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About this tool
Estimate yearly output, bill savings and payback for a plug-in balcony solar kit from tilt, orientation and latitude.
The Balcony Solar Kit Estimator models what a small plug-in balcony solar kit produces once its panels hang vertically off a railing instead of sitting on a well-aimed roof. The yield penalty is geometry, not guesswork: beam radiation scales with the cosine of the angle between the panel and the sun's noon position, so a vertical panel at 19° latitude collects only cos(71°) of the beam, while diffuse sky light scales with the sky view factor (1 + cos tilt) ÷ 2. The result is annual kWh, self-consumption savings and a simple payback.
Open Balcony Solar Kit Estimator on AltFTool — it loads instantly in your browser.
Under 'The kit' enter Number of panels, 'Panel rating (Wp)', 'Micro-inverter AC limit (W)' and 'Installed kit cost (INR)'.
Under 'Where it hangs' tap a mounting preset — 'Flat against the railing (90°)', 'Angled out on a bracket (45°)', 'Well-angled bracket (30°)' or 'Laid nearly flat on the floor (10°)' — then set 'Which way the balcony faces', 'Latitude, degrees (drop the N or S)', 'Peak sun hours a day', 'Extra shading loss (%)', 'Used in the home immediately (%)' and 'Your tariff (INR per unit)'.
Read 'Estimated output a year' in kWh with the daily figure and monthly saving underneath, then 'Yield vs a well-aimed array' alongside the best tilt for your latitude, Specific yield, 'Saving a year' and 'Simple payback'. 'Copy result' copies the estimate.
Beam and diffuse components handled separately, so vertical mounting is penalised realistically.
The vertical penalty is worse near the equator, and the model reflects that.
Values the units you actually use at your tariff, and exports at the feed-in rate you enter.
A two-panel 880 Wp kit hanging vertically on a south-facing balcony at about 19° latitude, with 5.5 peak sun hours and 10% shading, works out near 500 kWh a year — roughly 40% of what the same panels would make well-aimed on a roof. Angle the panels out to 30-45° on a bracket and that rises steeply.
Because the sun is high at midday. At solar noon the angle between a vertical panel and the sun is roughly 90° minus your latitude plus the sun's declination, so near the equator a vertical panel faces the sun almost edge-on and collects only a fraction of the direct beam. It also sees half the sky instead of nearly all of it, halving the diffuse contribution.
For a fixed year-round array, a tilt roughly equal to your latitude facing the equator — about 19° in Mumbai, 28° in Delhi. On a balcony you rarely get that, but any bracket that moves the panels from 90° towards 30-45° recovers a large part of the loss, which is usually the cheapest upgrade available.
Not without approval. Unlike Germany, where plug-in balcony systems up to 800 W are expressly allowed, Indian grid-connectivity rules generally require an application to your DISCOM and an approved net-metering or behind-the-meter arrangement even for very small systems, and your housing society may have its own rules about railings and façades. Check with your DISCOM before buying.
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