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AC Running Cost Calculator

Works out what an air conditioner costs to run from its tonnage and star or SEER rating, and compares what each efficiency band would cost.

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Used when the efficiency is given as ISEER, EER or SEER rather than stars.
The compressor is not at full power the whole time it is on.
Enter your figures and press Calculate.
In short AC Running Cost Calculator is a free online tool on inputtesthub.com that works out what an air conditioner costs to run from its tonnage and star or SEER rating, and compares what each efficiency band would cost. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the AC Running Cost Calculator

  1. Enter the capacity in tons, BTU per hour or kilowatts of cooling.
  2. Give the efficiency as a star rating, or type the ISEER, EER or SEER from the label.
  3. Set the hours a day and your electricity tariff.
  4. Compare the star-rating table to see what a more efficient unit would save.

About the AC Running Cost Calculator

The AC Running Cost Calculator works out what an air conditioner costs to run from its tonnage and star or SEER rating, and compares what each efficiency band would cost. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Finding what a 1.5 ton AC adds to the bill before you buy it.
  • Comparing a 3-star unit against a 5-star one over a summer.
  • Seeing what raising the thermostat two degrees is worth in money.

Details

One tonExactly 12,000 BTU per hour
ISEER to EERMultiply by 3.412 — ISEER is W/W, EER is BTU per watt-hour
1.5 ton, 5-starDraws roughly 1,500 W at full load
1.5 ton, 1-starDraws roughly 1,900 W for the same cooling
ThermostatAbout 6% of the running energy per °C, in a 3–8% band

The maths behind it

This tool uses power in watts = cooling capacity in BTU/h ÷ the efficiency in BTU per watt-hour, where an ISEER or CoP in W/W is multiplied by 3.412 first. Energy = power × hours × average load, and cost is that times the tariff. Every intermediate value is shown on screen, so the result can be checked by hand.

The power figure is derived from the label, not measured, and that is the tool's purpose. Its weakest input is the average load, which is why it is a field rather than a hidden constant. The comparison between two units is far more trustworthy than the absolute figure, because the load assumption cancels out on both sides.

Where this tool stops

Seasonal ratings such as ISEER and SEER already average across a test season, so applying your own load figure on top double-counts part-load behaviour a little and this will read slightly low. EER is a full-load figure and does not have that problem. Neither models humidity, which in a coastal summer is a large part of the work the unit is actually doing.

Explained in our guides

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Frequently asked questions

How is this different from the Electricity Bill Calculator?
That one starts from watts, which is the right input if you know it. Almost nobody knows their air conditioner's wattage — they know it is a 1.5 ton, 3-star unit, because that is what is on the box and on the label. This tool derives the wattage from the capacity and the rating, and that derivation is the whole point.
What is ISEER and why multiply by 3.412?
ISEER is the Indian seasonal efficiency figure and it is dimensionless — watts of cooling per watt of electricity. EER and SEER are stated in BTU per watt-hour instead. Since one watt is 3.412 BTU per hour, an ISEER of 3.5 is the same efficiency as an EER of 11.9. Comparing the two numbers without converting makes a good unit look terrible.
Is a 5-star inverter worth the extra money?
The table shows what each band costs per month at your tariff and hours, so the answer is arithmetic rather than opinion. Take the monthly difference, multiply by the months you use it, and compare against the price gap. In a hot climate with long hours it usually pays back in two to three summers; in a mild one with two months of use it may never.
Why is there an average load setting?
Because no air conditioner runs at full power for every hour it is switched on. A fixed-speed unit cycles off once the room reaches temperature; an inverter unit throttles down and keeps running at lower power. 70% is a reasonable season average. A room set to 18 °C with the door open will run far closer to 100%, and one set to 26 °C in the evening much lower.
Do I need an account to use the AC Running Cost Calculator?
There is no cost and no cap. The AC Running Cost Calculator is not a demo of a paid product, so nothing is held back or watermarked.
Is my data uploaded anywhere?
No. The AC Running Cost Calculator runs entirely in your browser using JavaScript. Your input never reaches inputtesthub.com or any third party — open your browser's Network tab while you use it and you will see no request go out.
What formula does the AC Running Cost Calculator use?
It uses power in watts = cooling capacity in BTU/h ÷ the efficiency in BTU per watt-hour, where an ISEER or CoP in W/W is multiplied by 3.412 first. Energy = power × hours × average load, and cost is that times the tariff. The full working is printed under the result, so you can follow every step rather than trusting a black box.
Who is the AC Running Cost Calculator for?
Typical uses: finding what a 1.5 ton AC adds to the bill before you buy it. Comparing a 3-star unit against a 5-star one over a summer. Seeing what raising the thermostat two degrees is worth in money. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Is there anything the AC Running Cost Calculator cannot do?
Seasonal ratings such as ISEER and SEER already average across a test season, so applying your own load figure on top double-counts part-load behaviour a little and this will read slightly low. EER is a full-load figure and does not have that problem. Neither models humidity, which in a coastal summer is a large part of the work the unit is actually doing. Knowing where a tool stops being trustworthy matters more than the cases where it works.
What figures does the AC Running Cost Calculator work from?
One ton is Exactly 12,000 BTU per hour. ISEER to EER is Multiply by 3.412 — ISEER is W/W, EER is BTU per watt-hour. 1.5 ton, 5-star is Draws roughly 1,500 W at full load. These are printed on the page itself, so you do not have to take them on trust.
Can I rely on this for exact work?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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