BIPV solar glass adds electrical equipment and integration costs, but generates electricity that conventional glass, metal and stone facades do not. It does not automatically provide better insulation or sound control. In the worked example below, a 1,000 m² facade costs an extra RMB 1.2 million and recovers that premium in year 15. Lower electricity output pushes recovery to year 24.
Installed Cost
Compare two complete designs for the same wall area, wind load, weather protection and appearance. The BIPV price needs to include the glazing, framing, wiring, inverters, electrical protection, installation and commissioning. A glass-only price cannot be compared with an installed curtain wall.
| Budget item | Conventional Low-E curtain wall | BIPV facade |
|---|---|---|
| Assumed installed cost per facade area | RMB 1,000/m² | RMB 2,200/m² |
| Total installed cost | RMB 1,000,000 | RMB 2,200,000 |
| Additional investment | Baseline | RMB 1,200,000 |
| Installed generating capacity | None | 140 kWp |
Here, BIPV costs 2.2 times the conventional design. Its complete facade cost is RMB 15.71/Wp; its additional cost above the conventional wall is RMB 8.57/Wp. Those figures describe different costs. They should not appear under the same “cost per watt” heading in a supplier comparison.
For an existing building, add removal, temporary weather protection and any structural upgrades. A new-build budget does not cover those retrofit costs.
Power and Building Performance
Use the finished product’s rated watts and dimensions, not the efficiency of its individual cells. For example, a 300 Wp module covering 2 m² provides 150 Wp/m². Frames and non-generating areas reduce the figure when it is expressed per square metre of the whole facade. Check module specifications separately from solar cell specifications.
Rated power is measured under standard test conditions, including irradiance of 1,000 W/m² and a cell temperature of 25°C. It is not continuous output. Annual generation also depends on orientation, shading, mounting and system losses.[1]
| Measure | BIPV solar glass | Conventional facade |
|---|---|---|
| Electricity | Check Wp/m² and simulated annual kWh separately | No generation unless a separate PV system is added |
| Daylight and view | Cell spacing, coatings and colour affect visible transmittance and view | Low-E glass can preserve a clear view; metal and stone are opaque |
| Insulation | Compare the complete assembly’s U-value in W/(m²·K) | Use the same assembly boundary and test method |
| Solar heat gain | Check SHGC alongside daylight requirements | Low-E coatings and shading can also limit solar heat gain |
| Sound control | Request an assembly test using a stated rating, such as Rw or STC | Compare the same rating; a bare dB number is insufficient |
| Maintenance | Facade upkeep plus electrical inspection, monitoring and equipment replacement | Cleaning, seals, joints, fixings and damaged panels |
Lower U-values mean less heat transfer. Visible transmittance measures daylight, while SHGC measures incoming solar heat; one cannot substitute for another. NFRC reports these as separate performance measures.[2]
There is no universal north-to-south output ratio. A 2026 IEA PVPS study assessed 357 BIPV options across 44 cities in 12 countries and reported that vertical BIPV needed 1.7–2.5 times the rooftop PV area for equivalent annual energy in the assessed comparisons. That is study evidence, not a forecast for a particular wall.[3]
Payback and Lifetime Cash Flow
The budget example assumes 140 kWp, first-year delivered output of 900 kWh/kWp, annual degradation of 0.5%, and full on-site use at RMB 0.80/kWh. It also allows RMB 10,000 a year in additional maintenance and RMB 50,000 for an inverter replacement in year 12. These are calculation inputs, not product guarantees or site predictions.
First-year generation: 140 × 900 = 126,000 kWh.
First-year electricity savings: 126,000 × RMB 0.80 = RMB 100,800.
First-year savings after additional maintenance: RMB 90,800.
Over 25 years, generation totals about 2.97 million kWh. Electricity savings reach RMB 2.374 million. After the RMB 1.2 million premium, RMB 250,000 maintenance allowance and RMB 50,000 replacement, the undiscounted cash surplus is about RMB 874,000. At a 5% annual discount rate, net present value is approximately −RMB 13,500.
| First-year specific yield | First-year generation | Recovery year | 25-year undiscounted surplus |
|---|---|---|---|
| 600 kWh/kWp | 84,000 kWh | 24 | RMB 83,000 |
| 900 kWh/kWp | 126,000 kWh | 15 | RMB 874,000 |
| 1,200 kWh/kWp | 168,000 kWh | 10 | RMB 1,666,000 |
Recovery means the first year in which cumulative, undiscounted savings cover the additional investment and modelled costs. The calculation excludes taxes, financing, subsidies, tariff changes and differences in heating, cooling or lighting demand.
Exported electricity needs a separate value. If 80% is used on site at RMB 0.80/kWh and 20% is exported at RMB 0.30/kWh, the blended value falls to RMB 0.70/kWh. Applying the retail rate to every generated unit would overstate revenue.
Checks Before Ordering
- Yield model: Request 12 monthly generation estimates, actual wall orientation, a 90° tilt for a vertical wall, shading from nearby buildings and explicit system losses. In PVGIS, select the mounting condition that matches the design; terrain-horizon data alone do not replace a local obstruction study.
- Visual sample: Inspect a full-size sample from both sides. Record visible transmittance, cell pattern and colour, rather than accepting “30% transparent” as a guarantee of a clear view.
- Safety evidence: Obtain the applicable electrical and building-system test reports, including fire performance, wind resistance and weather tightness. A standalone “Class A” label without its standard and tested assembly is insufficient. IEA PVPS identifies the need to address both construction and electrical requirements.[4]
- Replacement plan: Ask how one failed module is isolated and removed, what access equipment is needed, and who restores the weather seal. Separate power-output warranty terms from glass, seals, workmanship and inverter cover.
If the wall has poor output, price a conventional facade with a separate rooftop system using suitable residential or commercial rooftop module configurations. Compare total installed costs and annual savings rather than prescribing a fixed percentage of BIPV coverage.