any idea what it costs to heat a gallon of water from say 50 degrees to 120 degrees at 10 cents per KWH?
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That would be 583 BTUs or 0.17 kWh, or 1.7 cents.
$.017
There are ~8.33 lbs. of water in a gallon and it takes ~1 BTU to heat one pound of water one degree fahrenheit. So, you will need ~583 BTU's.
There are 3,412 BTU's in a kWh- only ~17% of a kWh will be needed.
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
Water is 8.33 lb/gallon
From 50 to 120 is a 70 degree rise (F, not C).
BTU is heat to raise 1 lb of water by 1 degree F.
So, you've got 8.33 * 70 = 583 BTU.
One KWH is 3412 BTU, so that 583 BTU is 0.171 KWH.
At $0.10 per KWH, cost for that gallon is 1.71 cents.
Edit: jeez, I guess this was a typing speed contest!
Edited 12/31/2008 2:50 pm ET by DickRussell
It takes 8.34 BTU to increase one gallon of water one degree F. So that is 8.34 btu * 70 (# of degrees) = 583.8 btu.
1.0 kilowatt-hour (kWh) = 3.6 MJ = 3413 Btu.
583.8 / 3413 = 0.171051861 kwh
0.171051861 kwh * 10 (cents) = 1.71 cents to heat your gallon of water.
DUH, nobody got it right yet, closest would be heating a gallon surrounded by lots of insulation with an imersion heater.
Poor engineering, nobody added in the losses - microwave probably the most expensive, good water heater right at the tank probably closest to theoretical.
If electricity used via a de-superheater on AC, then the cost is much less than the 1.7 cents.
Edited 12/31/2008 3:14 pm ET by junkhound
Well, a modern electric tank water heater has essentially zero loss, if your time horizon is a few hours.What you're really pizzed at is that everyone got the same answer, so there's no argument. We need a good argument on this virtual Friday.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
The de-superheater is what???
The de-superheater is what
On a vapor compression cycle machine, the refrigerant (R22, R410A, etc) leaving the condensor is slightly warmer than the air it is heating.
So, if you are running your AC on a 90F day, the refrigerant leaving the condensor (outside coil as AC) is between 95F and 100F. You can run that tubing thru a cold water tempering tank to the water heater to cool it down, thus the liquid to and the vapor from the evaporator is cooler as some of the heat rejected fromthe house went into the colder water. Lots of different cycle variations possible.
Gotcha. And the cold water makes the AC coils more efficient at extracting heat, while increasing the efficiency of the water heating.
The de-superheater is what???
Also known as a desuperator.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Desuperheater is de ting dat keeps Superman warm.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Ok, I'll guess 5.87732 cents / gallon then.
All you guys are wasting your time here.
You should find some nuclear physicist site someplace.A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
LOL, you mean where the BTUs are free but the facility for heating the water costs 179million plus rod disposal fees?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Alright,
Try Nucular........A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
LOL, you mean where the BTUs are free but the facility for heating the water costs 179million plus rod disposal fees?
Not a laughing matter. The earliest commercial nukes in the US cost about $179 million. By the early 80s, they were costing $1.7 billion to build (10x as much) and by the late 80s $5 billion (nearly 30x as much).
And that doesn't include operation, waste storage, decommissioning ($2-4 billion), or insurance (which is largely federally-subsidized). American taxpayers have already given the nuclear industry a "bailout" in the form of subsidies of $97 billion since 1950.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
hey.... lighten up..... happy new year !Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Same to you.
well, the Happy New Year part.A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
and here it is 09 already.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Yeah ... lighten up you guys! Geee Wwwhizzzz.
First four that buzzed in were right on ... and fast!!! They got the basics down pat ... now what should we do? I'd go sailing, but it's the middle of winter.
It IS a laughing matter for a human being with a sense of humour.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
$97 billion spread out over 58 years sure seems like a much better deal than the $700 (or so) billion dished out this year....
I suspect that millions of people benefit in some way from nuclear power, and a few thousand or tens of thousands will pocket the $700 billion without any accountability.
I don't know which is the bigger evil... coal or nuclear... but the need for electricity is still there.
"...but the need for electricity is still there."yes, but....splitting atoms to heat domestic hot water 50*F....electricity is energy of high order - might ought to be reserved for tasks that require those energies...."there's enough for everyone"
$97 billion spread out over 58 years sure seems like a much better deal than the $700 (or so) billion dished out this year....
I agree, but that figure includes only the direct subsidies. I don't believe it includes the cost of the goverment-owned waste repository that they keep promising to build and maintain forever.
And it doesn't include the potential government payout for a Chernobyl-type accident. Because no private insurance company will cover a nuclear accident, the Price-Anderson Act was passed in 1957 to indemnify the nuclear industry for any damages beyond $10B.
Seems odd, doesn't it, that an industry which claims to have higher safety standards than any other is considered too risky by the masters of risk analysis - the insurance industry.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
"Safety" is something created by man and enforced in an environment with an eye towards the bottom line.
