The average cost of an installed fiberglass window is $625 for the most popular sizes.
The total price range based on size and other factors is $300 – $1,200 or more.
Here’s a summary, with a complete fiberglass window cost comparison for all types.
| Window Type | Standard | Custom (1) | Installed Cost | Ave. Installed Cost (2) |
| Single-hung | $155-$875 | $300-$1,900 | $295-$2,300 | $525 per window |
| Double-hung | $180-$1,050 | $375-$2,150 | $320-$1,500 | $650 per window |
| Casement | $255-$900 | $415-$1,675 | $390-$2,125 | $800 per window |
| Awning | $240-$795 | $350-$$1,600 | $380-$2,035 | $745 per window |
| Sliding/Gliding | $170-$915 | $310-$1,900 | $300-$2,285 | $610 per window |
| Fixed | $135-$610 | $190-$800 | $280-$1,265 | $455 per window |
| Bay/Bow | $735-$2,475 | $995-$3,100 | $880-$3,450 | $1,975 per window |
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(1) Custom windows are rarely needed. See Cost Factors below for an explanation.
(2) Average installed cost is for standard windows. For custom windows installed, add $125 to $300 per window to the cost range in the Custom column.
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We’re talking about full-frame fiberglass. Popular fiberglass window brands include Pella Impervia, Milgard Ultra and Essence and Marvin Ultrex.
See Costs by Brand below
Fiberglass Window Cost Factors
Cost factors fall into window factors, accessory factors and installation factors.
Window Factors
- Quality of the Window Brand: There are no cheap fiberglass windows. Most are mid-grade or premium.
- Window Size: Each window type is available in a range of sizes. For example, single-hung and double-hung windows start at about 18”x18” and can be as large as 48”x72”. Those dimensions equal 2.25 square feet to 24 square feet.
- Window Type: As the table shows, fixed and single-hung windows cost less than double-hung and casement windows of the same approximate size. More moving parts and mechanisms raise cost.
- Standard vs Custom Sizes: A few brands offer custom sizing for oddly sized window openings. Due to the extra work involved in production, making custom windows costs significantly more. However, custom windows are rarely used accept in very old homes.
- Off the Shelf vs Semi-Custom: Here’s another distinction. If you go into Lowes or Home Depot and buy fiberglass windows off the shelf, they will cost less than if you order semi-custom windows. The term “semi-custom” means the windows come in standard sizes, but you have options for frame color, hardware, glass package and other features.
- Type of Glass: When ordering semi-custom windows, you’ll find a range of glass packages (also called glazing). The most basic is double-pane glass with low-E coating and air or argon gas between them. If you upgrade to triple-pane or a glass package designed for your climate, cost might be higher. Specialty glass such as hurricane glass, tempered or obscure glass can also cost more.
- Window Color: Fiberglass windows are produced in several colors. Milgard Essence offers 16 colors. Pella Impervia comes in 5 colors. Darker colors often cost more than light colors. Dual-color frames, meaning different interior and exterior colors, cost more too.
- Wood Interiors: Wood is a lovely interior material, but it fares poorly on the exterior where it is exposed to the elements. Milgard Essence is one series with wood interiors and fiberglass exteriors. Cost is higher than for all-fiberglass frames.
Window Extras Factors
There’s more to a window than the frame and glass, obviously. And those extras come at different prices. Most are available on semi-custom fiberglass windows.
- Frame Enhancements: Several brands offer window trim kits to enhance the look of the window. Milgard, as one example, offers five – as seen here.
- Hardware: Most manufacturers make hardware in several finishes. Some are considered premium finishes (rubbed bronze or satin nickel, for example) and cost more.
- Screens: Standard screens cost less than those like Pella InView that don’t disrupt the view as much.
- Grilles/Grids: There are usually 3-8 options for grille styles including between-glass and other styles. Cost varies slightly based on the style you choose.
- Security Features: Pella is one brand that offers integrated security features such as sensors that work with smart home technology.
Window Installation Cost Factors
- DIY vs Pro: Window installation is not high on the list of DIY projects for most homeowners. It’s a challenge to get the window installed properly – and the risk that if you don’t the window won’t work properly, will be drafty and may develop mechanical issues. However, if you do install your own windows, you’ll save $140-$300 per window.
- Who you Hire: If you choose pro installation, then you can hire a qualified handyman at a lower rate or a window contractor and pay more. A handyman is a good choice if you’re ordering windows from a home improvement store. If you order from a window contractor, then installation is often included in the package cost.
Fiberglass Window Cost by Brands
Here are popular fiberglass window brands and their costs.
Prices are for windows only. Fiberglass window installation cost ranges from $140 to $300 per window based on size, window location and other features.
| Window | Milgard Essence | Pella Impervia | Marvin Ultrex | Milgard Ultra |
| Single-hung | $210-$875 | $195-$825 | $170-$735 | $155-$700 |
| Double-hung | $275-$1,050 | $250-$995 | $215-$880 | $195-$865 |
| Casement | $335-$900 | $325-$880 | $295-$850 | $255-$835 |
| Awning | $300-$885 | $315-$875 | $265-$840 | $240-$800 |
| Sliding/Gliding | $260-$915 | $195-$900 | $190-$850 | $170-$815 |
| Fixed | $200-$610 | $190-$550 | $165-$485 | $135-$500 |
| Bay/Bow | $1,100-$2,475 | $1,075-$2,200 | $950-$2,075 | $735-$1,950 |
Tips for Getting the Best Fiberglass Window Prices
We always recommend getting written estimates from several window contractors that know they are competing for your business.
This approach can save you 25% or more when getting new or replacement windows. To prove the point, here is a comparison sampling of windows prices submitted by other readers.
| Example 1 | Windows | # of Windows | Total Cost | Cost per Window |
| Homeowner 1 | Marvin Integrity | 25 | $17,500 | $700 |
| Homeowner 2 | Marvin Integrity | 2 | $2,200 | $1,100 |
| Example 2 | Windows | # of Windows | Total Cost | Cost per Window |
| Homeowner 1 | Milgard Montecito | 18 various | $16,200 | $900 |
| Homeowner 2 | Milgard Montecito | 18 various | $18,900 | $1,100 |
| Example 3 | Windows | # of Windows | Total Cost | Cost per Window |
| Homeowner 1 | Pella Casement | 11 | $22,000 | $2,000 |
| Homeowner 2 | Pella Casement | 8 | $4,100 | $512 |
While we don’t know all the window sizes, it’s easy to see that some contractors charge higher rates than others.
Weeding through window installers in your area, interviewing a handful of them and hiring a qualified company takes time.
If you’d like to expedite the process, consider filling out the fast, convenient form on this page. You’ll get competitive estimates from licensed, experienced window installers in your area.
The service is free, and there is no obligation. Once you receive the estimates, take your time to review Google Reviews, the Better Business Bureau and similar sites to select the best installer for your windows.
