So, is it more efficient to put hot water in your cookiing pan when you are going to boil water, or to just run cold water out of the tap?

a guess: I suppose it depends on the efficiency of your hot water heater. If you had an 'instant on/hot' type system it might be beneficial to start with warmer water. Otherwise, I think you would use more fuel as you are warming an entire water heater full of water (again) and using more water waiting for that water to get to you.

Considering how the water supply is already messed up in places like here in Southern California...you want to conserve as much as you can.

Most water heaters will keep the water hot any way so you might as well use that.

My 4WD
Wife's 4WD

That depends on what efficiency your looking for. If you want boiling
water more quickly then use hot water tp start and you'll get boiling water faster than cold tap water to boiling. If you want boiling water the least expensively then it gets stickier. I have gas water heating and an electric stove. I suppose you would have to calculate the cost of attaining a BTU each way and extrapolate from there to get a true answer. That is not worth the effort to me - I'll just take reaching the boiling point the fastest (hybrid) way.

Alden Bowles
2005 Toyota Prius II HSD

In my case another factor comes into play... wasting water. In my building, our kitchen sink is about the farthest from the water heater as possible, and getting hot water at the tap (especially on a winter morning when the pipes and the water inside are thoroughly chilled) can take a long time and waste a lot of water.

What bugs me is when people fill the entire kettle to make a single cup of tea. Why waste so much energy to heat all that extra water?

Have you guys ever heard that you are not supposed to DRINK ( eat... cook... ) with the water from a hot water heater?

That water being hot in there ( the tank kind ) for hours and hours ( maybe days ) dissolves the metal, and then you drink the dissoved metal and it's not healthy.

So that alone may help you decide what to do.

Speaking of hot water....thought I'd toss in that hot showers can cause cancer.

Check out this chart of Radon levels before/after a hot shower:


Source:
http://www.physics.umaine.edu/radiation/radon.htm

Just can't win for loosing....if not one thing it's another.
I'll take my chances in this case.

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT

That was my first thought when I read the original post! I never use hot water for anything but washing dishes and such. In fact, it's recommended that you run your water until it's as cold as it can get before using it for cooking or drinking. That way any contaminants from the hot water heater (or the pipes if applicable) will have run through.

Here is a reference to metals in drinking water with a mention of hot water heaters:

http://tinyurl.com/byljj

Don't drink the hot water!

This has been informative!

All I knew was hot showers are not great for young-looking skin.

61.5mpg lifetime - 82mpg in recent months

Best Run >
www.cleanmpg.com

"fanatic" is what the lazy call the dedicated

the radon chart was for accumulation of radon in a closed shower in a closed bathroom (door closed, no vent fan running) and radon was probably coming from well-water.
if you leave the bathroom door open a few inches or run the exhaust fan, there's probably very little radon buildup.

and it depends on whether it's well-water or not. i live in Raleigh, NC and the tap water comes from a nearby lake. little chance of radon from that at all. any radon in my house seeps in from the ground, and running that same shower room fan helps get rid of it.

afraid to drink water from a hot water heater? check as to whether it's "glass-lined." if there's a fibreglas lining, there isn't much metal in contact with the hot water, so there's not much that's going to get dissolved and offer you a hazard.

here in NC, electric is relatively cheap and natural gas is relatively expensive. so if you want to figure out whether you should use hot or cold water for your teapot, start with electric versus gas heater, electric versus gas stove, and hot versus cold water.

then drive yourself crazy doing the math for something which is probably going to have an effect on your life somewhere out in the third or fourth decimal place.

much better to make it a rule to always wear seatbelts, whether you're in the front seat OR the back. you DO wear them when you're in the back seat, too, don't you? do you know why

if the car has a collision, the front-seat passengers are stopped dead in their tracks by the airbags and shoulder belts.
if you're in the back seat and not restrained by a seat belt, YOU then go slamming into the back of the FRONT seat-backs at the same speed the car had been going. if a body hits the back of a front seat at 60 miles per hour or so, it squashes the front-seat passengers between the seatback and the seat belts. it kills them.

fyi.

+af
Northwest Raleigh, NC, USA
'04 Silver opt.BC/9; 24,000+ miles so far
http://www.plusaf.com/prius/prius.htm
http://www.plusaf.com/coast/coast1.htm
My Prius without the trailer:

My Prius with the trailer: