Formula and practical context.
energy (kWh) = power (kW) × hours/day × days; cost = energy × price/kWhPower is the appliance rating, operating time is hours per day, days is a whole-number period, and price is the chosen currency per kWh.
Formula, variables, and method
energy (kWh) = power (kW) × hours/day × days; cost = energy × price/kWh. Power is the appliance rating, operating time is hours per day, days is a whole-number period, and price is the chosen currency per kWh. The result estimates electrical energy use and its variable energy charge from power, operating time, days, and unit price. Start by identifying what each entered number represents and whether it is a measured value, a specification, or an assumption. Convert units before combining quantities, preserve full precision through intermediate steps, and round only the displayed result. Convert watts to kilowatts when necessary, multiply kW by hours per day and days, then multiply kWh by the entered price. This sequence makes the output reproducible and helps expose a misplaced unit or decimal point before it affects a decision.
Worked example and independent check
A 1.5 kW appliance used for 4 hours per day over 30 days consumes 180 kWh; at 0.20 per kWh the energy charge is 36. To check the example independently, write the formula first, substitute the values with their units, and complete one operation at a time. Compare the order of magnitude with a familiar reference rather than accepting a formatted result automatically. Convert watts to kilowatts when necessary, multiply kW by hours per day and days, then multiply kWh by the entered price. If a second method or inverse calculation is available, use it to recover an original input. Small differences from hand calculation should come only from displayed rounding, not from a different definition.
Units and result interpretation
Watts are converted to kilowatts before multiplying by hours. A kilowatt-hour is energy, while a kilowatt is instantaneous power. The result estimates electrical energy use and its variable energy charge from power, operating time, days, and unit price. A unit is part of the quantity, not a label added after the arithmetic. Keep decimal and binary prefixes, temperature scales, elapsed-time units, and electrical prefixes explicit. When comparing two scenarios, change one assumption at a time and retain the same unit convention. The result describes only the relationship named by this calculator; it does not automatically establish capacity, safety, compatibility, quality, or compliance.
Validation and boundary cases
Power, hours, days, and price must be finite and nonnegative; hours per day cannot exceed 24 and the day count must be a whole number. Blank values, malformed text, non-finite numbers, impossible ranges, zero divisors, and unsupported combinations receive an explicit message rather than a silent fallback. Boundary values are checked before the formula runs. If an input comes from a specification sheet, weather report, network plan, or measurement instrument, confirm its definition and precision. A syntactically valid value can still be unsuitable for the real situation, so inspect the assumptions alongside the result.
Assumptions, privacy, and practical limits
Bills may also include fixed charges, taxes, time-of-use rates, demand charges, tiering, power factor, and appliance duty cycles. All entered values are processed in the browser and are not sent to a calculation service. Use the result as a transparent estimate or transformation, keep the source values with any saved result, and consult the linked authoritative material for definitions and applicability. For safety-critical, health-adjacent, security, network, chemical, or electrical work, verify the result with current standards, official warnings, qualified professionals, and appropriate test equipment.
Check assumptions and sources.
Bills may also include fixed charges, taxes, time-of-use rates, demand charges, tiering, power factor, and appliance duty cycles.
Common questions.
What does the Electricity Calculator do?
Estimate appliance energy use and variable electricity cost from power and operating time.
How can I check the result?
Convert watts to kilowatts when necessary, multiply kW by hours per day and days, then multiply kWh by the entered price.
Which units and assumptions matter?
Watts are converted to kilowatts before multiplying by hours. A kilowatt-hour is energy, while a kilowatt is instantaneous power. Bills may also include fixed charges, taxes, time-of-use rates, demand charges, tiering, power factor, and appliance duty cycles.
Are the entered values sent or stored?
No. The calculation runs locally in your browser and FigureNest does not send or store calculator inputs.