- “Specific yield” is how many kWh one kW of panels produces in a year at a given place.
- It ranges from about 800 in Scotland to 1,700 in Arizona for well-tilted panels.
- Multiply by your kit size and a mounting factor to estimate yearly output.
- Vertical balcony mounting typically delivers around 70% of the ideal tilted figure.
Two identical balcony kits can produce very different amounts of electricity. The biggest factor you cannot change is where you live. Here is how to estimate it.
In this article
The formula
Yearly kWh ≈ kit size (kW) × specific yield × mounting factor × shade factor
For example: an 800 W kit (0.8 kW) in Denver (yield ~1,600) mounted vertically on a south railing (factor ~0.72) with light shade (~0.85): 0.8 × 1,600 × 0.72 × 0.85 ≈ 780 kWh a year.
Typical specific yields
For south-facing panels (north-facing in Australia) at a good tilt, after normal system losses:
| Region | kWh per kW per year |
|---|---|
| Arizona, Nevada, New Mexico, Southern California | ~1,650-1,750 |
| Colorado, Utah | ~1,550-1,650 |
| Northern/Central California | ~1,500-1,600 |
| Texas, Oklahoma | ~1,450-1,550 |
| Florida, Georgia, the Carolinas | ~1,350-1,450 |
| Mid-Atlantic, Midwest | ~1,250-1,350 |
| New York, New England | ~1,150-1,250 |
| Pacific Northwest | ~1,050-1,150 |
| Southern England | ~950-1,050 |
| Northern England, Wales | ~850-950 |
| Scotland | ~780-860 |
| Germany | ~950-1,050 |
| Spain, Portugal, Southern Italy | ~1,450-1,700 |
| Sydney / Melbourne / Brisbane / Perth | ~1,450 / 1,300 / 1,550 / 1,600 |
| Southern Ontario, Quebec | ~1,150-1,250 |
Rounded typical values based on long-term solar resource data (such as NREL’s PVWatts for the US and the EU’s PVGIS for Europe). For your exact address, run those free tools.
Mounting factors
| Mounting | Factor vs ideal |
|---|---|
| Tilted ~30°, facing the equator | 1.00 |
| Nearly flat | ~0.85-0.90 |
| Tilted, facing east or west | ~0.80-0.85 |
| Vertical, facing the equator | ~0.65-0.75 |
| Vertical, facing east or west | ~0.50-0.60 |
At higher latitudes the vertical penalty is smaller, because the sun is lower. See best angle for balcony panels.
Do it for your address
- Use our calculator for a quick regional estimate.
- For precision, use PVWatts (US) or PVGIS (Europe/UK), entering your panel tilt (90° for vertical) and azimuth.
- Adjust for shade by watching your balcony for a day.
Why yields differ so much
- Latitude: closer to the equator, the sun is higher and days are more even across the year.
- Cloud cover: the desert Southwest has far more clear days than the Pacific Northwest or the UK.
- Altitude and air clarity: high, dry places like Denver get more intense sunlight.
- Temperature: very hot places lose some efficiency; mild sunny climates are ideal.
Three quick examples
| Setup | Calculation | Estimated kWh/year |
|---|---|---|
| 400 W, vertical south, Seattle | 0.4 × 1,100 × 0.72 | ~317 |
| 800 W, tilted south, Phoenix | 0.8 × 1,700 × 1.0 | ~1,360 |
| 800 W, vertical west, London, light shade | 0.8 × 1,000 × 0.55 × 0.85 | ~374 |
Frequently asked questions
What’s the difference between kWh and kWp?
kWp (kilowatt-peak) is a panel’s rated power under test conditions. kWh is energy produced over time. Specific yield connects them: kWh per kWp per year.
How accurate are these figures?
They are long-term averages. Any single year can be about 10% higher or lower depending on weather.
Why does PVWatts give me a different number?
It uses your exact location and lets you set tilt, azimuth and losses. Use it for precision; our table is for quick comparison.
Does altitude of the balcony matter?
Not directly. Higher floors often have less shade from trees and neighboring buildings, which does matter.