How Much Solar Do You Need to Run a 1.5 Ton AC?

About 3 kW of panels, for a 1.5 ton AC used around 8 hours a day. That matches the AC’s average daily units with solar generation across the year. The panels don’t run the AC at night, though. After dark, the power comes from the grid or a battery.

The calculation

A 1.5 ton inverter AC typically uses around 1 to 1.4 units an hour on a hot Punjab afternoon, and less once the room has cooled. The table uses 1.2 units an hour as a working figure. Your AC’s BEE star label is a better starting point: it shows the rated yearly consumption in units, based on 1,600 hours of use, so dividing that by 1,600 gives a rough units-per-hour figure for your model.

Our estimates assume 102 units a month from each kW of panels, which is about 3.4 a day averaged over the year.

Summer generates more than the yearly average, which helps, since summer is when the AC works hardest.

In Punjab, the AC is often what crosses the 300-unit line

An AC used 8 hours a day adds roughly 288 units a month. For a home that was comfortably under 300 units, that is enough to cross the line, and once a general-category home crosses it, PSPCL charges for every unit used, starting from the first. That is why the AC so often decides whether solar pays here. Is solar worth it with 300 free units has the numbers.

On-grid: the meter does the balancing

With net metering, the panels don’t have to power the AC directly. Daytime generation supplies the house first and any surplus goes to the grid, and at night you draw from the grid. The meter nets the two out over the billing cycle, so an on-grid system is sized on the units you use, and the AC’s running load doesn’t set the size.

Running an AC on batteries is a bigger job

Off-grid, or during a power cut, the inverter has to carry the AC’s load and the batteries have to hold the energy. Four 12 V, 150 Ah tubular batteries give about 3.2 kWh of everyday backup, which a 1.5 ton AC gets through in two to three hours. Cooling a room through the night on batteries takes a much larger bank and inverter, and it rarely makes financial sense. How many batteries a 3 kW system needs goes through the backup maths.

Size it from your own bill

The AC is one load among many. The calculator works from your whole PSPCL bill and recommends the smallest system that takes it to zero.