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Yes, an inverter can run an AC. Three things have to line up: the inverter has to survive the compressor’s startup jolt, the battery has to be big enough for the runtime you want, and the type of compressor matters more than most people expect.
Here is the part that catches everyone out.
A 1.5 ton AC draws roughly 1.2 to 1.8 kW while it runs. That number is easy to find. But for a split second when the compressor kicks in, it pulls five to six times that much. Published compressor data sheets show a unit rated at 5.4 amps running that spikes to 32 amps at the moment it starts.
A small 12V home inverter cannot deliver that jolt. So it trips, or the AC just refuses to start. The inverter was never too weak to run the AC. It was too weak to start it.
Truepower, an inverter and power-backup brand of Indo Solar Systems LLP based in Delhi, India, builds this sizing logic into its lithium and hybrid ranges. If you are new to lithium backup generally, our complete buyer’s guide to lithium inverters for the home covers the fundamentals this piece assumes.
TL;DR: A 1.5 ton inverter-type AC draws roughly 0.8 to 1.8 kW depending on how hard the compressor is working. Running it on backup needs a pure sine wave inverter rated well above that, plus a 48V lithium battery sized for the hours you want. The startup spike, not the running load, is what decides whether the inverter copes. Truepower builds its upper KIVO hybrid range on 48V for exactly this job. Every runtime figure below is an estimate, and it moves with room temperature, set point and star rating.
Can an Inverter Run a 1.5 Ton AC?
Yes, an inverter runs a 1.5 ton AC when the inverter, the battery and the compressor type all match the load.
A 1.5 ton AC draws roughly 1.2 to 1.8 kW at full load. Once the room cools down to your set point, an inverter-type unit eases off to around 0.8 to 1.2 kW, because the compressor slows instead of shutting off.
We size for the startup spike first and the runtime second. An inverter matched only to the running watts will still cut out the moment the compressor starts. The same principle applies to every appliance you put on backup, which is why our guide to choosing the right inverter capacity for your home separates what runs at once from how long it runs.
A quick warning about the star label
The star label is the most commonly misread number in this whole exercise.
The Bureau of Energy Efficiency assumes about 1,600 cooling hours a year on every label, as explained by the Citizen consumer and civic Action Group. A Centre for Science and Environment analysis, published in Down To Earth, puts a 5 star 1.5 ton inverter AC near 740 kWh a year, against roughly 1,008 kWh for a 3 star unit.
That tells you what the AC costs to run. It does not tell you what the AC draws.
The two are different things. kWh is energy used over time, like the total distance a car travels. kW is the rate of draw right now, like its speed at this moment. Divide the annual kWh by 1,600 hours and you get an average speed for the whole season, including every mild evening and every hour the compressor was barely working. It lands far below the real running draw, and it tells you nothing at all about the startup spike.
Use the annual kWh to estimate your bill. Size your inverter off the running load and the startup spike.
Why the Starting Surge, Not the Running Watts, Decides It
The number that trips an undersized inverter is the compressor’s startup surge, not its running draw.
Think of a compressor motor as a heavy flywheel. Getting it spinning from a dead stop takes far more effort than keeping it spinning. In electrical terms, a stationary motor briefly pulls five to six times its normal current before it gets going.
A published Tecumseh rotary compressor data sheet shows this clearly. The unit is rated at 5.4 amps running. At the instant it starts, it pulls 32 amps. That is nearly six times higher, for a fraction of a second.
This ratio comes from how the motor itself is built, so it holds true as tonnage goes up. A bigger AC has a bigger spike.
One more thing worth clearing up: tonnage is a cooling measurement, not an electrical one. A ton means 12,000 BTU of cooling per hour. The electricity needed to deliver it is a fraction of that number, which is why a 1.5 ton AC does not draw anything close to 1.5 kW per ton.
Truepower reads the surge ratio straight off the compressor nameplate. That is why our upper KIVO hybrid range runs on a 48V bus with kVA surge headroom, sized for the spike the inverter has to survive rather than the load it has to carry.
Why an Inverter-Type Compressor Changes the Answer
An inverter-type AC is far easier to run on backup, because it avoids the startup spike almost entirely.
A fixed-speed AC connects its compressor straight to the mains. Every time it cycles on, you get the full jolt. Then it switches off, and a few minutes later you get it again.
An inverter-type AC works differently. It uses a variable-frequency drive, which is a controller that starts the motor slowly and winds it up gradually, like easing a car forward instead of dropping the clutch. There is no violent start, so there is no big spike.
The numbers show the difference plainly. A published 18,000 BTU inverter split submittal lists 8.1 amps running against 20 amps at startup, about 2.5 times. A fixed-speed compressor of the same class hits five to six times.
Once running, an inverter-type unit also throttles its speed to match the cooling the room actually needs, so the running draw drops as the room gets cold. The Bureau of Energy Efficiency runs a separate star-rating schedule for these variable-capacity units, confirming they modulate rather than switch on and off.
