Electricity Bill Calculator
Enter slab rates, fixed charge, fuel adjustment and tax to see a tiered electricity bill with a slab-by-slab breakdown.
Step-by-step
- Enter valid values to begin.
Amounts are in your own currency. Slab limits are cumulative kWh per billing period (slab 2 covers kWh above limit 1 up to limit 2, and so on); slab 4 has no upper limit. A fixed charge entered per month is charged once per bill, and one entered per day is multiplied by the billing days. Tax is applied to energy + fixed + fuel adjustment; some tariffs tax differently, so check your utility’s schedule. Monthly and annual forecasts scale this bill by days (365/12 days per month) and assume the same consumption repeats, which overstates or understates slab costs if your use is seasonal.
Electricity Bill Calculation: Reading a Tiered Tariff Line by Line
Core Engineering Principles
A bill looks like one number, but it is a stack of separate charges, and you can only find the savings if you pull the stack apart. The energy charge is the part the meter measures: kilowatt-hours multiplied by a rate. Most residential tariffs use blocks: the first kilowatt-hours are cheap and each higher slab costs more. Only the kWh inside a slab are charged at that slab’s rate, so crossing a limit never reprices earlier usage. The fixed charge pays for the line and meter and is owed whether the lights are on or not. A fuel adjustment tracks generation cost, per kWh or as a percentage of the energy charge.
The number that matters for decisions is the marginal rate, not the average. If your usage ends in the top slab, the next kilowatt-hour costs the slab rate plus fuel adjustment plus tax, often well above your average cost per kWh, and and that is the figure to use when judging an LED retrofit or a shut-off habit. Multiplying one bill by twelve ignores seasons: slabs reset every period, so a hot month can reach slab 4 while a mild month never leaves slab 1. Run each season separately and add the results.
Bill = (Energy + Fixed + Fuel) × (1 + tax) • Average = Bill / kWh
NEC & Standard References
Tariffs come from the regulator and the utility’s rate schedule, not from an engineering standard, so read the schedule. Standards govern the measurement behind the bill: IEC 62052-11 gives the general requirements for electricity metering equipment, IEC 62053-21 covers static meters for active energy in accuracy classes 1 and 2, and IEC 62053-22 covers classes 0.2S and 0.5S for larger customers. In North America ANSI C12.1 and ANSI C12.20 cover meter code and accuracy. A class 1 meter is about ±1% at reference conditions. Check the adopted edition.
1. Slab 1: 200 × 0.10 = 20.00. Slab 2: 300 × 0.14 = 42.00. Slab 3: 150 × 0.18 = 27.00. Energy charge = 89.00.
2. Fuel adjustment = 650 × 0.012 = 7.80, fixed = 10.00, so the subtotal is 106.80.
3. Tax = 106.80 × 8% = 8.54, giving a total bill of 115.34.
4. Average cost = 115.34 / 650 = 0.1775 per kWh, but the marginal cost is (0.18 + 0.012) × 1.08 = 0.207 per kWh.
5. Daily cost = 3.84; the annual forecast is 115.34 × 365 / 30 = 1,403.35.
- Check the slab limits per period. A 60-day bill may double the limits or may not.
- Use the marginal rate for savings. Cutting 50 kWh in slab 3 saves 10.37, not 50 times the average of 0.1775.
- Fixed charges never shrink with efficiency. Exclude them from payback figures.
- Estimated readings distort slabs. A catch-up reading can push one bill into the top slab.
- Taxes may not apply uniformly. Confirm which charges your utility taxes.