Enter your bulb's Luminous Flux (Lumens) and select a Bulb Type (or plug in a Custom Luminous Efficacy) to calculate the bulb's Power Consumption in Watts, along with the Luminous Efficacy used and an Estimated Annual Energy Cost based on 3 hours of daily use at $0.12/kWh.
Power Consumption
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Luminous Efficacy Used
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Estimated Annual Cost (3hrs/day @ $0.12/kWh)
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Lumens measure the brightness of light output, while watts measure electrical power consumption. A higher lumen count means brighter light, while higher watts mean more energy used.
Luminous efficacy (lm/W) measures how efficiently a bulb converts electrical power into visible light. LED bulbs typically achieve 80-100 lm/W, while incandescent bulbs only reach 12-18 lm/W.
Focus on lumens for brightness needs, not watts. For example, 800 lumens (equivalent to old 60W incandescent) requires only 8-10W with LED technology.
Use the formula: Watts = Lumens ÷ Luminous Efficacy (lm/W). For example, 800 lumens ÷ 90 lm/W = 8.9 watts for an LED bulb.
LED bulbs convert most electrical energy directly into light, while incandescent bulbs waste about 90% of energy as heat. This makes LEDs 5-6 times more efficient.
Living rooms need 1500-3000 lumens, bedrooms 1000-2000 lumens, kitchens 3000-4000 lumens, and bathrooms 2000-3000 lumens depending on room size.
LED bulbs use 75-80% less energy than incandescent bulbs. A 60W equivalent LED (9W actual) can save $50+ per year compared to incandescent when used 3 hours daily.