What the heck is a kWh?

My electric bill is at the bottom so you wont have to go back and forth.

A Watt (named after James Watt, steam engine pioneer) measures power. Think of a 100 Watt light bulb. Think of 10 100 watt light bulbs burning at the same time in my condo. Those 10 bulbs are together using 1000 watts and someplace, a machine must be producing 1000 watts of power to supply them. The light bulbs turn 1000 Watts of power into heat and light; 1000 Watts is called a kilowatt, or kW. If I leave the bulbs on for an hour, I use a kilowatt-hour, or kWh. A kWh is the commercial unit of energy. We pay for energy, usually 1 kWh costs some cents, 2 cents to 10 cents depending on where you are in the USA.

I takes roughly one kilowatt to run a residence, more for a large air-conditioned place and less for a small apartment. My bill tells me I used 17.0 kWh on a typical 24-hour day during the 31 days covered by the bill. My power needs were less than a kilowatt, 7/10 in fact. My residence is a 1500 square foot condominium apartment. During the same period last year, I used 19.8 kWh on a typical 24-hour day. I probably saved energy by installing more compact fluorescent bulbs. I use hardly any incandescent or halogen bulbs any more.

Next post: what are all those different charges? Here is the bill again:


Residential Service 31 Days
Basic Service Charge $6.00
Energy Charge Summer 169.68 kWh @$0.067550 $11.46
Energy Charge Winter 356.32 kWh @$0.058070 $20.69
Environmt Imprvment Rider 526 kWh @$0.002100 $1.10
Fuel Cost Charge 526.00kWh @$0.0207898 $10.94
Resource Adjustment $1.11
Subtotal $51.30
State Tax @6.50% $3.33
Total Amount $54.63

My Latest Electric Bill; what the heck is a kWh?

I got my latest electric bill from September 20 2007 to October 21 2007. It was $54.63 for 31 days. This bill is so complicated that I will take a few posts to explain it.

Here is the bill:

Residential Service 31 Days
Basic Service Charge $6.00
Energy Charge Summer 169.68 kWh @$0.067550 $11.46
Energy Charge Winter 356.32 kWh @$0.058070 $20.69
Environmt Imprvment Rider 526 kWh @$0.002100 $1.10
Fuel Cost Charge 526.00kWh @$0.0207898 $10.94
Resource Adjustment $1.11
Subtotal $51.30
State Tax @6.50% $3.33
Total Amount $54.63

The arithmetic is always correct but you can check a few things: I used about 170 kWh and was charged about 7 cents for each kWh.
I used another 356 kWh and was charged about 6 cents for each additional kWh. The sum of 169.68 and 356.32 is 526 kWh exactly. I was charged another 2/10 of a cent times that much for an "environmental improvement rider" which added a dollar to my bill. I was charged about 2 cents for each of the 526 kWh for a "Fuel Cost Charge" (which added about $11) and then $1.11 "Resource Adjustment."


This all added up to $51.30 and then 6.5% Minnesota sales tax was added. What is a kWh? Explanation in next blog entry.

Take a Taxi from University of Minnesota to South High

In the Twin Cities, taxis work like this. The driver drops the flag to start the meter. A charge of $2.50 immediately shows on the meter. Then, each additional mile costs $1.90. In fact, if you go a fraction of a mile, there is a charge (more research needed). For this problem we will use whole miles. Note added Friday November 9 2oo7: I did the research (looked at the side of a taxi). Every 1/5 of a mile, the meter increases by 38 cents.

My granddaughter is a Senior at South High but takes some courses at the University of Minnesota. Usually she takes the bus (Metro Transit). But sometimes, time is short and I want her to take a taxi in that case. The distance from University of Minnesota (Wilson Library) to South High is three miles.

How much should I give her to pay for a three-mile trip including a 20% tip?

Prius Gas Mileage; October 2007

The dashboard display on my Prius hybrid shows that I have gone 375 miles since my last fillup and that the average performance has been 46.1 miles per gallon.

How many gallons of gasoline do I expect to need if I fill up now?

Gasoline today is $2.799 per gallon. How much do I expect to pay?