Nashua South High School
ECM 1 - LED Lighting
The schools currently utilize a combination of T8 and T5 fluorescent lighting. EEI proposes
replacing the existing fixtures with new LED lighting. EEI performed a detailed survey of the
interior and exterior spaces in order to identify opportunities in which we can improve
lighting quality, reduce maintenance costs, and save energy.
The existing lighting demand (kW) per fixture, hours of operation, fixture quantities, and
recommended retrofits are based on the physical inspection and site visits conducted by EEI
in 2019. As a result of the survey and analysis, EEI has developed a high efficiency lighting
upgrade project that will provide the schools listed with new LED fixtures with controls,
resulting in guaranteed annual energy savings and a reduction in electrical demand.
LED type lighting provides significant illumination, has longer life expectancy, increased
savings in electric consumption, and provides dimming capabilities. Also, standardizing all
fixtures will reduce future maintenance requirements.
LED fixtures in a school environment have an estimated life of more than 20 years. There is
significant maintenance savings when LED fixtures are used due to their longer lifespan.
All light energy eventually converts to heat. The conversion to LED fixtures will reduce the
building’s lighting energy intensity (kW/sq. ft), therefore impacting the HVAC heating and
cooling loads. Converting to LED lighting will eliminate 2,795 mmBTU waste heat annually.
The reduction in lighting waste heat will increase the HVAC load during heating season,
approximately 11,967 therms annually. Conversely, the HVAC load will decreasein the
cooling season, approximately 55,849 kWh annually. The net HVAC utility impact is an
increase in cost of approximately $3,589. This increase in cost has been subtracted fromthe
energy savings for the ECM. Please see below for the formulas used to calculate the net
savings affect.
HVAC Heating Load Increase = (Net Annual Interior LED Lighting kWh Savings * Btu
Conversion Factor * Therm Conversion Factor* % of Time HVAC Systemis Heating * Utility
Rate per Therm) / (Heating System Efficiency)
HVAC Cooling Load Decrease = Net Annual Interior LED Lighting kWh Savings * Btu
Conversion Factor * Cooling Tons Conversion Factor * % of Time HVAC Systemis Cooling *
Cooling System Efficiency * Utility Rate per kWh
Assumptions:
o Net Annual Interior LED Lighting kWh Savings = 819,850 kWh
% of time HVAC Systemis Heating = 3000 hours / 8760 hours = 35%
% of time HVAC Systemis Cooling = 3000 hours / 8760 hours = 35%
Heating System Efficiency = 80%
Cooling System Efficiency = .7 kW/ton
Utility Rate per Therm = $1.00/therm
Utility Rate per kWh = $.15/kWh
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