Electricity Calculator

  • Generator Size Calculator
    Calculate the right generator size in watts. Add running watts plus the largest starting surge, with a safety margin, to size your generator correctly.
  • kVA Calculator
    Calculate apparent power in kVA from voltage and current for single-phase and three-phase circuits. Free, instant kVA calculator with formula.
  • Device Power Consumption Cost Calculator
    Calculate how much electricity a device costs to run. Enter watts, hours per day, days and your price per kWh to get total and daily running cost.
  • Volts to Watts Calculator
    Convert volts to watts instantly. Enter voltage (V) and current (A) to calculate electrical power in watts using P = V × I.
  • Heat Pump COP Calculator
    Calculate a heat pump's Coefficient of Performance (COP) from heat output and electrical input in kW. Free, instant efficiency calculator.
  • Solar Panel Output Calculator
    Estimate your solar panel system's daily, monthly and annual energy output (kWh) from system size, peak sun hours and performance ratio.
  • Appliance Running Cost Calculator
    Calculate the daily, monthly and yearly running cost of any appliance from its wattage, hours of use and your electricity rate per kWh.
  • Smart Home UPS / Battery Backup Runtime Calculator
    Estimate how long your UPS or home battery will power your devices. Enter capacity (Wh), load (W), inverter efficiency and depth of discharge to get runtime.
  • Solar Battery Home Backup Sizing Calculator
    Size a home solar battery backup. Enter daily energy use, backup days, and depth of discharge to find the battery capacity (kWh) you need.
  • Smart Home Device Power Consumption Calculator
    Estimate the yearly cost, energy and CO2 of standby (vampire) power from smart home devices. Enter standby watts and your electricity rate.
  • Smart LED Bulb Energy Savings Calculator
    Calculate how much you save each year by switching old bulbs to energy-efficient smart LEDs. Enter wattage, hours, bulbs and electricity cost.
  • Smart Thermostat Savings Calculator
    Estimate how much money a smart thermostat can save you each year on heating and cooling. Enter your annual energy cost and savings percentage.
  • Resistor Color Code Calculator
    Decode a 4-band resistor color code into ohms with tolerance. Select each band color to get resistance and the min/max value range instantly.
  • Heating Degree Days (HDD) Calculator
    Calculate Heating Degree Days (HDD) from your daily high, low and base temperature. Estimate heating demand using HDD = max(0, Tbase − mean temp).
  • Cooling Degree Days (CDD) Calculator
    Calculate cooling degree days (CDD) from daily high and low temperatures and a base temperature. Estimate building cooling energy demand fast.
  • Joule Heating Calculator
    Calculate the heat energy from Joule heating using Q = I²Rt. Enter current, resistance and time to find heat in joules, plus power and voltage.
  • kVA to Amps Calculator
    Convert kVA to amps for single-phase and three-phase systems. Enter apparent power and voltage to get current in amperes instantly.
  • Watt-Hours Calculator
    Convert battery amp-hours (Ah) and voltage (V) to watt-hours (Wh) and kilowatt-hours (kWh) instantly. Free Wh = Ah × V energy calculator.
  • Kirchhoff Voltage Divider Calculator
    Calculate the output voltage of a two-resistor voltage divider using Vout = Vin·R2/(R1+R2). Also finds loop current and total power dissipated.
  • Transformer Turns Ratio Calculator
    Calculate transformer turns ratio from primary and secondary voltage. Find secondary turns and current using Np/Ns = Vp/Vs = Is/Ip. Step-up or step-down.
  • Resistivity Calculator
    Calculate the electrical resistance of a wire from its resistivity, length, and cross-sectional area using R = ρL/A. Free, instant, accurate.
  • Inductor Energy Calculator
    Calculate the magnetic energy stored in an inductor with E = ½·L·I². Enter inductance in henries and current in amperes to get energy in joules.
  • Power and Heat Flow Conversion Calculator
    Convert power and heat-flow-rate units: watt, kilowatt, BTU/h, calories per second, ergs, horsepower variants and more, using exact watt-based factors.
  • MPGe Calculator
    Calculate MPGe (miles per gallon equivalent) for electric vehicles from miles driven and kWh used, using the 33.7 kWh/gallon standard.

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