We plan 1.5 ton backup around inverter-type ACs for this reason. The gentle start keeps everything inside what our inverters handle.
What Size Inverter Do You Need to Run an Air Conditioner?
You need a pure sine wave inverter rated well above the AC’s running watts, with surge headroom for the startup spike, on a 24V or 48V battery.
Four checks. Skip any one and a properly powered AC still fails to start.
1. Continuous rating above the running load
For a 1.5 ton AC pulling up to about 1.8 kW, add the indoor and outdoor fans on top of the compressor, and your inverter’s continuous rating should sit comfortably above 2 kW. Go higher if lights and fans share the same inverter.
Do not size to the exact running watts. The AC works hardest in the first stretch after you switch it on, while it drags a hot room down to temperature. Our guide to matching inverter capacity to household load walks through the same arithmetic for the rest of the house.
2. Surge rating above the startup spike
A fixed-speed compressor needs surge headroom of several times its running draw, to cover that five-to-six-times jolt. An inverter-type AC starts gently, so it needs far less, around 2.5 times.
3. Pure sine wave output
An AC compressor needs a clean waveform. A square-wave or modified-sine inverter runs the motor hot, wastes power, and may stop it starting at all. Every AC-capable Truepower inverter, across the Lithvon lithium and KIVO hybrid ranges, outputs pure sine wave.
4. Battery voltage of 24V or 48V
This is the check people skip, and it decides whether the whole system is practical.
The power your AC needs is fixed. But the current your wiring has to carry depends on the battery voltage, because current equals power divided by voltage. Lower voltage means higher current for the same job.
For a steady 1.5 kW load, allowing for inverter losses:
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12V bank: about 139 amps
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24V bank: about 69 amps
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48V bank: about 35 amps
Same AC. Four times the current at 12V compared to 48V.
Current is what generates heat in cables, and heat losses climb steeply, not gradually. Halve the current and heating losses drop to a quarter. Go from 12V to 48V and they drop to roughly a sixteenth.
In practice this decides how thick your cables need to be, how big your fuses are, how much voltage sags at the inverter when the compressor kicks in, and how much of your stored power is wasted heating up wire instead of cooling your room. And remember, during startup the current is several times higher again — which is exactly when a marginal cable or a loose connection becomes a hot spot.
A 12V bank at AC-class loads needs impractically heavy cable and still wastes a meaningful share of the battery. This is why Truepower builds the upper KIVO hybrids on 48V for AC loads, and keeps the 24V Lithvon lithium builds for lighter 1 ton duty.
How Long Will a Battery Run an AC During a Power Cut?
A battery runs an AC for as long as its usable energy divided by the AC’s running watts, adjusted for inverter losses.
The word doing the work there is usable. You never get to use a battery’s full nameplate capacity.
Battery University, the neutral technical reference from test-equipment maker Cadex Electronics, notes that lithium cycle life is specified at 80% depth of discharge. Power-Sonic, a battery maker, rates a lead-acid deep-cycle cell near 200 cycles against a lithium cell’s 2,000 plus. In practice, lead-acid should not go below about 50% charge, while lithium iron phosphate (LiFePO4) runs comfortably down to 80 to 100%. We put numbers to that gap over a decade of ownership in our LiFePO4 versus lead-acid tubular comparison for Indian conditions.
For an AC, though, that gap is the second problem. The first is that a 12V lead-acid setup cannot deliver the compressor’s starting jolt at all, so it never gets as far as a runtime calculation. That is why every figure below is lithium, and why Truepower puts the upper KIVO hybrids on a 48V LiFePO4 bus and builds the Lithvon range on LiFePO4 throughout.
Worked example: a 48V 100Ah LiFePO4 battery holds 4,800 Wh on paper and about 4,320 Wh you can actually use. Running a 1.5 ton inverter AC at around 1.2 kW, that is roughly 3.2 hours.
| Battery bank (chemistry) | Nominal Wh | Usable Wh | AC running load | Estimated runtime |
|---|---|---|---|---|
| 48V 100Ah LiFePO4 | 4,800 | ~4,320 (90% DoD) | 1.5 ton inverter AC, ~1.2 kW | ~3.2 hours |
| 48V 200Ah LiFePO4 | 9,600 | ~8,640 (90% DoD) | 1.5 ton inverter AC, ~1.2 kW | ~6.5 hours |
| 48V 100Ah or 24V 200Ah LiFePO4 | 4,800 | ~4,320 (90% DoD) | 1 ton inverter AC, ~0.9 kW | ~4.3 hours |
| 48V 200Ah LiFePO4 | 9,600 | ~8,640 (90% DoD) | 1 ton inverter AC, ~0.9 kW | ~8.6 hours |
| 48V 150Ah tubular battery (4 batteries in parallel) | 7,200 | ~3600 (50% DoD) | 1 ton inverter AC, ~0.9 kW | ~4 hours |
In the above table, as you can see we have also included a 24V 200Ah battery for a 1 ton AC because the current draw on startup stays below 200 Amps (1C) and thus the standard BMS works fine. But this is not the case when the AC is 1.5 ton, the startup surge for which draws beyond 200 amps (beyond 1C for a 200Ah battery pack) which requires for a bigger BSM for the battery pack
These assume about 90% inverter efficiency and are estimates, not promises.
The relationship is simple: double the battery, roughly double the runtime. We never quote a fixed backup time, because the real figure moves with room temperature, your set point, the star rating and how hard the compressor is working that day.
Which Truepower Inverter Fits a 1 Ton or 1.5 Ton AC?
For either size, we point to the upper KIVO hybrid range, available on a 24V or 48V battery bus. For a 1.5 ton AC we specify the 48V builds.
The KIVO Max is rated at 6.5 kW continuous with a 12 kVA surge. The KIVO Ultra is 12 kW with a 24 kVA surge. Both run on 48V.
Put a 1.5 ton inverter AC against those numbers and it is comfortable. At 1.5 to 1.8 kW running, it sits well inside the 6.5 kW rating, and even a fixed-speed unit’s startup spike fits inside the surge headroom with room to spare. If you are already considering solar, the same hybrid platform lets you run the house on solar and bank the surplus, which changes the running-cost maths on an AC considerably.
For a 1 ton inverter AC on a modest battery, our Lithvon lithium range handles it with pure sine wave output, in 24V builds up to 3,000 VA. For what these systems cost across capacities, see our lithium inverter price breakdown from 1000VA to 5000VA.
One Truepower product does not belong anywhere near an AC: our SIGNATURE square wave inverter. It is built for basic loads like lights and fans, and its square-wave output would run a compressor motor hot. For any air conditioner, pick a pure sine wave unit from the Lithvon or KIVO range.
Not sure which fits your load? Talk to our team or browse the full range.
Frequently asked questions
- Can an inverter run a 1.5 ton AC?
- Yes, provided the inverter can handle the compressor’s startup surge, the battery is sized for the runtime you want, and the AC is inverter-type (or the inverter has enough surge headroom for a fixed-speed unit). A 1.5 ton AC draws roughly 1.2 to 1.8 kW running, and a fixed-speed compressor briefly pulls five to six times that at startup. A small 12V home inverter cannot deliver that spike. Truepower sizes its upper KIVO hybrids on a 48V bus for this load, pairing pure sine wave output with lithium storage.
- What size inverter do I need to run an air conditioner?
- You need a pure sine wave inverter with a continuous rating comfortably above the AC’s running watts, surge capacity that clears the startup spike, and a 24V or 48V battery bank. For a 1.5 ton AC drawing up to about 1.8 kW, that means a continuous rating above 2 kW plus several times that in surge for a fixed-speed compressor. A 12V bank draws impractical current at this load, so 48V is the sensible choice. The Truepower KIVO Max is rated at 6.5 kW with a 12 kVA surge on 48V, well above a 1.5 ton AC.
- How long will a battery run an AC during a power cut?
- Divide the battery’s usable watt-hours by the AC’s running watts, then allow for inverter losses. A 48V 100Ah LiFePO4 battery holds about 4,320 usable watt-hours, which runs a 1.5 ton inverter AC at around 1.2 kW for roughly 3.2 hours, or a 1 ton unit at around 0.9 kW for roughly 4.3 hours. A 12V lead-acid battery does not enter this calculation, because it cannot supply the compressor’s starting surge in the first place. Truepower treats all of these as estimates, never fixed backup times.
- Can an inverter run a 1 ton AC?
- Yes, and more easily than a 1.5 ton unit, because it simply draws less. A 1 ton split AC pulls roughly 0.9 to 1.2 kW at full load, and an inverter-type 1 ton eases off further once the room cools. A pure sine wave inverter above about 1.5 kW continuous, on a 24V or 48V lithium bank, handles it with headroom for the compressor surge. The Truepower Lithvon lithium range covers a 1 ton inverter AC with pure sine wave output and 24V builds up to 3,000 VA.
- Do I need a pure sine wave inverter for an AC?
- Yes. A compressor motor runs hot and inefficiently on a square-wave or modified-sine output, and may fail to start on it altogether. This is why we do not recommend the Truepower SIGNATURE square wave inverter for any air conditioner — it is built for lights and fans, not compressors. Every AC-capable Truepower inverter, across the Lithvon lithium and KIVO hybrid ranges, outputs pure sine wave. For an AC on backup, the waveform matters as much as the capacity.
- Why is an inverter AC easier to run on backup than a normal AC?
- Because it starts its compressor gently. An inverter-type AC uses a variable-frequency drive that winds the motor up gradually, avoiding the hard jolt a fixed-speed AC produces every time it cycles on. That fixed-speed jolt is five to six times the running current, and it is what trips an undersized inverter. An inverter-type unit also throttles down to a lower running draw once the room is cold. Truepower plans 1.5 ton backup around inverter-type ACs so the gentle start stays within our inverters’ surge headroom.
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