Excessive Conservation Wearing Out [noun]... Answered
So... While brushing my teeth - I first rinse my brush, turn the faucet on, brush, then rinse the sink/mouth. Yes, I turn the faucet off while brushing. And if you're counting - that's two on/off cycles per brushing...
I've been playing with this tool: http://www1.eere.energy.gov/femp/procurement/eep_faucets_showerheads_calc.html
And I pose an open question for discussion.. But first, my data/research...
I'm estimating 3 minutes of use per day - 365 days/year. According to the tool... I use 2190 gallons per year. Lets say that's 5 uses per day (2 for teeth - 1 for bathroom use). The tool seems to estimate an 8.4 year service life - so that's a total of 18396 gallons of water over it's life as a faucet.
So If I leave the water on while brushing - that's 3 on/off cycles per day.
If I turn the water off while brushing - That's 5 on/off cycles per day (40% more cycles).
Realistically, a faucet's wear comes from on/off cycles - each use bringing it closer to retirement. So 40% of 8.4 years is 3.4 years.
Now... Leaving the faucet on an extra 4 minutes per day (2 minutes per brushing) consumes 2920 gallons of water per year.
The difference over 8.4 years is: 30660-18396=12264 gallons. At about $4 per 1000 gallons - that difference is $49.06. BUT, the direct replacement for my faucet (as priced today in home depot to the exact model) is $75. So after 8.4 years
Faucet remaining on will cost me:
$49.06 + $75 = $124.06
Faucet being turned off will cost me:
$75 + $30(prorated cost of faucet for 3.4 years of wear on a new faucet) = $105
12,264 gallons of water
That is to say - due to extra wear on my faucet - it's only marginally more economical to turn my faucet off while brushing my teeth. If I wasn't me, and not able to DIY replace - it very well may be cost effective to leave it on given the cost of a hiring a handy man or plumber...
Okay... Now that you've read the above... please discuss your thoughts. I am very much aware of the assumptions I have made (no need to point them out) - just looking for opinions :)
UpdateLets turn this discussion on it's head now... As several have pointed out, conserving is more important - bonus as it's close to an economical wash in my fictitious scenario above (it's not 100% real and based on data from the link above and some hefty assumptions).
My car uses .3 gallons of gasoline per hour at idle. Lets take a 100% city drive in heavy traffic (my drive yesterday). I was at a complete stop due to traffic lights or traffic for 20 seconds or more a total of 12 times to travel ~10 miles (yes, I freakin timed it). So that's a total of 4 minutes (wow, that worked out nice) of idle time. That time consumes 0.02 gallons of fuel costing me $0.06. If I were to make that commute 5 days a week, twice daily - that's a cost of:
10.4 gallons of gasoline
$31.2 worth of fuel
So, a new starter for my car costs $130. Typically the motors don't actually die - just the contacts. But lets assume I don't want to fiddle with that and just want to direct replace (corollary to valve washers :D).
This means - using my starter an additional 24 times per day - it will take 4.2 years for the fuel savings to pay for a new starter. In 4.2 years - averaging 12,000 miles per year - I will have traveled 50400 miles.
Okay - now lets consider the cost of fuel to restart - 24 times.... According to mechanical engineering magazine, a V6 engine used 5 seconds worth of idling gasoline to restart. So - redoing some math to compensate - that's a savings of
7.8 gallons of gasoline per year
$23.4 per year
Time to recoup 1 starter: 5.6 years (equating to 66000 miles)
So, I'm having some problems finding data on starter life cycle - all I have is anecdotal evidence...
*My personal car has 115K miles and is ~8 years old - and I've been doing this since I bought the car >2 years ago.
*My last car was sold at 98K miles and this was done for a little less than 2 years (the car was 8/9 years old when sold).
*My first car had unknown mileage (estimated around 150K), was 10 years old and the engine was killed at stoplights.
*My parents own a conversion van (seldom used now) that is 12 years old, 120K miles - did not shut the engine (v8) down at traffic lights.
None of the cars above have had their starter go.
*Father had a truck that had it's starter replaced around 220K miles - unknown age. That car left us with a blown connecting rod around 300K miles
Batteries... Yes, this does put more strain on your battery... I'll go more into that when I can find some better data (more than anecdotal :p)...
But, that's to say... It's economically viable to turn off your engine at traffic lights... So much so, it's illegal to idle (over a certain period of time) at traffic lights in some countries...