The exact formula — from ISEER to rupees. Includes the 1,600-hour reality check, slab-rate awareness, hidden taxes guide, and an interactive formula builder.
Adjust variables — the formula solves itself in real-time
AC Tonnage
Star Rating
Live Formula
Daily Cost
₹69.99
Monthly
₹1,176
Annual Total
₹14,110
Three formulas — from simple to precise. Use the one that matches your data.
Use when you only know tonnage and star rating
Annual Cost (₹) =
Label Units × (Your Hours ÷ 1,600) × Rate (₹/unit) × 1.12
The 1.12 factor accounts for taxes and fixed charges. Accuracy: ±15%
Use when you know ISEER and usage hours
Step 1: Rated Wattage (W) =
(Tonnage × 3,517) ÷ ISEER
Step 2: Annual Units (kWh) =
Wattage × 0.85 × Hours/Day × Days/Year ÷ 1,000
Step 3: Annual Cost (₹) =
Annual Units × Incremental Rate × 1.12
The 0.85 factor = inverter AC average load factor. Use 1.0 for fixed-speed ACs. Accuracy: ±8%
Use when you have a smart meter or energy monitor
Annual Cost (₹) =
Measured kWh/Day × Days/Year × Incremental Slab Rate + Fixed Charges + Taxes
Requires a smart plug or energy monitor (e.g., Wipro Smart Plug). Accuracy: ±2%
Key Variable: ISEER vs. EER
Always use ISEER (not EER) for annual calculations. ISEER accounts for seasonal temperature variation across India's climate zones. Using EER will underestimate your annual cost by 15–25% because EER is measured at a single temperature (35°C) and doesn't reflect the full cooling season.
Click any element on the label to understand exactly what it means for your bill.
Bureau of Energy Efficiency
STAR LABEL
Brand / Model
XYZ Brand · Model AC-1500
ISEER
4.10
Annual Units
762 kWh
Valid: 2026 · IS 1391
Annual Units (kWh/Year)
This is the KEY number. BEE calculates this at exactly 1,600 hours/year (~4.4 hrs/day). If you use your AC for 8 hrs/day, multiply this number by 1.82 to get your real annual consumption.
The 1,600-Hour Adjustment
BEE's "Annual Units" on the star label is calculated at exactly 1,600 hours/year — roughly 4.4 hours/day for 365 days. Most Indian households use their AC for 6–12 hours/day in summer.
The Label Lie: A 5-star AC showing "762 units/year" on the label will actually consume 1,387 units/year if you run it 8 hours/day for 6 months. The label is not wrong — it's just based on a different usage assumption than yours.
Annual Usage Hours
5★ Inverter
3★ Normal
You Save
500 hrs
~1.4 hrs/day · Occasional use
549 u
₹4,392
703 u
₹5,624
154 u
₹1,232/yr
1,000 hrs
~2.7 hrs/day · Light use
762 u
₹6,096
976 u
₹7,808
214 u
₹1,712/yr
1,600 hrs
~4.4 hrs/day · BEE standard
BEE Label Basis1,219 u
₹9,752
1,562 u
₹12,496
343 u
₹2,744/yr
2,000 hrs
~5.5 hrs/day · Moderate use
1,524 u
₹12,192
1,952 u
₹15,616
428 u
₹3,424/yr
2,920 hrs
~8 hrs/day · Heavy use
2,225 u
₹17,800
2,851 u
₹22,808
626 u
₹5,008/yr
4,380 hrs
~12 hrs/day · Very heavy use
3,338 u
₹26,704
4,277 u
₹34,216
939 u
₹7,512/yr
The DU Tech Adjustment Formula
Your Real Annual Units = Label Units × (Your Hours/Day × Your Days/Year) ÷ 1,600
Example: Label says 762 units. You use 8 hrs/day for 180 days = 1,440 hrs.
Real consumption = 762 × (1,440 ÷ 1,600) = 686 units. At ₹8/unit = ₹5,488/year.
A complete step-by-step walkthrough — 8 hours/day, 180 days/year, ₹8/unit, Mumbai household.
Find Cooling Capacity
1 Ton = 3,517 W of cooling capacity
1.5 Ton × 3,517 W/Ton
= 5,275 W
Calculate Rated Wattage
Wattage = Cooling Capacity ÷ ISEER
5,275 W ÷ ISEER 4.10
= 1,286 W
Apply Inverter Factor (0.85)
Inverter ACs run at ~85% of rated wattage on average
1,286 W × 0.85
= 1,093 W avg
Calculate Annual Hours
Typical Indian summer usage: May–October
8 hrs/day × 180 days
= 1,440 hrs/year
Calculate Annual Units
kWh = Watt × Hours ÷ 1,000
1,093 W × 1,440 hrs ÷ 1,000
= 1,574 kWh
Calculate Raw Cost
Use your actual slab rate for accuracy
1,574 kWh × ₹8/unit
= ₹12,592/year
Add Hidden Charges (+12%)
Taxes, duty, fixed charges add ~10–15%
₹12,592 × 1.12
= ₹14,103/year
Final Answer
Annual Units
1,574 kWh
actual consumption
Raw Bill
₹12,592
before taxes
Total Bill
₹14,103
incl. all charges
Monthly Average
₹1,175
spread over 12 months
Model: 1.5T 5-Star Inverter AC · ISEER 4.10 · 8 hrs/day · 180 days/year · ₹8/unit · Mumbai tariff with 12% additional charges
Two hidden multipliers that the BEE label never mentions — slab rates and additional charges.
The Slab Trap: If your household already consumes 300 units/month before the AC, every AC unit is billed at the highest slab rate — not the average rate. This can add 30–50% to your effective AC cost vs. the label's assumption.
Delhi (BSES)
Mumbai (Adani)
Bangalore (BESCOM)
Chennai (TANGEDCO)
These charges add 10–15% to your raw electricity cost — and the BEE label accounts for none of them.
Fixed/Demand Charge
₹50–₹200/monthA flat monthly charge regardless of consumption. Covers grid maintenance costs.
Adds ₹600–₹2,400/year
Electricity Duty (ED)
5–15% of billState government tax on electricity consumption. Varies by state — Maharashtra charges 15%, Delhi 5%.
Adds 5–15% to raw bill
Fuel Adjustment Charge (FAC)
₹0.10–₹1.50/unitPassed on by utilities when fuel costs rise. Changes quarterly. Often not shown on the label.
Adds ₹0.10–₹1.50/unit
Meter Rent
₹10–₹50/monthMonthly rental for the electricity meter. Small but consistent.
Adds ₹120–₹600/year
Wheeling Charges
₹0.50–₹2.00/unitCost of transmitting electricity through the grid. Included in most tariffs but sometimes listed separately.
Adds ₹0.50–₹2.00/unit
Total Hidden Cost Estimate
Step 1: Check Last Month's Bill
Find your total units consumed before AC season. This is your 'base consumption'.
Step 2: Find Your Current Slab
Look at the slab table for your state. Find which slab your base consumption falls in.
Step 3: Use the Next Slab Rate
Every AC unit you add will be billed at the NEXT slab rate — not your current average rate. Use this for accurate AC cost calculation.
Enter your AC model, usage hours, and city — our calculator handles the slab rates, taxes, and ISEER automatically.