For this life-cycle cost model, it

For this life-cycle cost model, it is important to understand that the per-lamp LED cost is a system cost, so the cost of the linear LED lamp, driver, and any ballast needed for the system is included in the prices shown. As previously stated, the linear LED lamps (modelled at 38 W per luminaire) generally compared favorably—the green shaded areas in Figures 1 through 4—to the fluorescent retrofit option (modelled at 51 W per luminaire) when the cost of electricity was high ($0.18 or $0.24/kWh), when the hours of use were longer (4,000 hours/year), and when the linear LED system cost was $80 per two-lamp troffer or less. Simply stated, higher utility rates yield greater cost savings and reduce payback periods. A lower cost of $40 per two-lamp troffer made the linear LED lamps more economically viable at more moderate electric rates and lower annual hours of operation.