Which Inverter for a 1.5 Ton AC? (1, 1.5 & 2 Ton Sizing)

Short answer: a 1.5 ton AC needs roughly a 2,500-3,500VA pure sine wave inverter on a 24V battery bank. A 1 ton AC sits around 2,000-2,500VA, and a 2 ton AC pushes you to 4,000VA or more on a 48V bank. These are not ordinary home inverter sizes — an AC is the single heaviest thing most households will ever ask a battery to run, and the inverter number must be chosen for the compressor's startup surge, not just its steady draw.

In 25+ years sizing systems across Delhi NCR, the mistake we see most is people bolting an AC onto the same 850VA or 1,100VA inverter that runs their fans and lights, then wondering why it trips the moment the compressor kicks in — or why the backup lasts fifteen minutes. The opposite mistake is just as costly: buying a 5kVA monster and a wall of batteries for a single bedroom AC that only runs an hour before the power returns.

Start with the table below — it is the part people actually search for. The running watts come from the AC's tonnage and efficiency; the inverter VA adds headroom for the compressor's power factor and startup surge; the battery bank is the minimum that can deliver that load without sagging. Two big caveats before you read it: these figures assume a fixed-speed (non-inverter) AC, which is the harder case, and they are deliberately given as ranges because real draw varies with brand, star rating, ambient temperature and how hot your room is. An inverter (variable-speed) AC needs noticeably less, and we cover that below.

Read the table as a starting point for a conversation, not a final spec. The honest version of 'which inverter for a 1.5 ton AC' is: a 2,500VA unit will start and run most 1.5 ton inverter ACs comfortably, but if you have an older fixed-speed 1.5 ton AC, or you want to run the AC alongside fans, lights and a fridge, step up to 3,000-3,500VA so the surge headroom is genuinely there. When in doubt, size up on the inverter and be realistic on the battery — the inverter is a one-time cost, but the battery bank is where the real money and the real backup live.

An air conditioner is not a steady load like a fan or an LED bulb. Its compressor is a motor, and a fixed-speed compressor draws a large inrush current at the instant it starts — typically three to five times its running current for a fraction of a second, as the motor overcomes inertia and the refrigerant pressure. A 1.5 ton AC drawing about 1,500W in steady running can momentarily demand roughly 4,500-6,000W at startup.

If the inverter cannot supply that spike, its overload protection trips, the AC never starts, and you get the classic 'inverter beeps and cuts off' complaint. Size for surge, not for the running watts on the AC's rating plate.

There is a second, quieter reason ACs need extra VA: power factor. An inverter is rated in VA (volt-amperes), but appliances do useful work in watts, and for a motor-driven load the two are not equal. An AC's power factor sits around 0.7-0.8, meaning a 1,500W AC actually presents about 1,500 / 0.75 = 2,000VA of demand to the inverter even before any surge margin.

A '1,500W' AC genuinely needs a 2,500-3,500VA inverter rather than a 1,600VA one once you account for both the power-factor gap and the startup surge. Use the converter below to translate your AC's wattage into the VA it will actually demand.

Worked example: take a fixed-speed 1.5 ton AC with a running load of 1,500W. Divide by a power factor of 0.75 to get the steady demand in VA: 1,500 / 0.75 = 2,000VA. Now add headroom for the startup surge and for the fact that a comfortable working ceiling is about 70-80% of rated VA — so 2,000VA / 0.7 is about 2,860VA, which lands you in the 3,000VA bracket.

For a modern variable-speed inverter AC with a lower running draw and a soft start, the same calculation lets you drop to 2,500VA.

Whether your AC is an inverter AC or an old fixed-speed one changes the whole calculation — and the terminology trips people up because 'inverter' here means two different things. An inverter AC has a variable-speed compressor that ramps up gently and modulates its speed to hold the room temperature, instead of slamming fully on and fully off. For your battery system this is doubly good news: the startup surge is far smaller, and once the room is cool the compressor throttles down and draws much less than its rated maximum.

The same room that needs 1,500W on a fixed-speed AC might settle near 800W — somewhere in the 600-1,000W band — on a 5-star inverter AC once it has pulled the temperature down.

