UNDERSTANDING YOUR ENERGY BILL Robert Greenwald, P.Eng., MBA Pi Prism Engineering i Ld Ltd.
LET S START WITH A QUESTION HOW MUCH WILL THE ELECTRICITY COST TO RUN A 150 HP MOTOR FULL TIME FOR A YEAR? $12,000 $23,000 $41,000
BASIC ELECTRICITY VOLTAGE This is what pushes electricity through a circuit Units are volts (V) CURRENT This is what is pushed through by the voltage Units are amps (A)
ELECTRICAL POWER WHEN VOLTAGE AND CURRENT WORK TOGETHER TO DO SOMETHING USEFUL SUCH AS TURN A MOTOR OR LIGHT A LAMP Units are watts (W) 1000 watts = 1 kilowatt (kw) 1 horsepower (hp) = 746 watts
HOW TO CALCULATE POWER Watts = Volts x Amps x Power Factor VA = Volts x Amps PF = kw / kva Power Factor (PF) indicates how well the current and voltage are working together Incandescent lamps 100% Large motors 80 90% Small motors 60 75%
POWER AND ENERGY Power = How fast (a.k.a. demand) d) Energy = How much (a.k.a. consumption) Energy = Power Time Units are kilowatt-hours (kwh)
HOW FAST? HOW BIG X HOW MANY HOW MUCH? HOW FAST X HOW LONG Demand Power (Peak) Consumption Energy Kilowatts kw kva Kilovoltamps = Power Factor WHEN? Kilowatt X hours kwh
ANOTHER QUESTION HOW MUCH DO YOU PAY FOR ELECTRICITY PER KWH?
UNDERSTAND THE RATE STRUCTURE U EXAMPLE - ELECTRICITY January 250 000 kwh $12,500 February 250 250 kwh $12,887 Energy Up 0.1% but cost Up 3%? $1.55/kWh
THE REST OF THE STORY +250 kwh @ $0.037/kWh +50 kw @ $7.56/kW 50-kW HEATER FOR 5 HOURS
(kw) ast Demand How Fa New Peak = $378 Fastest Peak Demand (kw) How Much (kwh) 50 kw 5 hours 250 kwh = $9.25 How Long & When (Hours)
DEMAND METERS
100% Utility Meter Response to Load Registered on Meter % of Full Load 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Minutes Load Connected/Disconnected Ideal Response x Observed Values
ELECTRICITY BILL COMPONENTS BASIC CHARGE This includes the direct costs of metering, portions of the distribution ib ti system, as well as billing and customer service administration ENERGY CHARGE That portion of the charge for electric services based upon the electric energy (kwh) consumed DEMAND CHARGE That portion of the charge for electric service based upon the peak electric capacity (kw) required each month TAXES
INTERPRETING ELECTRIC METER DEMAND READINGS Demand meter register records in watts To get kw multiply the meter reading by: CT and PT external multipliers / 1000 Sometimes internal multipliers between 2 & 40 Marked on face of thermal or self contained meter and meter tag of a thermal Overall external multiplier often on a tag
INTERPRETING ELECTRIC METER DEMAND READINGS Energy meter register records in: kilowatt-hours (kwh) To determine the kwh consumed during a period of time: Present reading previous reading = difference Difference x external multiplier = energy consumed in kwh
Note: Rate not current
SAMPLE ELECTRICITY BILL WITH DISCOUNTS Note: Rate not current
WHY DO I CARE ABOUT PF? BC Hydro charges a penalty to distribution customers if PF<90% Increased line currents Low PF may suggest lightly loaded motors A useful tool in demand profile analysis Note BC Hydro bills transmission customers for volts x amps (kva) which is always greater than kw
BC HYDRO POWER FACTOR SURCHARGES POWER FACTOR SURCHARGE 90% -100% 88% - 90% Nil 2% 85% - 88% 4% 80% - 85% 9% 75% - 80% 16% 70% - 75% 24% 65% - 70% 34% 60% - 65% 44% 55% - 60% 57% 50% - 55% 72% 50% 80%
SAVINGS OPPORTUNITIES Peak Power = How Big x How Many When? Energy = Power x Time How Fast? (efficiency) How Long? (Hours of operation)
DEMAND PROFILE (ONE WEEK SHOWN)
WATCH THE BASE LOAD 1500 Peak = 1350 kw Kilowatts (kw) 1000 500 2nd Shift 1st Shift 3rd Shift Baseload = 950 kw Friday Saturday Sunday Monday 0 Long-weekend shutdown Time of day
PROFILE TO OPPORTUNITY Manage the turn-down ratio Reduce base load &/or night load levels Monitor load factor Should follow activity Compare load factor to utilization factor Manage peak demand Investigate time, duration, reason Demand warning/alarm
PEAK DEMAND CONTROL Eliminate accidental peaks Shift activity off-peak Warn staff about peak demand Interlock equipment Load shedding system Use generator to clip the peak
COMMUNICATE THE COST TO OPERATE EQUIPMENT Run the numbers (need unit costs) Make the numbers visible Posters Labels
HOW MUCH POWER COST TO RUN A 150 HP MOTOR FULL TIME FOR A YEAR? $12,000 $23,000 $41,000
Power: 150 hp x 0.746 kw/hp x 80% loading / 90% efficiency i = 99.5 kw Time: 24 hours x 365 days = 8760 hours/year Energy: 99.5 kw x 8760 hours/year = 871,620 kwh/year Demand Charge: 99.5 kw x $7.56/kW x 12 months = $9,027/year Energy Charge :871,620 kwh x 0.037 / kwh = $32,250/ year Total Cost = $41,277/year not including taxes or discounts
WHAT IT COSTS TO OPERATE A MOTOR Schedule Hr/year Demand Energy Annual Costs (kw) (kwh) 6 hours x 5 days 1560 100 155,000 $15,000 12 hours x 7 4368 100 435,000 $25,000 days 24 hours x 7 days 8760 100 872,000 $41,000
COST / kwh VARIES A LOT! Schedule Demand Energy Annual Costs Average Cost (kw) (kwh) per kwh 6 hours x 5 days 100 155,000 $15,000 9.5 cents/kwh 12 hours x 7 days 100 435,000 $25,000 5.8 cents/kwh 24 hours x 7 days 100 872,000 $41,000 4.7 cents/kwh OFF PEAK PRICE?
PRESENTATION SUMMARY 1. Find out what rate you are on and get the details on the rate structure 2. Understand your rate, both marginal and average 3. Understand your costs: collect historical data on kw, kwh, PF, $ 4. Identify when you reach your peak demand, how long it lasts 5. Identify what you can do to reduce the peak demand 6. Identify what you can do to reduce operating hours 7. Use the right marginal rate for your energy saving calculations (and ensure that others do as well) 8. Build awareness by sharing information on what it costs to operate plant equipment
THANK YOU Robert Greenwald, PEng., MBA President Prism Engineering Limited 604-205-5500 robert@prismengineering.com www.prismengineering.com