How many solar panels do you need to run an air conditioner?

By the SmartSolarSizer team · Published 20 October 2026

Tons and BTU are cooling, not watts

The size printed on an air conditioner is the wrong number to size solar with. A 1 ton unit removes 12,000 BTU of heat an hour, about 3.5 kW of cooling, but it doesn't draw anything like 3.5 kW from the wall, because a compressor moves several units of heat for every unit of electricity it uses. Read "1.5 ton" as 5.3 kW of load and you'd buy about 3 times the panels you need.

To get electrical watts, divide the cooling by the efficiency rating:

An ENERGY STAR window unit rated CEER 15 works out at 12,000 ÷ 15 = 800 W (ENERGY STAR). Central systems sold in the US must reach at least 13.4–14.3 SEER2, depending on the region (Carrier), and ENERGY STAR certified 2 and 3 ton air-source heat pumps, which cool the same way as central AC, have a median EER2 of 12.5 and 12.0 (ENERGY STAR data). Those medians give the central figures here.

The split AC figures are our own planning values for full load in very hot climates such as Pakistan, India and the Gulf, and the same ones our calculator uses. Check your unit's rated input watts on its spec sheet. An inverter AC spends much of its time below full load, so its real use is often lower.

Window and portable ACs from 5,000 to 15,000 BTU

Small units are where the BTU method is most useful, because the box often shows nothing but the cooling size. ENERGY STAR's sizing chart matches a 5,000 BTU unit to a room of 100–150 ft² (about 9–14 m²), 8,000 BTU to 300–350 ft² and 12,000 BTU to 450–550 ft² (ENERGY STAR). Two certified CEER 15 units anchor the table: the 8,000 BTU one is labelled 400 kWh a year (ENERGY STAR) and the 12,000 BTU one 600 kWh. For the sizes in between we've applied the same CEER 15, so read those rows as estimates.

A portable AC follows the same sum, using the CEER on its own label. Efficiency moves the answer a lot: at CEER 12, the 10,000 BTU unit would draw about 833 W instead of 667 W. If the spec sheet lists input watts, use that figure and skip the division.

How many hours a day will your AC run?

Hours matter as much as watts, and they're easy to underestimate. Every figure on this page assumes 8 hours a day at full power. The full-power part is the cautious bit: the certified 12,000 BTU window unit's 600 kWh a year is about 750 hours at 800 W, or 94 days of 8 hours, and an inverter AC throttles back once the room is cool. If you run yours 12 hours, the energy goes up by half. Put your real hours into the estimator rather than scaling the tables, because panel counts round up.

Solar panels for a 1 ton, 1.5 ton, 2 ton or 3 ton AC

Take a 1.5 ton inverter split AC in Lahore. At 1,600 W for 8 hours it uses 12.8 kWh a day. One 430 W panel there makes 1.89 kWh on an average day, so you need 7 panels. In July, monsoon cloud cuts output to 3.57 kWh per kW and the count rises to 9. July is also when the AC works hardest, so that's the number to plan on.

Here's the 1.5 ton inverter AC (12.8 kWh a day) in all 14 locations. The last column is the peak cooling month (July, or January south of the equator):

Look at which way the last column moves. Across most of the US and Europe, July beats the yearly average, so the average-day count already has slack in it. Phoenix, Dubai, Johannesburg and South Asia go the other way, Lahore, Karachi and Delhi most of all.

How many solar plates for a 1 ton, 1.5 ton or 2 ton AC?

In Pakistan and India, panels ("solar plates") of 545–585 W are the usual size, so here are the same loads with 550 W plates. The 2 ton row is our estimate: we don't have a sourced figure for a 2 ton split, so we've scaled the 1.5 ton planning figure by size, to about 2,100 W.

The monsoon adds 1 or 2 plates in July. The bigger difference is the compressor: in a Lahore July the non-inverter 1.5 ton AC needs 2 more plates than the inverter model for the same cooling, and it brings a far bigger start-up surge. If you haven't bought the AC yet, spend on an inverter model before you spend on extra plates. Our 1.5 ton AC guide walks through that case step by step.

How many ACs can a 3 kW solar system run?

One 1.5 ton inverter AC for most of a sunny day, with little to spare. A 3 kW array (seven 430 W panels, or roughly six 550 W plates) makes about 13.2 kWh on an average day in Lahore and 10.7 kWh in July. At 1,600 W that's 8.3 hours of full-power cooling on an average day and 6.7 hours in July, before the fridge, fans and lights take their share.

Two 1 ton inverter ACs together draw 2,200 W. The same array covers both for about 6.0 hours on an average Lahore day and 4.9 in July, and only around midday: a 3 kW array rarely delivers its full rating, so 2,200 W leaves little margin.

Two 1.5 ton ACs

Running two 1.5 ton inverter ACs for 8 hours takes 25.6 kWh a day: 11 plates of 550 W in Lahore on an average day and 14 in July. The inverter needs at least 4,000 W continuous (3,200 W × 1.25). If both compressors start together, the surge reaches about 4,000 W, so set their timers a few minutes apart. Overnight the pair would need 31.6 kWh of battery, which is why a more realistic plan is both units by day and one, set a few degrees warmer, after dark.

Can you run central AC on solar power?

Yes, and on a grid-tied home it's simpler than it sounds. The panels don't have to carry the compressor moment by moment; you size the array to offset its kWh and the grid covers the gaps. A 2 ton variable-speed system at about 1,900 W uses 15.2 kWh in 8 hours, which is 8 panels in Phoenix and 10 in Houston. A 3 ton single-stage system at 3,000 W uses 24.0 kWh: 12 and 15.

Off-grid is a different job. A single-stage compressor starts at full power, and Home Depot's generator guide puts motor start-up at about three times running watts (Home Depot), so we give the 3 ton unit a 9,000 W surge. A variable-speed system ramps up instead (our planning figure is 2,100 W for the 2 ton). If you ever plan to run central air from a battery, that's the type to buy.

What size inverter runs an AC? Watch the start-up surge

Panels decide how long the AC runs. The inverter decides whether it starts at all. A fixed-speed (non-inverter) compressor slams on at full power and pulls several times its running current for a moment, and that spike is what trips small inverters. The rule on these pages is a continuous rating of at least 1.25 × running watts, rounded up to a standard size, plus a surge rating that covers the start:

• 8,000 BTU window unit: 1,000 W continuous, with surge to 1,600 W.
• 1.5 ton inverter split AC: 2,000 W continuous. The compressor ramps up, so the start (our planning figure: 2,000 W) barely exceeds the running power.
• 1.5 ton non-inverter: 3,000 W continuous and a surge rating of at least 5,000 W (our planning figure; Home Depot's three-times rule would put it nearer 6,600 W), or a soft starter. One maker says its soft starter cuts start-up current by up to 75% (Micro-Air).
• 3 ton single-stage central AC: 4,000 W continuous and 9,000 W surge.

The main calculator is stricter. It sets the continuous rating at 1.25 × the surge, so it may suggest a bigger inverter than this list. If you don't know your unit's start-up draw, go with the bigger number.

Can solar panels run an AC at night?

Only through a battery or the grid. The panels stop at sunset; the heat doesn't.

Eight hours of a 1.5 ton AC at full power needs 12.8 ÷ 0.81 = 15.8 kWh of lithium battery, a big bank for one appliance. An 8,000 BTU window unit needs about 5.2 kWh for the same hours. Both are full-power figures, and an inverter AC on a cooler night draws less. Still, the cheapest kWh is the one you never store. Run the AC hardest between late morning and mid-afternoon, cool the house down before sunset, then raise the thermostat a few degrees and let ceiling fans do the rest. Cutting the night run from 8 hours to 4 halves the battery.

Running an air conditioner without a battery

On a grid-tied system that's normal. The panels supply the AC while the sun shines and the grid fills any gap, so a passing cloud changes your bill, not your comfort. With net metering, daytime surplus also offsets what you use at night.

Off-grid, or on a hybrid system during load-shedding, it's harder. Some hybrid inverters can run loads straight from the panels, but then what counts is power at that moment, not energy over the day. A 1.5 ton inverter AC at full load wants 1,600 W continuously, panels reach their rated output only in strong sun, and system losses take another slice. A cloud can push output below what the compressor needs, and the inverter drops it. If you want to try, make the array well over 1,600 W, run the AC from late morning to mid-afternoon, and add even a small battery to ride through the clouds.

Common questions

Sources

Solar output for every location comes from the European Commission's PVGIS 5.3 (1 kW system, panels at the best fixed angle facing the equator, 14% system losses), retrieved 20 October 2026. Panel counts assume 430 W panels, the most common size in 2025 home solar quotes (EnergySage).

• ENERGY STAR: room air conditioners (sizing chart)
• ENERGY STAR certified room AC, 8,000 BTU, CEER 15 (400 kWh/yr)
• ENERGY STAR certified room AC, 12,000 BTU, CEER 15 (600 kWh/yr)
• ENERGY STAR certified air-source heat pumps and central AC dataset
• Carrier: US minimum efficiency standards (SEER2)
• Home Depot: choosing the right size generator (motor start-up watts)
• Micro-Air EasyStart Flex soft starter

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