The inverter is the cheap part — choosing a 2,500VA versus a 3,500VA unit changes the price modestly. The battery bank is where the money goes, because running a 1,500W load is roughly fifteen to twenty times heavier than running fans and lights, and the only way to get usable minutes is sheer stored energy — more batteries, in series, of higher capacity. A 24V system needs two 12V batteries in series; a 48V system needs four.

Doubling your desired backup time means roughly doubling the bank. That is the cost that genuinely scales with your expectations.

Use the appliance load tool below to total up everything you actually want on backup — the AC plus the fan, the lights, the phone chargers, maybe the fridge — because the inverter has to carry all of it at once, and the battery has to feed all of it for the whole cut. Sizing for the AC alone and then plugging in three other things is a very common way to end up disappointed.

Most sellers quietly flatter their backup-time numbers. Usable energy from a battery bank is never its full nameplate figure. Take a 24V bank of two 200Ah tubular batteries: nameplate energy is 24V × 200Ah = 4,800Wh, but three derates apply — discharge only to 50% to protect battery life, the inverter is about 80-85% efficient, and at the heavy current an AC pulls a tubular battery delivers roughly 20% less than its C20 rated capacity (a 1,500W load on a 24V bank draws around 60-65A, a C3-C4 rate, so apply a 0.8 high-rate factor).

Multiply it out — 4,800 × 0.5 × 0.8 × 0.8 — and you get roughly 1,500Wh actually usable. On a fixed-speed AC drawing 1,500W that is about one hour, not the 1.3 you would get ignoring the discharge-rate loss. An inverter AC averaging 800W draws far less current, suffers a lighter high-rate penalty, and stretches the same bank to roughly two hours.

The lesson from that table is not 'buy more batteries forever' — it is 'be clear about what you actually need'. In most of Delhi NCR a backed-up AC's real job is to cover the gap during a short evening or overnight cut, not to run all night off-grid. If your cuts are typically 30-90 minutes, a 24V/200Ah bank with an inverter AC is a sensible, affordable target. If you genuinely need three to four hours of AC, you are buying a 48V bank with four big batteries, and at that point you should also be asking whether solar or a different approach makes more sense.

If your reason for wanting AC backup is daytime heat — a home office, a shop, a clinic that runs through Delhi afternoons — batteries are the wrong tool to lean on, because the sun is doing exactly what you need at exactly the time you need it. A grid-tied or hybrid solar system can run the AC directly off the panels during the day, slashing the bill and removing the load from the battery entirely. The battery then only covers evening and night cuts, which keeps the bank and its cost sensible.

The practical split is: solar and hybrid for daytime cooling, a right-sized inverter and battery for evening and overnight backup. The guide on running an AC on solar or an inverter covers the trade-offs and the solar kW it actually takes.

A hybrid PCU (power conditioning unit) is the bridge between the two worlds: it prioritises solar, tops up the battery, and falls back to the grid, so a single box can both cut your daytime AC bill and keep an evening AC running on backup. It costs more upfront than a plain inverter, but if you are going to spend on a big battery bank anyway, the incremental step to a hybrid setup often pays for itself, especially for a shop or clinic with steady daytime cooling load.

For one bedroom through short, predictable evening cuts, a 2,500-3,000VA pure sine wave inverter on a 24V/200Ah bank paired with a 5-star inverter AC is the sweet spot — it starts cleanly, gives around one to two hours, and does not bankrupt you on batteries. For a 2 ton AC in a 2 BHK living room through long, frequent cuts, accept that you are building a 48V system with four batteries and budget accordingly. If your pain is daytime heat and high bills, look hard at solar or hybrid before you pour money into a battery wall that sits idle every sunny afternoon.

Two rules are non-negotiable for AC backup. First, it must be a pure sine wave inverter — never square or modified-wave, because a compressor on a dirty waveform runs hotter, hums, and can fail early. Second, the inverter and bank must be sized for the surge of your specific AC, not a generic number off a website.

Nice Power sizes AC-capable systems for homes, shops and clinics across Delhi NCR, installs them, and takes your old batteries in exchange. An honest seller will show their working — make them do it.