How to decide purchasing electrical equipments

Energy and Cost efficient Electrical Equipment

Suppose you go to a store and want to buy a fan. Sales man comes up with two fans, one with more price and other with less price. How will you decide what to buy. Ok, I'll tell you how to do this. 

• Ask power rating of both fans suppose one fan have $2400 and power rating of 79kW and other have $2900 price and 77.5kW rating.

• Now you will Find cost of electricity you have to pay for both fans. For this estimate time you need to estimate how many hours hours you need to use fan in a year. Just make a approximation. Suppose you live in a area where summer duration is 7 months. Then you can calculate it by 24*30 hours.I made 1600 hours in a year. Also find cost of electricity, I assume it  $.08 /kWh (You can see it from you monthly bill). Now calculate how much each fan will cost  you for every year in terms of energy usage.

                   P1(79kW   )  = 79.0 × 1600h/yr ×  0.08 = $10112/yr
                   P2(77.5kW)  = 77.5 × 1600h/yr ×  0.08 = $9920/yr

         It means you are paying 10112-9920=$192/yr              more if you purchase a fan with high                              power consumption.

         Now its upto you to pay an extra $500 for one                time or pay $192 for each year.


>> Data given on fan's vendor website you can find this on
http://gfcfans.com/product/karachi-model/

•  As you know value of money for today and tomorrow is different. 'Suppose  you have $100   today  and you invest it in a good project, that could earn you $12 then it means you can it could be 112  for next year. So might want to invest extra money instead of spending it on fan.Mean $10 in hand  today might have $600 value tomorrow, so we need to find today value of our money (This will  tell us weather to hold money or spend it) Formula is

          I assume life time of fan 20 years and d=10% so my value for this factor is 8.51/yr

• Now I'll add all the values and we'll decide what to choose..

                P(79kW)=$2400+8.5 *10112=88489
                P(77.5kW)=$2700+8.5*9920=87354

             So you will surely buy second motor as it saves your money....

             Same way you can calculate for AC and other electricity    equipment.

Some useful link

1. http://www.delmarfans.com/educate/ceiling-fan-rating-guide/
2. http://www.greenbuildingadvisor.com/blogs/dept/building-science/how-buy-energy-efficient-ceiling-fan