Archive for category utilities

The Navy Shower – Does it Pay?

Some Background


photo: _Teb

I see this idea batted around constantly. That we spend utterly too much time bathing ourselves, and sending all that water and heat right down the drain. We should be reclaiming the water, reclaiming the heat, and that by bathing, we are strangling mother earth and smiling (and smelling squeaky clean) as we do it.

One of the reasons I decided to do the math on this one is that someone on a forum called me out for shaving in the shower. I thought that he was just being finicky, so I decided to do the math, and let the chips fall where they may.

It seems that there are a great many variations on this topic, and I decided to crunch some numbers and see where the truth really lies. I am going to look at two different takes on daily bathing: mine, and that of the ‘navy shower.’ My guess is that your bathing method lies in the middle somewhere.

According to Wikipedia, a Navy Shower goes like this:

  1. Turn on the water
  2. Immediately wet the body
  3. Turn off the water
  4. Soap up and scrub
  5. Turn the water back on and rinse off the soap
  6. Turn off the water

That same article states that a navy shower uses about 3 gallons of water.

My shower is as follows:

  1. Turn on the shower
  2. Hop and and scrub up
  3. Warm up while listening to the radio
  4. Shave
  5. Rinse
  6. Hop out

Total water time: 15 minutes.

How to Make the Calculations

We are going to have to make a few approximations and assumptions here. I was going to throw a bucket under my shower head, and see how much came out in a minute, then use that number. I quickly realized that such a measurement was dependent on pressure and plumbing more than anything else.

I then read an article that stated that shower heads manufactured after 1992 were limited to 2.2 gallons per minute. This is at full pressure. I take my shower at less than full pressure. To make this number a little easier to deal with, let’s say that the average is 2 GPM.

So, this being the case, by shaving and listening to the radio in the shower, I use 30 gallons of water. About ten navy showers worth. This number is starting to hurt.

How they Bill you

The water department doesn’t bill you by the gallon. This number would be way too hard to measure, and would cause everyone to freak out as that number climbed sky high. The number that they bill you by is “Hundred Cubic Feet.” Imagine a cube 1 foot on each edge. Each hundred of those is what they bill you for.

You will have to look at your water bill to get the exact number. In my case, I had to back calculate. The interesting thing about my water bill is that I get billed for water coming in, and water going to the sewer. Both numbers are 12. What if I filled up a swimming pool? Would the sewer number be smaller? I really doubt it.


After all is said and done, I get charged $7.73 per hundred cubic feet of water.

The amount of water in a daily shower is tiny compared to a hundred cubic feet, so let’s make another assumption. Let’s assume that we bathe every day. A friend of mine says that is a sign that I am obsessive compulsive, but I will take that moniker in exchange for feeling clean and fresh in the morning.

That means that each month, I dump 900 gallons (!) down the drain bathing. That seems like alot. Let’s see how much it costs me.

Once cubic foot = 7.48 gallons

So each month, I use 1.2 hundred cubic feet (ouch) for a total of $9.28. This is a great deal more than I expected.

The same month in navy showers would cost less than a dollar.

Now, to heat that water!

There is really no way to accurately guess this number, but follow my logic here:

In the summer, my gas bill is about $30. I would guess that 1/4 of that is for cooking, which leaves $22.5 for heating water.

There are three people in my house showering daily. That means about 4 hundred cubic feet are used for bathing (they use more water than me).

That means 1/3 of the water (remember, I used 12 HCF per month) used was for bathing. That means 1/3 of $22.50 was used for heating shower water, or $7.50.

Taking that number again, and dividing by three to get my total, I used $2.50 to heat my water.

The Final Analysis

Each month, taking a fifteen minute shower each day, I spend $11.78. While this number is based on several assumptions and approximations, it is very close.

Taking a ‘navy shower’ each month costs $1.18 per month. An order of magnitude (and a real number!) cheaper.

Now, multiply this over the number of people in your house, and you can see that these are actually real numbers, and add up to some serious cash very quickly. I am now left to think really hard about this. I really like taking my warm shower in the morning. I don’t think i could go navy on this one, but if i only stayed in for 7 1/2 minutes, I could save almost six bucks.

If I were to shave in the sink after the shower, I could easily shave 5 minutes off my daily shower time. Think about it this way:

According to my calculations, I spend about 79 cents for each average minute in the shower. If I shave in the sink, I will save $4 a month. $48 bucks a year!

If I could get my family do do the same thing, we would have enough money left over to: go out to the movies an extra time a month, go out to dinner an extra time per month. Then again, it could rain hundred dollar bills for 40 days and 40 nights, and we’d all be rich.

Just sayin’..

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Turn out (or replace?) that light!


Does it pay?

When I was a kid, my parents would follow us around the house shutting off lights and mumbling something about money growing on trees. Now that I am a parent, I find myself in that same role. While I have no aspirations of finding that tree money grows on, I have started to wonder if:

  1. My panic at seeing all the lights on is warranted.
  2. Keeping all these lights running is really costing me that much money.
  3. Since I have replaced my burned out lights with CFL (compact fluorescents), is this taking the edge off?

I started crunching the numbers, and this is what i found.

Determining usage

In thinking about leaving lights running, I started thinking about several other things that run in my house. Servers, refrigerators, wall wart charges, and the like. Unfortunately, in order to test those devices, I need another piece of gear. For those technically oriented, I thought about rigging my meter so that I can put it in series with any of my gadgets, but I found that my meter does not read true RMS.
It turns out that the Kill A Watt EZ Electricity Usage Monitor does just this, but without the dangerous wiring. It’s on my wishlist , so if anyone decides to buy it for me, I promise to test everything in my house, and post the results for all to see.
The gist is, you plug your item into this gizmo, and it calculates how much power is used. This can easily be converted to dollars.

How the electric company figures your bill

The electric company pretty much has a gizmo just like this (but more rugged, and more thoroughly calibrated.) Your bill is based on killowatt hours. This is wattage used by an appliance multiplied by the time that wattage is used. For example:

  • A 100 watt bulb, running for ten hours, uses 100 watts x 10 hours / 1000w/kw = 1 killowatt-hour.
  • If you look at your electric bill, you will see that they tell you how much you pay per killowatt-hour. First Energy charges me 7.36 cents. So the cost to me to run that 100 watt bulb is 7.36 cents.

Okay, so that number doesn’t seem to warrant too much freaking out.

Checking out my house

I did a quick check on my house, to see what lights get left on most often. Those are: The living room, the kitchen, basement. Just to be fair, I gave decided to estimate the hours that the lights were on when no one was using them. That time was about two hours per day.
This is how it worked out:

RoomTotal WattageCost Per Month
Living Room100W + 100W + 60W = 260W260W * 2hours * 30days * .0736 = $1.15
Kitchen60W total60W * 2hours * 30days * .0736 = 26 cents
Basement (all CFL)42w + 42w + 20w = 104w104w * 2hours * 30days * .0736 = 46 cents

So, this tells me that if I fret and run around the house turning off lights, I stand to save less than two bucks. If I relax about the lights, I get to settle down a bit, and it only costs me two bucks.

Replacing my lights with CFLs

Compact Flourescent Lights are dropping in price every day. Now, whenever a bulb burns out, I replace it with a CFL. I decided to do a little calculating to see how much this transition saved me over the course of a month.

My house is small. We only have about three rooms being lit at once, and then, only for an average of about 5 hours per day. That number will rise in the winter, but not much. So, let’s see how much it costs me to light my house, assuming those numbers, as opposed to incandescent lighting.

The trick with CFLs is they give you two wattage ratings. One, the wattage rating for the power they use, and the other, the equivalent incandescent wattage. In each room, we have two 26 watt bulbs (100 incandescent watts each) and one 15 watt (60 incandescent watts) bulb. This gives me 260 incandescent watts for the cost of 67 watts.

So, here’s how much it costs to light my house either way, assuming 3 rooms, 260 incandescent watts, 5 hours/day, and 30 days:

LightingKillowat-hours / monthCost/Month
Incandescent3 * 260W * 5hours * 30days = 117kwH$8.61
CFL3 * 67w * 5hours * 30 days = 30.15kwH2.21

So, the total savings for each month is $6.41.

Now, if you are in a similar situation, but have not made the transition to CFL yet, you can assume the lights will cost you about $3.20 each. In this case, each month, the cost of two bulbs will be saved. So, in my case, I recouped the cost of the bulbs in five months.

Is it worth it?

From what I understand, all bulbs will be switching to CFL soon, so we will not have a choice. But yes, it seems to be worth it. In order to get an equivalent light, you spend about a quarter of the cost in electricity.

As for shutting off every light in the house as and following people around to do so, no, it’s not worth it. Now that the usage has dropped by three fourths, it is really not worth it.

Now, my electric bill is still about $100 dollars a month. This might justify me buying the Kill A Watt EZ Electricity Usage Monitor to track down the culprit, but at this point, it’s not a good idea for me to be spending money. I have a suspicion it’s the cable box, the tivo, the tv, or some major appliance.
So, remember that wish list , and if I get one, I promise to teach you all how to find what is killing your electric bill.

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