning Energy Savings Calculator

By Retract Wise Editorial TeamUpdated Editorial standards

The U.S. Department of Energy estimates that awnings can reduce solar heat gain by up to 65% on south-facing windows and 77% on west-facing windows. This calculator turns that into kilowatt-hours, dollars and, more usefully, the peak heat your air conditioner no longer has to fight.

A sliding patio door is about 40 sq ft
Clear double pane about 0.7, low-e 0.25-0.4 (on the NFRC label)
Phoenix about 210, Atlanta 150, Chicago 90

Method and assumptions

  1. Sunlight on the glass: typical cooling-season daily solar energy on vertical glass in sunny US climates: about 3.4 kWh/m² west, 3.3 east, 3.2 southwest, 3.0 southeast and 2.3 south (south glass receives less in summer because the sun is high). Multiplied by days and sky factor.
  2. Heat admitted: multiplied by the window's solar heat gain coefficient (SHGC).
  3. Heat blocked: DOE figures of 77% west and 65% south; 72% for east and southwest and 68% for southeast are our interpolations.
  4. Electricity: heat removed divided by an effective COP of SEER ÷ 3.412 × 0.85 (real-world performance is below the rated figure).
Worked example: 60 sq ft of west-facing low-e glass (SHGC 0.4), 150-day season, mixed skies: 3.4 × 150 × 0.8 × 5.57 m² = 2,274 kWh of sunlight; × 0.4 = 910 kWh of heat; × 0.77 = 700 kWh blocked; ÷ COP 3.49 = about 200 kWh of electricity, or roughly $34 a year at $0.17. Peak heat blocked: about 3,700 Btu/h, nearly a third of a ton of cooling.
Retract Wise analysis: with modern low-e windows, annual dollar savings from an awning are real but modest, usually tens to low hundreds of dollars. The bigger effect is peak load: shading a big west window can cut the late-afternoon heat spike that makes one room unbearable, and that is what most owners notice. With older clear glass (SHGC around 0.7), savings nearly double.

For context on how awnings compare with exterior screens and interior blinds, read energy savings from awnings.

Frequently asked questions

Do awnings really lower electric bills?

Yes, when they shade sunlit east, west or south glass during the cooling season. The amount depends on glass area, window type, climate and AC efficiency; use the calculator above with your numbers.

Why does the DOE figure differ by orientation?

West and east windows get low-angle sun that pours straight through glass; an awning intercepts a large share of it. South windows get high summer sun that the wall overhang and window recess already partly block.

Does awning color affect energy savings?

A little. Light colors reflect more heat away; dark colors absorb more but re-radiate much of it outdoors. See fabric colors and heat.

Do I need to keep the awning out all day?

Only when the sun is on the glass. A sun sensor can extend the awning automatically when the window is in direct sun.