Watts to kWh: calculate appliance electricity cost
Convert power and running time into energy, then estimate cost using actual tariffs and realistic operating hours.
Energy
Energy: Practical explanations, worked examples and calculators for everyday decisions.
Standby power cost: watts to annual kWh
Estimate the yearly electricity cost of an always-on device, and learn when a nameplate wattage is the wrong input.
Solar panel payback: calculate from your electricity bill
Estimate simple payback using installed cost, usable production, self-consumption and the tariff actually avoided.
Appliance duty cycle: estimate electricity cost when a device cycles on and off
Calculate energy use from watts, runtime and the fraction of time a compressor, heater or motor actually draws full power.
kW versus kWh: calculate energy from appliance power and time
Understand why a kilowatt measures instantaneous power and a kilowatt-hour measures consumed energy on a bill.
Battery backup runtime: estimate hours from Wh and device watts
Estimate how long a power bank or backup battery can run a device after usable capacity and conversion losses.
Series and parallel resistors: total resistance and current
Calculate equivalent resistance for simple circuits and check power before choosing parts.
Heat conduction: how thickness and area change the rate
Estimate steady heat flow through a flat layer while distinguishing watts, energy and material conductivity.
Carnot efficiency: use absolute temperatures, not Celsius ratios
Calculate an ideal heat-engine limit and compare it with efficiency from measured heat and work.