Is a Solar Window Right for Your Project?

Solar windows are a significant investment, and not every building or homeowner is an ideal candidate. Before diving into product specifications, ask yourself a few foundational questions:

  • Do you have large glazed surfaces (facades, skylights, atriums) that receive direct sunlight?
  • Is rooftop space limited or architecturally unsuitable for traditional panels?
  • Is aesthetics a priority — for example, a heritage building or modern commercial facade?
  • Are you planning a new build or a retrofit?

If you answered yes to most of these, solar windows deserve serious consideration. If you have ample, unshaded roof space, traditional panels may still deliver better value per watt today.

Key Specifications to Evaluate

1. Power Conversion Efficiency

Efficiency tells you how much of the sunlight hitting the window is converted to usable electricity. Commercial solar windows currently range from about 3% to 15% depending on technology. While this is lower than rooftop panels (18–22%), the key metric for buildings is watts per square meter of facade, since windows replace glass that would otherwise produce zero energy.

2. Visible Light Transmittance (VLT)

VLT determines how much natural light enters the building. Higher VLT means a brighter interior but generally lower efficiency. Match VLT to the window's function:

  • Offices and living spaces: aim for 40–70% VLT
  • Skylights: 30–60% may be acceptable
  • Privacy or decorative panels: lower VLT may be acceptable

3. U-Value and Solar Heat Gain Coefficient (SHGC)

Solar windows should still perform as thermally efficient glazing. Look for a U-value below 1.2 W/m²K (double-glazed performance) and an SHGC that suits your climate — lower SHGC for hot climates to reduce cooling loads, higher SHGC for cold climates to capture passive solar heat.

4. Durability and Certifications

Look for products certified to relevant standards such as:

  • IEC 61215 / IEC 61646 — PV module durability standards
  • EN 1279 — Insulated glass unit performance (Europe)
  • ANSI/NFRC ratings — Fenestration performance (North America)
  • Local fire and impact resistance ratings for your jurisdiction

5. Warranty

A quality solar window should come with:

  • A product warranty of at least 10 years covering manufacturing defects
  • A performance warranty guaranteeing output above a certain threshold (e.g., 80% of rated output) for 20–25 years

New Build vs. Retrofit

Solar windows are easiest — and most cost-effective — to integrate during new construction, when framing, wiring, and inverter placement can be planned from the outset. Retrofitting existing windows is possible but involves additional labour for removal, wiring runs, and potentially upgrading frames to handle the added weight of laminated PV glass.

Choosing a Supplier

The solar window market includes established glazing manufacturers who have added PV capabilities, as well as pure-play solar glazing startups. When evaluating suppliers, consider:

  • Track record — How many installed projects do they have? Can they provide references?
  • Local support — Is installation support and after-sales service available in your region?
  • Integration capability — Can they work with your existing building management system (BMS)?
  • Custom sizing — Can they manufacture panels to non-standard dimensions for your project?

Financial Considerations

Solar windows typically cost more per watt than conventional panels due to the complexity of the glass manufacturing process. However, the cost comparison should account for the fact that you are replacing glazing you would have purchased anyway. The relevant comparison is: cost of solar glazing minus cost of standard high-performance glazing = true incremental cost of solar.

Always investigate available incentives — many regions offer tax credits, grants, or accelerated depreciation for building-integrated solar, and solar windows often qualify.

Final Checklist

  1. Assess your glazing area and sun exposure.
  2. Define your VLT and thermal performance requirements.
  3. Request product data sheets and third-party test reports.
  4. Compare total installed cost (not just product cost).
  5. Verify warranties and supplier support.
  6. Check local incentives and grid connection requirements.