Nameplate wattage times hours of use: the one multiplication behind every electricity estimate.
SYNTHETIC_NOTE: Sample content — replace with the launch copy before ship.
Energy in kilowatt-hours is power times time: E (kWh) = P (watts) × t (hours) ÷ 1000. A 100-watt lamp burning 5 hours a night uses 100 × 5 ÷ 1000 = 0.5 kWh for that night — the arithmetic never changes, only the inputs do.
What this guide does not do is name a price: the rupiah figure waits for the official tariff table, and until it lands the calculator shows energy only. An answer without its source is a draft, and this book publishes no drafts as facts.