What size inverter for a 1.5 ton AC?
Running a 1.5 ton AC on an inverter, with two lights. Possible, but it needs a big inverter and a big battery bank.
- Typical appliance watts, change them in the calculator
- Indian inverter sizes
- Tubular or lithium
The load
Typical ratings. Check the plate on your own appliances; a BLDC fan uses about 30 W instead of 75 W.
| Appliance | How many | Watts each | Total |
|---|---|---|---|
| Air conditioner (1.5 ton) motor | 1 | 1500 W | 1500 W |
| LED bulb | 2 | 9 W | 18 W |
| Running load | 1518 W |
Battery for the backup you want
Tubular: 12 V batteries, the usual choice. Longer backup moves you to a 24 V inverter with two batteries. Lithium: LiFePO4 modules.
| Backup | Tubular battery | Inverter for that | Lithium |
|---|---|---|---|
| 2 hours | 3 × 165 Ah tubular | 3200 VA, 36 V | 6 × 12.8 V 100 Ah lithium |
| 4 hours | 3 × 260 Ah tubular | 3200 VA, 36 V | 9 × 12.8 V 100 Ah lithium |
| 6 hours | 4 × 260 Ah tubular | 4200 VA, 48 V | 12 × 12.8 V 100 Ah lithium |
| 8 hours | Too long for a home bank | — | 4 × 51.2 V 100 Ah lithium |
What it adds to your bill
| Power cuts a day | Recharging | Standby | Adds to your bill |
|---|---|---|---|
| 1 h | 71.2 units | 18.4 units | 89.5 units a month |
| 2 h | 142.3 units | 18.4 units | 160.7 units a month |
| 4 h | 284.6 units | 18.4 units | 303 units a month |
Inverters in our list that fit
From the makers’ stated ratings, smallest first. Brands are not ranked.
| Model | Rating | Battery | Wave |
|---|---|---|---|
| V-Guard Synergy Smart 3750 | 3200 VA / 2550 W | 36 V | Pure sine wave |
Questions
How is the inverter size worked out?
Running watts × 1.25 for a safety margin ÷ 0.8, the power factor Indian brands rate their inverters at. Then we pick the next standard size. Motors such as a fridge or pump also need starting surge, which we check against the inverter’s rating.
Why do the hours change the battery but not the inverter?
The inverter sets how much can run at once; the battery sets for how long. Longer backup needs more Ah, and past what one 12 V battery can give, a 24 V inverter with two batteries.
Will this raise my electricity bill?
Yes, a little. The battery is recharged from the grid after every cut, with some loss, and the inverter draws standby power all day. Each page shows the units a month; the calculator prices them at your state’s slabs.