LED swap

Saved energy is (old W − LED W) × hours / 1000. Money is that times the unit price. A 1000-hour year is a lamp that is on about three hours a day.

Old bulb

LED

Hours in the period

Price per kWh

Saved

47 zł

Energy saved

52 kWh

The lumen output has to match. A dim 4 W candle is not a 60 W replacement.

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An educational estimate. Not medical, tax or credit advice.

A year of a device that never quite switches off.

Kilowatt-hours and the bill for a device from watts and hours a day.

A year’s space-heat demand from floor area and a rough insulation class, then electricity at a chosen SCOP versus gas.

A first-pass air-con size from floor area and watts per square metre.

The same yearly heat in gas, pellet, coal, wood, oil, resistance heat and a heat pump.

Heat and electricity to raise daily litres by a temperature difference, then a running cost.