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Quick Start for:

Calculating Energy Costs
Example: BEVERAGE MACHINE ENERGY COST


Machine Characteristics
16-17 amps on start-up
7 amps when running
lamps plus ballasts


Other
Typically on dedicated 20 amp circuit
Electric Cost = 9.5¢/kw-hr


Calculation
P =   VI  
      1,000


Refrigeration
P = (120V) (7 amps) = 0.84 kW
              1000

Assume 30% run time

kW-HR/Mo. = (0.84 kW) (0.3) (24 hr/day) (31 days/mo.) = 187.48 kW-hr/mo.


Lamps and Ballasts
For two 40-watt lamps and 22-watt ballasts = 102 watts/machine

(0.102 kW) (24 hr/day) (31 days/mo.) = 75.88 kW-hr/mo.


Heat Rejected To School Space That School’s A/C Must Operate To Remove
187.48 kW-hr/mo. + 75.88 kW-hr/mo. = 263.36 kW-hr/mo.

263.36 kW-hr/mo. x 3413 BTU/kW-hr = 898,847 BTU/mo.

(898,847 BTU/mo.) (mo./744 hr) = 1208 BTU/hr

(1208 BTU/hr) ( 1 ton-hr/12,000 BTU) = 0.1 ton cooling extra

(0.1 ton) (1.2 kW/ton a/c eff.) (0.3 run time) (24 hr/day) (31 days/mo.) = 26.78 kW-hr/mo.

Lamps and ballasts - 75.88 kW-hr/mo.
Refrigeration - 187.48 kW-hr/mo.
Additional A/C - 26.78 kW-hr/mo.

TOTAL - 290.14 kW-hr/mo.

Cost/Month = $/Mo. = $27.56/mo. or $330.76/yr per machine


If lamps and ballasts disconnected, savings will be:

Lamps & Ballasts

(75.88 kW-hr/mo.) (12 mo./yr) ($0.095/kw-hr) = $86.50

Heat Rejection of Lamps and Ballasts

(75.88 kW-hr/mo.) (3413 BTU/kW-hr) (mo./744 hr) = 348.09 BTU/hr

(348.09 BTU/hr) (1 ton-hr/12,000 BTU) = 0.03 ton cooling extra

(0.03 tons) (1.2 kW/ton) (0.3 run time) (24 hr/day) (31 days/mo.) = 8.03 kW-hr/mo.

(8.03 kW-hr/mo.) (12mo./yr) ($0.095) = $9.15

Removing lamps and ballasts saves $86.50 + $9.15 or $95.65/yr per machine