How we calculate the saving
We compare the monthly consumption of all LED bulbs with the previous lamps using the same hours and electricity price.
bulbs Γ W Γ· 1000 Γ hours Γ days Γ β¬/kWh
Compare lumens, not just watts
Watts measure power use; lumens measure light output. A fair comparison needs similar brightness.
Savings depend on operating hours
A rarely used hallway saves less money than lighting that runs for many hours every day.