If you are holding a 5kW rooftop solar quote and wondering how many AC can run in a 5kW solar system, the short version is this: two 1.5 ton inverter ACs comfortably in the daytime, three only with care, and none during a power cut unless you add a battery. What decides it is the time of day and whether you have backup, not the 5kW number alone.
Quick answer: A 5kW system produces roughly 19–22 units a day in Chennai (about 3.8–4.5 units per kW). A 1.5 ton inverter AC draws about 1–1.5 kW while running, so two run together at midday with room left for the house. At night they run on the grid, and in a power cut a standard grid-tied system shuts down completely.
In this guide
- Think in kW at noon, units over the day
- What an AC really draws
- Daytime: two ACs fit, three is a stretch
- Night: the grid, not the sun
- Power cuts: grid-tied means no solar
- 3kW or 5kW: decide by AC count and hours
- What to tell an installer
- Frequently asked questions
- Get your AC load checked before you sign
- Related guides
Think in kW at noon, units over the day
Two different measurements get mixed up. The 5kW is the most power the panels can deliver at one moment, in strong sun. Units (kWh) are what you collect over a day. Your bill is in units, but whether an AC runs right now depends on kW.
Our own figures for a well-installed, south-facing, shade-free system are 3.8–4.5 units per kW per day. For 5kW that is about 19–22 units a day, or roughly 575–685 units a month, which is 1,150–1,370 per two-month TNPDCL bill. Cloud, shade, dust and roof angle move it, so treat it as a range.
What an AC really draws
A 1.5 ton fixed-speed AC typically draws about 1.4–1.8 kW with the compressor on. A 1.5 ton BEE 5-star inverter AC modulates, and on an average hot day often runs at 60–70% of rated power, around 0.9–1.2 kW.
Over an 8-hour stretch that is roughly 8–12 units per AC, which matches the usual rule of thumb that one 1.5 ton AC running 8 hours uses about 12 units at the high end.
Startup draws a surge, but inverter ACs soft-start, and your solar inverter and the grid together absorb it. Fixed-speed units are harsher on a system and swing between full load and off.
Daytime: two ACs fit, three is a stretch
Between about 10 am and 3 pm a healthy 5kW array delivers around 3.5–4.5 kW. Two inverter ACs at 1–1.5 kW each use 2–3 kW, leaving 1–1.5 kW for the fridge, fans, lights and a TV. That is the clean fit.
Three ACs would ask for 3–4.5 kW before anything else is on. It can work for a few hours with inverter models, but the grid tops up the shortfall, and you will not offset those hours fully. Also, a 5kW system cannot be asked for more than it makes; the house simply pulls the rest from the grid, so nothing breaks. You just save less.
Night: the grid, not the sun
Panels make nothing after sunset. A bedroom AC running 10 pm to 6 am draws from the grid, and under net metering your daytime exports are credited against it. That still lowers your bill, but less than running the AC while the sun is up, because exported units are credited at a lower value than the units you avoid buying.
If your ACs run mostly at night, size from your bill and expect credits to do the work, not direct use.
Power cuts: grid-tied means no solar
This is the costliest misunderstanding we see. A standard grid-tied system switches off when the grid goes down, as anti-islanding protection, so that line workers are not electrocuted. Panels on a sunny afternoon will not run your AC during a cut.
To run an AC through a cut you need a hybrid inverter and a battery. Be realistic about what a battery buys: a 5 kWh battery gives only about 2–3 hours of 1.5 ton AC runtime.
Most homes size backup for fans, lights, router and fridge, and add one bedroom AC only if cuts are long and frequent. That is a comfort purchase with a longer payback, and it adds to the price, so decide it deliberately.
3kW or 5kW: decide by AC count and hours
| Size | Units per day | Daytime AC capacity | Suits |
|---|---|---|---|
| 3kW | 11.5–13.5 | One 1.5 ton inverter AC plus basic loads | 1 AC, bills around 900 units per two months |
| 5kW | 19–22 | Two 1.5 ton inverter ACs plus basic loads | 2 ACs, or heavy daytime use |
Figures depend on roof shade, orientation, panel cleaning and whether the ACs are inverter or fixed-speed.
Yes, a 1.5 ton AC runs on a 3kW system, and well, in the daytime. Two ACs on 3kW will lean on the grid during overlap hours. Our rule: if you run two ACs for several daytime hours, or your bill is high, 5kW pays off.
If one AC runs mainly at night and you are home little in the day, 3kW often gives the better return, since extra panels mostly add exports.
Your roof matters too: 5kW needs more shade-free terrace than the 250–300 sq ft a 3kW takes. See our 3kW vs 5kW comparison for the cost side.
What to tell an installer
- Number of ACs, tonnage, and whether each is inverter or fixed-speed (the rating label shows it).
- Hours each runs, and whether that is day or night.
- Your last few TNPDCL bills in units.
- How long and how often your power cuts last.
- Terrace size and any shade from tanks or neighbouring buildings.
With these, we size against your real load rather than a round number. Our sizing guide walks through the same steps.
Frequently asked questions
Does it matter that the inverter is smaller than the panels?
Slightly. The inverter caps output, so it should be matched to the array. Check the inverter warranty separately; our warranty guide explains panel, inverter and workmanship cover.
Can I add a battery later?
Only easily if the system is designed for it. A hybrid inverter can be planned now and the battery added afterwards; converting a plain grid-tied inverter usually means replacing it.
Will running ACs in the day save more than at night?
Yes. Direct daytime use avoids the full grid tariff, while night use relies on the lower-valued export credits.
Get your AC load checked before you sign
The right size depends on your ACs, hours and power cuts, not the headline kW. Arka Solar Energy offers a free site consultation in Chennai where we check your terrace, bills and AC count, and tell you plainly whether 3kW, 5kW or a battery makes sense. Contact us to book.
Related guides
- 3kW vs 5kW Solar System: Which Is Right for Your Chennai Home?
- 3 kW Solar System in Chennai: Units per Day, Price & Savings
- How Much Can a Chennai Home Save with Solar?