Electricity & Energy Calculators

See what each appliance adds to your bill — pick a common preset or enter your own watts.

Turn kilowatt-hours and a time span into average watts — the power-versus-energy conversion.

Amps from watts and volts — the breaker-and-wire-sizing question, with the 80% circuit rule.

Convert volts to amps by either route — Ohm's law from a resistance, or power from a load in watts.

Watts from amps and volts — what a circuit or outlet can actually power, safely.

Estimate daily, monthly, and yearly production from system size, sun hours, and losses.

How many panels to cover your usage — by monthly kWh, sun hours, and panel wattage.

Build your monthly bill from usage, rate, fixed charges, and tax — and the true all-in $/kWh.

Energy and a time span to average current — the two-step kWh → watts → amps conversion.

Convert a current draw to kilowatt-hours using the voltage and the hours, then price it.

Watts from volts and amps — for battery, automotive 12 V, and solar-string systems where voltage is known.

Back out an unknown supply voltage from a measured load — the third leg of the W = V × A triangle.

Runtime from capacity, load, and usable depth of discharge — lead-acid 50%, lithium 80%.

Amp-hours × volts to watt-hours — the only fair way to compare batteries of different voltages.

The right generator wattage — running watts plus one starting surge, with 20% headroom.

What it costs to charge — battery size, the 20–80% window, your rate, and charging losses.

What electric heating costs to run — and why every 1,500 W resistance heater costs the same.

Size an off-grid or backup battery bank — usage, days of autonomy, voltage, and usable depth.

Turn watts and hours into kilowatt-hours — the building block behind every cost calc.

Dollars saved by replacing a device with an efficient one — annual, monthly, and kWh.

What a whole-house switch to LED bulbs saves — by bulb count, wattage, and hours.

Power factor and reactive power from real watts and apparent VA — the power triangle.

Voltage lost over a wire run — current, distance, gauge, with the 3%/5% verdict.

How much energy a device uses — watts, hours, and days to kWh, no dollars.

Your true all-in electricity rate — divide a bill total by the kWh used.

What a heat pump saves vs resistance heat — the COP cuts the electricity to a fraction.

Estimate a gas bill from therms and your rate — with the true all-in cost per therm.

Which is cheaper to heat with — same useful heat, gas furnace vs heat pump or resistance.

What it costs to heat your hot water — gallons, temperature rise, and resistance vs heat pump.

What standby (vampire) power costs a year — devices, watts idle, and your rate.

Convert kilowatt-hours to BTU — bridge the electric and heating/cooling worlds.

Convert BTU per hour to watts — a power conversion, not the kWh one it gets confused with.

Convert BTU to kilowatt-hours — turn a heat-energy figure into the energy your meter counts.

Convert watts to BTU per hour — why a 1,500 W heater is also a 5,118 BTU/h heater.

A commercial bill — a per-kW demand charge on your peak plus per-kWh energy, with the demand share.