Pem’s Tech Blog

Energy cost for a house/apartment is typically done in KWH, aka kilowatts hours, aka kilowatts * hours.  For example, if we have a 60 watt light bulb on for 1 hour, then that’s 60 KWH; which at 11.5 cents per KWH is $0.0069 per hr.  Or, if we have five 60 watt light bulbs on for 24 hours, then that would be 5 bulbs * 60 watts/bulb * 24 hours * 1/1000 watts/kilowatt = 7.2 KWH, which at 12 cents per KWH would cost 7.2 * $0.12 = $0.864 = 86.4 cents per day, which times 30 days/mo would be $25.92 for the month.  If the light bulbs were only on 8 hours/day, then it would be $25.92 * 8/24 = $8.64/mo, for those 5 light bulbs.

Here’s a real example of an apartment electric utility bill for 1460 KWH used in one month:
6.00 : Customer Charge
17.75 : Energy Charge at $0.0355  per KWH, for the first 500 KWH
75.07 : Energy Charge at $0.0782  per KWH, for everything over 500 KWH, in my case this was 960 KWH
53.33 : Fuel Charge   at $0.03653 per KWH, for 1460 KWH
1.52 : sales tax
Total Charges: $153.67, plus additional fees for solid waste, drainage, and street service (for driving a car), made the total $169.60

Notice that usage is bracketed (similar to federal income tax brackets).  In a house/apartment that used 1460 KWH last month, it’s reasonably safe to assume that a small change in KWH usage is not going to put us below the base 500 KWH.

So the important number here is:
(everything over 500 KWH) + (fuel charge) = (cost per KWH)

For my example, this is:
$0.0782 per KWH + $0.03653 per KWH = $0.11473 per KWH

However, let’s also account for the tiny $1.52 sales tax:
153.67 / (153.67 – 1.52) = 1.00999

So the sales tax must be 1%, or around 1%, which means:
$0.11473 per KWH * 1.01 = $0.1158773 per KWH

Pem (Admin) :: Oct.29.2009 :: Electricity :: No Comments »

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