The practical energy ledger
Read the numbers around your home
A useful energy plan begins with the things you can measure: power, time and the price of a unit.
Start with ordinary routines, identify where heat escapes, and compare changes using the same assumptions. Small
calculations become more valuable when they are tied to a real appliance and a repeatable habit.
Put an idea into practice →
Separate power from energy
Watts describe the rate at which an appliance uses electrical energy. Kilowatt-hours describe an amount used over
time. A one-hundred-watt load running steadily for ten hours uses one kilowatt-hour. The calculator combines power,
daily running time and days before applying your price per unit. Its currency is whatever currency your tariff uses.
Keep standing charges and other fixed bill items separate: turning a lamp off changes its energy use, but it does
not remove a daily charge that applies regardless of consumption.
Measure the routine that matters
A label's power rating is not always an appliance's average demand. Refrigerators cycle, washing
machines change through a programme, and computers vary with the work they are doing. Where appropriate, use a
suitable energy monitor according to its instructions and measure a representative period. Record the activity as
well as the number: a washing cycle at one setting should not be compared casually with a different programme. For a
lamp that draws steadily, the simpler calculation may be enough. Choose the effort of measurement to match the
decision you are making.
Keep warmth where it is useful
Walk around the home and note draughts at movable joints such as doors and windows. Address simple gaps with
suitable products while preserving intentional ventilation and any openings required by appliances. Curtains and
room use can change how comfortable a space feels, so record practical habits alongside equipment changes. Heating
schedules are most useful when they reflect occupancy and the way the building warms up. Adjust one setting at a
time and give the household a chance to notice the result before deciding whether the new routine works.
Compare a lighting change fairly
When replacing a lamp, compare useful brightness rather than choosing by watts alone. Light output, colour
appearance, fitting type and compatibility with existing controls all affect whether the replacement suits the room.
Use the calculator for both the old and proposed lamp with the same hours and tariff, then compare the estimated
energy costs. Purchase cost belongs in a separate comparison. If a room is used only briefly, its saving may differ
greatly from a reading light that stays on through every evening; actual use gives the numbers their meaning.