Electricity Calculator

  • 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.
  • Photon Energy Calculator
    Calculate photon energy from wavelength or frequency using E = hf = hc/λ. Get results in joules, electronvolts, frequency (THz) and wavelength (nm).
  • Solar Panel Tilt Angle Calculator
    Find the optimal solar panel tilt angle from your latitude. Get year-round, summer, and winter tilt settings to maximize energy production.
  • Solar Charge Controller Sizing Calculator
    Size your solar charge controller in amps from panel wattage and battery voltage. Includes a 1.25 safety factor for MPPT/PWM controller selection.
  • HP to kW Calculator
    Convert horsepower (HP) to kilowatts (kW) instantly. Enter any HP value to get the equivalent power in kW using kW = HP × 0.7457.
  • 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.
  • kW to HP Calculator
    Convert kilowatts (kW) to mechanical horsepower (hp) instantly. Uses HP = kW / 0.7457 for accurate power conversion of engines and motors.
  • Watts to kVA Calculator
    Convert watts (W) to kilovolt-amps (kVA) using the power factor. Fast, accurate W to kVA conversion for AC electrical systems.
  • 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.
  • 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 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.
  • 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.
  • 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.
  • LED Wire Voltage Drop Calculator
    Calculate the voltage drop in wires feeding an LED or LED strip. Enter current, length, wire area and material to find loss, voltage at the LED and power waste.
  • 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.
  • 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).
  • Voltage Drop Percentage Calculator
    Calculate voltage drop percentage (VD%) from source voltage and voltage drop. Check if your circuit meets the common 3% / 5% limits instantly.
  • 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.
  • 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.

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