An office in Reading is almost exclusively lit by T8 4ft tubes, with160 light fittings in total. The distribution of light is inadequate and the running costs are high.
A model is produced to model an improved light distribution, with a target maintained light level (achievable after 10 years of degradation) on the horizontal desk surfaces of 500 lux.
The lights are replaced by 260 40W 600m x 600m LED Panels at a cost of £16,040 + VAT.
The running load is reduced from 28kW to 10.4kW, resulting in a 63% reduction in running costs, and annual savings of £5,530.
The investment payback time is just under 3 years.
|Existing lights||Proposed LEDs|
|Max load (kW)||28||10.4|
|Total no of fittings||160||260|
|Average running hours per annum||2890||2850|
|kWh consumption per annum||80,920||29,640|
|kWh reduction per annum||51,280|
|As a % of current usage||63%|
|Running cost reduction @ 10.5p per kWh||£5384|
|Maintenance cost reduction per annum||£146|
|Total savings per annum||£5,530|
|Cost of upgrade (ex VAT)||£16,040|
|Payback time||2.9 years|
|Reduction in carbon footprint|
|CO2 reduction per annum||27.6 tonnes|
For this project, four year lease financing is available at a cost of 8.0%, with payments of £4840 per annum. These are more than covered by the savings made in running costs. The full cash flow is set out below.
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