Estimate an electricity bill from your expected kWh, a flat variable rate, and the fixed fees or other charges you enter. Use the actual number of billing days, choose a per-bill or daily fixed charge, and add any known credits to see an itemized scenario.
Make sense of your bill
Build your electricity bill estimate
Start with your expected kWh and variable rate, then add the fixed fees and other amounts you know. See each part of a flat-rate bill scenario.
Read the bill breakdown
The variable energy charge is your entered kWh multiplied by the rate per kWh. A fixed charge for the whole bill is added once; a daily fixed charge is multiplied by your billing days. Other charges are a single total for this period, and entered credits are subtracted once. Even with zero electricity use, fixed and other entered charges can remain.
Changing the number of days does not rescale the total kWh you entered. It changes daily averages and any daily fixed charge. For month-to-month comparisons, check the actual billing dates and kWh per day rather than assuming every month is the same length.
Choose the right rate and adjustments
Use a variable electricity rate that excludes fixed fees. An effective rate calculated by dividing a previous total bill by kWh may already include those fees. Adding them again can double-count costs. Enter taxes or surcharges under other charges only when you know their actual amounts and they are not already included in the rate.
This tool does not automatically calculate tax rules, time-of-use schedules, usage tiers, demand charges, minimum bills, or solar export credits. A negative net result means your entered credits exceed the modeled charges; it does not establish whether a provider will carry the credit forward or issue a refund. Compare the scenario with the details of your own tariff and bill.
For individual appliances and buying decisions, try the Electricity Cost Calculator or Appliance Running Cost Comparison.
Purpose
Model one flat-rate electricity bill from total period kWh, a variable price, entered fixed fees, other charges, and credits. General principles; no regional tariff, tax, or account data is fetched.
Inputs
Total electricity use for the billing period: nonnegative kWh; decimals accepted.
Billing days: a whole number of at least 1.
Variable price: nonnegative currency/kWh or cents/pence per kWh.
Optional fixed charge: nonnegative major-currency amount for the bill or per day.
Optional other charges and credits: nonnegative major-currency totals for this bill. Credits are subtracted; blank optional amounts count as zero.
All amounts must use the same selected currency. Extremely large values or combined charges are rejected.
Units
kWh for the whole billing period; whole billing days; currency/kWh or cents/pence per kWh; major-currency fees and credits. USD, CAD, AUD, EUR, and GBP are labels only, with no foreign-exchange conversion. Rate-unit switching and fixed-fee period switching preserve the current scenario.
Currency
USD
Formula / model
Variable energy charges = period kWh × price per kWh.
Fixed charge = entered per-bill amount, or entered daily charge × billing days.
Subtotal = variable energy charges + fixed charge + other entered charges.
Net result = subtotal − entered credits.
Daily kWh = period kWh / billing days.
Daily cost equivalent = net result / billing days.
If the rate is entered in cents or pence, divide it by 100 first. All fee and credit inputs are in the major currency. A negative net result is an estimated credit balance, not an amount due. Computation precedes display rounding; negligible floating-point cancellation around zero is normalized.Model version
monthly-bill-v1.0.0 / shared-electricity-model-v1.2.0
Assumptions & limitations
One flat variable price applies to all entered energy in the chosen period. Total kWh is supplied by the user; changing billing days does not rescale it. A per-bill fixed fee is added once; a daily fixed fee scales with the entered days. Zero usage can still incur fixed and other charges.
No taxes, surcharges, demand charges, time-of-use prices, usage tiers, minimum bills, export compensation, or account adjustments are added automatically. Enter only known extra amounts not already included elsewhere. A total bill divided by kWh may include fixed costs and should not be used as the variable rate while adding those fixed costs again.
Credits are a user-entered scenario, not a determination of eligibility or a promised refund. Daily cost is an average of the net modeled bill, not a marginal electricity rate. Different utility rounding and billing rules can change actual amounts; displayed line items may differ slightly from the displayed total due to rounding.
Defaults are illustrative, not typical household use, measured consumption, or current market tariffs. Currency changes labels only. Small nonzero amounts below 0.01 display as less than 0.01 rather than zero. Inputs are calculated locally in the browser and are not sent or stored by this tool.
Worked example
Illustrative 30-day scenario: 600 kWh at USD 0.20/kWh, USD 15 fixed fee for the bill, USD 5 in other entered charges, and no credits.
Energy charge = 600 × 0.20 = USD 120.
Net bill estimate = 120 + 15 + 5 − 0 = USD 140.00.
A daily fixed fee of USD 0.50 over the same 30 days also gives USD 15. Over 31 days it gives USD 15.50, while the entered total usage remains 600 kWh.
If usage is zero, the original fixed and other charges give USD 20.00.
Adding USD 10 in credits to the original scenario gives USD 130.00. Adding USD 150 in credits gives an estimated USD 10.00 credit balance rather than a payment due.
Sources
Virginia Cooperative Extension — ENERGY SERIES: Estimating Appliance and Home Electronic Energy Use, publication 2901-9014, February 26, 2020. Supports multiplying kWh by a variable electricity rate. Fixed-fee, extra-charge, and credit arithmetic are the explicitly documented scenario model above; historical tariffs and appliance examples are not defaults. https://www.pubs.ext.vt.edu/2901/2901-9014/2901-9014.html
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