All worked examples below use explicitly chosen inputs. They are not measured household averages, utility quotes, or guaranteed savings.
Start with kWh, then check the units
Find the electricity usage line for the current billing period. It should show kilowatt-hours, usually written as kWh. This is energy used over time; kW describes power at a moment. A 1,000-watt appliance running at that power for one hour uses 1 kWh.
Next, look for charges labeled per kWh. A bill might show $0.125/kWh or 12.5¢/kWh. Those are the same rate. Our calculators label the rate field in cents, so enter 12.5, not 0.125. Entering dollars into a cents field makes the estimate 100 times too small.
Reference: EIA: Measuring electricity
A sample bill: 18¢ and 20¢ can both be correct
The following is an invented teaching example, not a utility tariff. Assume 600 kWh of use, one flat rate, no taxes, and no credits. Both the supply and delivery charges increase with each additional kWh.
| Charge | How it is calculated | Amount |
|---|---|---|
| Supply | 600 kWh × $0.12 | $72.00 |
| Delivery | 600 kWh × $0.06 | $36.00 |
| Fixed customer charge | Same amount each month | $12.00 |
| Total | Energy charges + fixed charge | $120.00 |
- Use 18¢/kWh to estimate the added energy charge for one more appliance in this example.
- Use 20¢/kWh to describe what this household paid per kWh overall during this billing period.
- Running an appliance less does not remove the $12 fixed charge.
What to include on your own bill
Charge names differ by utility. Read how each line is calculated, not just its label. A fuel adjustment or rider may be assessed per kWh; a service charge may be fixed. Include applicable variable charges when estimating extra use. Leave past-due balances, late fees, deposits, and unrelated services out of an electricity-rate calculation.
Some bills mix fixed and usage-based delivery charges. If the bill does not show enough detail, use your current rate schedule or ask the utility which charges change when you use one additional kWh. Our calculator applies one energy rate; it does not separately calculate percentage taxes, demand charges, minimum bills, or bill credits.
Time-of-use and tiered plans need another step
With time-of-use pricing, the relevant rate depends on when you run the appliance. EIA explains that some utilities vary consumer prices by time of day. Calculate each period separately instead of applying the cheapest rate to every hour.
For example, 4 kWh at an illustrative 10¢ off-peak rate plus 2 kWh at 30¢ costs $1.00. That is an effective 16.67¢/kWh for those 6 kWh. If your tariff has tiers, extra usage can fall into a different tier from the electricity you already used. The relevant extra-use price may therefore differ from your monthly average.
Reference: EIA: Factors affecting electricity prices
If the bill rose, compare usage per day first
Separate a price change from a usage change. In a simple example, 600 kWh over 30 days and 660 kWh over 33 days both equal 20 kWh per day. The larger second total does not mean daily consumption rose.
Compare current-period charges, billed days, kWh per day, and the applicable rates with a previous bill. Check whether readings are actual or estimated and whether an adjustment is included. This gives you a more useful starting point than guessing which appliance is responsible. A state average can help with context, but it cannot diagnose your bill or replace your utility’s tariff.
Sources & calculation notes
References checked 2026-10-08. Example arithmetic is calculated by HomeWattCheck. Article review dates are separate from the EIA data period displayed in our calculators.
Each calculator states its scope beside the result. Appliance tools estimate electricity at one rate; the time-of-use comparator includes two price periods and entered fixed fees. Complex tariffs may need additional calculations. State averages describe reported residential revenue per kWh, not your utility’s offer. See our data sources and methodology or state rate comparison.