LED Bulb Payback: A Room-by-Room Savings Worksheet

Start with the lights that combine a large wattage reduction, long operating hours, and a modest replacement cost. A kitchen light used every evening has a different payback from a rarely used closet bulb. Replacing a working LED with a slightly lower-wattage LED deserves its own calculation—not an assumption that newer means worthwhile savings.

Use actual input wattage, not the replacement’s “watt-equivalent” description. The FTC’s bulb-shopping guide explains that lumens describe brightness and watts describe electricity use: a traditional 60-watt incandescent produces about 800 lumens, while an LED can provide that output using about 9 watts.

Build one worksheet row for each usage pattern

Group bulbs only when their wattages and operating hours match. Two lights in the same room may need separate rows if one stays on throughout the evening and the other is used briefly.

For each row, record:

• Room or lighting task and bulb count
• Existing wattage and proposed replacement wattage
• Existing or desired lumens
• Average daily operating hours
• Electricity rate per kWh
• Complete replacement cost, including any associated control or fixture work

For seasonal lighting, use annual operating hours instead of assuming the same daily use all year.

Calculate electricity savings and simple payback

annual kWh saved = count × (old watts − new watts) × hours/day × 365 ÷ 1,000
annual dollars saved = annual kWh saved × avoidable electricity rate
payback in months = complete replacement cost ÷ annual dollars saved × 12

These examples use hypothetical inputs, including a $0.18/kWh electricity rate and assumed project costs. They are not measured household results, product specifications, or shopping prices. The working-LED comparison assumes the two options provide comparable useful light.

| Example use | Count | Old → new watts | Hours/day | Annual kWh saved | Annual dollar saving | Assumed total cost | Simple payback | |---|---:|---:|---:|---:|---:|---:|---:|---:| | Kitchen lamps | 4 | 60 → 9 | 4 | 297.84 | $53.61 | $20 | 4.5 months | | Closet lamp | 1 | 60 → 9 | 0.25 | 4.65 | $0.84 | $5 | About 6 years | | Working LED replacement | 1 | 9 → 7 | 4 | 2.92 | $0.53 | $5 | About 9.5 years |

The kitchen and closet examples have the same per-bulb wattage reduction and assumed per-bulb cost. Their different paybacks come from operating hours. The working-LED example runs as long as the kitchen lights, but its wattage reduction is much smaller.

Use these accounting rules to make the comparison meaningful:

• Count only charges the project can avoid. Include applicable per-kWh charges, not a fixed monthly utility fee that remains unchanged. For time-of-use billing, calculate savings separately for each rate period.
• Include the whole project’s cost. Add any necessary dimmer, fixture, labor, or disposal costs rather than using the bulb price alone.
• Choose the right baseline. For an early replacement of a working bulb, compare the purchase against continued use. If a bulb has already failed, compare the additional cost and electricity use of two suitable replacement options; continuing to use the failed bulb is not an alternative.
• Treat the result as simple payback. It excludes future rate changes, financing, later replacements, and heating or cooling effects. If annual energy savings are zero or negative, there is no energy-only payback.

Match useful light before comparing watts

The FTC’s Lighting Facts guidance identifies brightness, wattage, estimated yearly energy cost, expected life, and warm-to-cool appearance as package comparison points. Use lumens to establish the brightness you want, then use actual watts in your worksheet. The package’s yearly cost is not a substitute for your own hours and electricity rate.

For recessed or task lighting, consider distribution as well as total output. DOE explains that fixture design and optical control affect how much light reaches the intended area. ENERGY STAR’s downlight criteria likewise address light distribution separately from total lumens. Compare the intended illuminated area—not just the biggest lumen number—when choosing light for a counter or reading task. (DOE: LED Basics; ENERGY STAR: Downlight Criteria)

Choose color temperature for appearance, not savings. ENERGY STAR describes 2700–3000K as warmer-looking white light and 4000K or higher as cooler-looking. A warm option is a starting point for someone who prefers a yellower evening light; someone who prefers a cooler appearance can compare higher Kelvin values. Try the preferred appearance in the room before committing to a whole group. (ENERGY STAR)

Use color rendering as a separate comparison. DOE generally recommends CRI of at least 80 for interior lighting and describes 90 or above as excellent color fidelity, while noting that CRI has limitations. Higher fidelity can involve cost and efficiency tradeoffs. For a light used to view food, fabrics, or artwork, that tradeoff may matter more than a small wattage difference. (DOE)

Include dimming requirements and realistic life expectations

For dimmable downlights, ENERGY STAR requires information about compatible controls, known incompatibilities or limitations, and the dimming range. Compare those details with the exact control you plan to use rather than treating “dimmable” as a complete compatibility statement. A minimum light level that suits a kitchen may not suit a bedroom used at low light. Include any required control replacement in the project cost. These are downlight-specific criteria, not proof that every household LED bulb meets them. (ENERGY STAR)

For recessed downlights, insulation-contact approval is also separate from lighting technology. ENERGY STAR requires products marketed as Type IC to have laboratory approval for zero-clearance insulation cover. An “LED” label alone does not establish that approval. (ENERGY STAR)

Rated life is not a promise that every component will operate unchanged until that point. DOE describes LED useful life in terms of light output declining to 70% of its initial level; it also explains that electronics failure or unacceptable color shift can end useful service. A long payback therefore deserves more caution than a short one: the worksheet does not establish whether the replacement will remain useful long enough to recover its cost. (DOE)

Calculate controls as a separate upgrade

DOE describes dimming, color control, occupancy sensing, daylight-responsive control, and local light-level control as LED-system capabilities. That does not mean every LED bulb includes those features. Choose a control to address a specific use pattern, such as lights left on in an unoccupied room, rather than assigning automatic savings to a “smart” description. (DOE)

For a control that reduces operating hours without changing the light’s on-state wattage:

additional annual kWh saved = count × LED watts × annual hours eliminated ÷ 1,000

Use the new LED wattage, not the old incandescent wattage, when evaluating controls added after a bulb upgrade. Otherwise, the same savings can be counted twice. Subtract any additional standby consumption and compare the remaining dollar savings with the control’s complete installed cost. ENERGY STAR’s downlight criteria allow standby consumption for certain sensor-equipped and connected designs; they do not establish the consumption of a particular bulb or control. (ENERGY STAR)

The worksheet needs bulb count, wattage, operating hours, electricity rate, and project cost—not panel-monitor data. It estimates lighting electricity from those inputs; it does not measure household consumption. Revisit your estimated hours after observing normal use, then prioritize the rows with the strongest savings and acceptable light quality.

Sources

• FTC: Shopping for Light Bulbs
• ENERGY STAR: Downlights Key Product Criteria
• U.S. Department of Energy: LED Basics