April office chat is always the same.
Someone says 1.5 ton, 8 hours, how much extra on the bill.
Someone else says 5 star so it is almost free.
Both are guessing.
I guess too.
I just show the guess.
Watts per ton is not a lab sticker.
Star rating moves the rupee a lot.
Set point on the remote moves it again.
This post is the summer question with numbers you can change.
Why this question shows up every April
Hall is closed, bedroom AC starts at 10 pm, off at 6 am.
That is 8 hours if nobody cheats and leaves it till 8.
Cousin wants the monthly hit before he buys a second machine.
I dont walk into a showroom PDF.
I open AC running cost calculator.
Tonnage 1.5.
Hours 8.
Days 30, or 31 if I am feeling precise, I usually put 30.
Unit rate from last bill, say 8.
Assumed watts per ton, the tool default sits near 800.
1.5 times 800 is 1,200 W.
That is 1.2 kW if it were a heater running flat.
AC is not a heater running flat.
Inverter machine cycles down.
Old fixed speed machine gulps, stops, gulps.
So 1,200 W is a average-ish story, not a oscilloscope.
I say that out loud so nobody frames the result.
Then the units math is simple.
1,200 watts times 8 hours times 30 days, divide by 1,000.
That is 288 units.
288 times ₹8 is ₹2,304.
That is the rupee I quote for one AC, one room, that usage.
Second AC in the other room is another 288 if it also does 8 hours.
Fridge is extra, lights are extra.
People hear 2,304 and think that is the whole house.
It is not.
It is the AC slice if the watt guess is fair.
Watts per ton is a guess, I say it again
800 W per ton is a middle.
Some 5 star inverter in a closed room sits lower, maybe 600 to 700 on a mild night.
Some old 1.5 ton from 2012 sits 1,000 plus when the compressor is on.
If I put 1,000 W per ton, 1.5 ton is 1,500 W.
8 hours, 30 days, 360 units.
At ₹8 that is ₹2,880.
Same hours.
Different machine.
If I put 600 W per ton, 1.5 ton is 900 W.
216 units.
₹1,728 at 8.
See the spread.
₹1,728 to ₹2,880 for the same 8 hour story.
That is why I refuse a single official AC rupee.
I dont have your ISEER printed on this page.
You can drop assumed watts in the box if you know your star.
Higher star, usually lower watts.
Not magic.
Dirty filter, west facing glass, 18 degree set point, those push watts back up.
I tell cousin, start at 800.
If last summer the bill jumped about 280 units when the AC season started, your real draw is near that 288 story.
If it jumped 400, you are closer to the thirsty machine, or you ran more than 8 hours, or there is a second unit.
Match the bill, then keep that watts per ton for next month.
The picture is 1.5 ton, 8 hours, 30 days, ₹8, 800 W per ton.
Units near 288.
Money near 2,304.
Change one box and the story moves.
I also run the same hours on power consumption calculator if I already know watts from a sticker.
Sticker might say 1,380 W or 1,050 W.
That is input power at a test point, not always the night average.
Still better than a random 1,500.
1.5 ton is cooling capacity, not 1,500 watts.
People mix ton and kW.
I used to also.
1 ton cooling is about 3.5 kW of cooling, not 1 kW of electric.
Electric is less because it is a heat pump, not a kettle.
Dont type 3500 W unless you enjoy a panic bill.
Eight hours is a polite number
8 hours assumes you switch off.
I dont.
Weekend nap, 2 pm to 6 pm extra.
Guests, AC in the hall.
Those hours add.
9 hours instead of 8 is 12.5 percent more units.
288 becomes 324.
Money 2,304 becomes 2,592 at the same 8 rupee.
24 hours is a different planet.
I have a relative who leaves it on for the dog.
Units climb.
The tool will do 24 if you type 24.
I just ask, is that true.
26 degree vs 18, the box cannot see the remote.
Lower set point, longer compressor work, more units.
I bump watts per ton in my head when someone says they sleep at 18.
Ceiling fan plus AC at 26 often cheaper than AC at 20 with no fan.
Not a lab paper.
Just what I see on bills.
Stabilizer is a few watts.
I ignore it unless we are counting every rupee for a hostel study.
Rajasthan May, two ACs, fridge, I have seen houses near 400 units.
I wrote summer bill around 400 units in Rajasthan for that pile.
This page is one machine.
Rate still from last bill, see I dont know my unit rate if that box is empty.
Then put the AC units into electricity bill calculator with the rest of the house.
Dont expect the AC tool to print the full DISCOM bill.
It will not.
What I type, and the misses I see
Tonnage, 1.5, not 15, not 0.15.
Hours a day, the real ones.
Days in the month.
Unit rate.
Assumed watts per ton last.
If result looks like a rent, I check 8,000 W per ton.
Extra zero.
If result looks like a tea stall, I check 80 W per ton.
Missing zero.
City vs dry weather, I dont have a humidity box.
Humid coast, machine works harder for the same 26.
I nudge watts up a little.
Dry night, maybe the default is fine.
Window AC vs split, window often thirstier for the same ton.
I nudge again.
I dont collect model numbers.
This is a cousin call, not a service visit.
Inverter vs non inverter, the default 800 leans inverter-ish.
Non inverter, I start near 1,000.
Your sticker still wins.
If you only run 15 days in a month, put 15 in days.
Dont put 8 hours and then mentally halve, then also put 15 days, and halve again.
I watched a guy do that.
He thought AC is free.
It was not.
Generator or inverter backup, this rupee is grid rupee.
Fuel for a petrol generator is a different tool mood, more like fuel cost if you know litres.
I dont mix those in one result.
Solar day units, AC at night still hits the grid unless you have storage.
Type honest hours on grid.
I keep saying estimate, not official, because the board will bill whatever the meter says.
Meter is the adult.
This page is the preview.
If preview and meter fight by 20 units, I shrug.
If they fight by 200, hours were wrong, or watts were fantasy, or there is another load.
Fridge plus water heater can eat a quiet 80 to 120 units without any AC.
Add those on the power tool.
Then you stop blaming only the 1.5 ton.
That is the useful end of the summer argument.
Not a speech about the digital anything.
Just 288 units as a start, then move the watts till it matches your house.