#### Zondrina

Homework Helper

- 2,063

- 136

**Calculating yearly cost of running coffee makers**

**1. Homework Statement**

Find the total cost for operating two 15Ω coffee makers connected to a 120V power supply for two hours a day each for one year.

**2. Homework Equations**

##R = 15Ω##

##V = 120V##

##∆t=(2h)(365)= 730h## Two hours each 365 days a year.

##r_¢=6.4¢/kWh##

##I = V/R = 8A##

There is some basic physics involved, it's the answer I'm concerned with arithmetically.

**3. The Attempt at a Solution**

I find the power of one coffee maker using :

##P = IV = (8A)(120V) = 0.96kW##

There are two coffee makers, so the total power is :

##P_{Total} = (2)(0.96kW) = 1.92kW##

The energy would then be :

##E = P_{Total}∆t = (1.92 kW)(730h) = 1401.6 kWh##

Therefore the total cost is :

##C = Er_¢ = (1401.6 kWh)(6.4¢/kWh) = 8970.24¢ = $89.70##

Is this correct? The answer is listed as $370.02 so I'm not so sure.

Last edited: