FreeTools Labs Glossary
Electricity and energy costs
Learn why kW describes power and kWh describes energy, and how power, runtime and price produce estimated energy costs.
Relevant tool
Electricity & energy cost calculator
Calculate appliance energy use, standby and electricity costs.
Open Electricity & energy cost calculator →Energy cost combines device power with operating time to obtain kilowatt-hours, then applies the price per kWh only when a cost is requested.
Functions and inputs
Six paths cover regular device cost, power and time, known energy, standby use, multiple devices and a device comparison. Power accepts mW/W/kW, energy Wh/kWh and duration minutes, hours or continuous days.
Calculation model
The energy and cost paths make the power-to-energy conversion explicit before multiplying by the entered tariff: E(kWh) = P(W) ÷ 1000 × t(h); cost = E(kWh) × price/kWh.
How the calculator model works
A price per kWh is always user-entered. Power-and-time can show energy with no price; other price-dependent paths wait for a price, while zero remains a valid numerical price. Regular use uses entered hours/day, days/week and weeks/year; the explicit 24/7 path uses 8,760 hours.
Checked examples
These checked values illustrate a short use, a recurring annual use and continuous operation: 1,000 W × 2 h = 2 kWh; 2 × 0.30 = 0.60. 100 W × 8 h × 7 × 52 = 291.2 kWh; × 0.30 = 87.36; 87.36 ÷ 12 = 7.28. 100 W × 8,760 h = 876 kWh.
Units, display and interpretation
mW, W and kW describe power, while Wh and kWh describe accumulated energy; monthly cost is an annual average when that mode provides one: mW/W/kW · Wh/kWh · min/h/d · entered currency format; monthly average = annual ÷ 12.
Scope and limits
The result has no tariff lookup, supplier recommendation, standing charge, tier, tax, grid fee, exchange-rate or CO₂ model. Constant entered power and time are not a consumption forecast or a utility bill.