Energy & power
Power, consumption and cost: appliances, kilowatt-hours, solar output and heating requirements. 26 tools, including Amperage Calculator, Appliance Energy Cost Calculator, Appliance running cost calculator and Battery life calculator. All free, with no account and nothing to install.
Amperage CalculatorConvert a load in watts and a supply voltage into the current drawn in amps.Appliance Energy Cost CalculatorTurn any appliance's wattage and daily use into a daily, monthly and yearly running cost in your currency.Appliance running cost calculatorEstimate what an appliance costs to run per day, month and year.Battery life calculatorEstimate how long a battery lasts from its capacity and the load current.Electric field calculator (point charge)The electric field and potential around a point charge: E = k·q / (εᵣ·r²) and V = k·q / (εᵣ·r). Enter the charge, the distance and the surrounding medium — the dielectric weakens the field, water by about 80× — and see the values with SI prefixes plus a field-line diagram.Generator size calculatorEstimate the generator size you need from the wattages of your appliances.Heat Loss CalculatorAdd up the conductive heat loss through walls, windows, doors and roof from their area and R- or U-value.Heat pump savings calculatorWhat a heat pump costs to run against your current boiler, from your own fuel bill: the heat you actually need, the electricity a given SCOP would draw, the yearly difference and the payback. Plus the one number that decides it — the electricity price above which the heat pump stops being cheaper.Heating BTU CalculatorEstimate the heating power in watts and BTU needed to heat a room based on its area and climate.Home Energy Audit CalculatorEstimate your home's annual energy use, cost, intensity and HVAC share from its shell and major appliances.HVAC Sizing CalculatorEstimate the heating and cooling load of a room in BTU/hr, kW and tons from its area, climate and insulation.Insulation CalculatorFind the recommended R-value for your climate and component, and how much insulation you still need to add.kWh to CO₂ calculatorEstimate the CO₂ emissions from electricity use and a grid emission factor.Light Bulb Savings CalculatorCompare LED, incandescent and CFL bulbs on yearly energy plus replacement cost, and see your LED savings.Power dissipation calculatorCompute the power dissipated by a resistor from current and resistance (P = I²R).Power Factor CalculatorCompute power factor, apparent and reactive power, and PF-correction capacitance.RC time constant calculatorCompute the RC time constant (τ = R × C) of a resistor-capacitor circuit.Solar battery size calculatorEstimate the battery capacity you need from daily energy use and days of autonomy.Solar panel calculatorEstimate how many solar panels you need from your daily energy use.Transformer turns ratio calculatorCompute a transformer's turns ratio from its primary and secondary voltage.TV Size CalculatorFind the recommended TV screen size for your viewing distance, with a comfortable range.Voltage divider calculatorCompute the output voltage of a two-resistor voltage divider.Voltage drop calculatorEstimate the voltage drop in a copper cable from its length, current and cross-section.Water Heater Size CalculatorEstimate the recommended storage water heater capacity for your household size.Wire Gauge CalculatorGet a rough minimum copper wire cross-section for a given current draw.Wire resistance calculatorCompute the resistance of a wire from its length, cross-section and material.