I have been on many construction jobs and "safety" is important as long as the schedule or the GC's bonus is not affected.
I doubt there are "small" or "short lived" nuclear accidents.
I doubt there are "small" or "short lived" nuclear accidents.
Well, maybe not those involving the fissile material, but nuclear power plant "events" happen with surprising regularity, like the cooling tower collapse at our little VT nuke last year.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Was the collapse due to....
Bad luck?
Substandard construction?
Substandard maintenance?
No one is telling?
The nuke owner, Entergy Nuclear, and the operator said they were "surprised" by the sudden collapse of the wooden structure.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Almost all industrial cooling towers are wooden.
And, by the way, that $700B was just the first installment. Several analysts have said that the total is $9 or $10 Trillion. But what's a few bucks among friends?
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
"not much" should be the answer.
<!----><!----><!---->
I refuse to accept that there are limitations to what we can accomplish. Pete Draganic
Take life as a test and shoot for a better score each day. Matt Garcia
A typical electric water heater is 90.4 to 95% efficient. Let's call that 92.7% on average.So 1.71/.927 = 1.84 cents/gallon.So to wash a load of clothes costs 0 at your house to heat the water, cuz yer too cheep.
Edited 12/31/2008 3:47 pm ET by Dam_inspector
A typical electric water heater is 90.4 to 95% efficient. Let's call that 92.7% on average.
So 1.71/.927 = 1.84 cents/gallon.
The question wasn't "what does it cost to heat and store a gallon of water" but just what does it cost to heat it.
Electric tank-type water heaters have a 98% heat transfer efficiency, so that cost should be:
1.71/.98 = 1.74 cents/gallon
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Who cares what the question was, this is Breaktime.
So to wash a load of clothes costs 0 at your house to heat the water, cuz yer too cheep
Ya got that rite, both inlets hooked to cold water, washer set on warm/warm; but somehow it aint never warm?
A real gallon of water weighs ten pounds.
<<<"A real gallon of water weighs ten pounds.">>>That's some heavy water!
Ron's profile says N.S.
Imperial at 10# sure makes more sense than the confusing 128 ounces (fl) which is not 8# but 8.33#???
Heavy water is only 9.25#/gal U.S., 11.1#/ per 'real' gallon.
Edited 1/4/2009 10:13 am ET by junkhound
Since the envelope/container of that gallon wasn't mentioned, it was logically ignored. Besides, he didn't ask what it would cost to account for the loss in any particular container ... just what it takes to raise the temp of the water.
Tank loss, generally is very small ... relative to the cost of raising the gallon of water. Besides, tank loss will vary depending on how much time you take to raise that gallon up to temp. Since this was logically left out of the equation and the impact is minor anyway ... it's not worth making a big deal out of it. Duh.
VERY little if that electricity is used to run a pump through a solar water heater. :)
.... eh maybe not in S. Carolina ... do you have sun there?
Not to get too far off the original question, but how much does it cost to heat a gallon of water with Natural Gas? I'm not sure how my gas is billed, the wife does the bills. Its either in Therms or Cu Ft.Pick a number that sounds reasonable and do the math.I'm just wondering how much a 15 minute shower costs in real dollars.
gonna start charging the kids?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
That is precisely what I thought this thread was about from the beginning...:)
What kind of shower head do you have, and what is your preferred water temp?
OK ... so 8.33 Btu/gal/Fdeg
Assuming a 55 degF Main water Temp and a shower of say 110 degF temp (it may be 115 deg). Remember, it doesn't matter what your tank temp is for this calc; your tank might be at 120 degF or 130 degF. For the dude that is concerned about other losses: this ignores pipe losses for arguments sake.
If you use a shower head flow rate of 2.5 gpm (the modern standard; an old one could be 4-6 gpm) and a shower duration of 10 minutes (way too long in my opinion, but people routinely do it), this requires 458 Btu/Gal to heat the water; 25 gallons per shower; 11, 454 Btu/Shower.
Heat it with gas at say 80% efficiency, that is 14,317 Btu of gas or 0.14 therms.
At $1.20 per therm, that is $0.17/shower ... times 30 days ... $5.15/month/person.
You can use a spreadsheet to adjust values and recalculate this. 17 cents per shower doesn't seem like much ... but it is the repetitious use that adds up. I think a 5-7 minute shower is more than reasonable (IMO); I can take a shower in under 2 minutes easily.
If you don't have a modern low flow shower head this cost could double. If you get a Jet Stream shower head at 1.5 gpm, you could save 40% more. They are very nice shower heads ... I've been 'testing' them with various clients (including the teenage daughters from heck who take 40+ minute showers!!!) ... and I really haven't had a negative reaction ... in fact the teenage daughters (not mine) didn't want to give it up. Plus you save water ... in some locations, water can be pricey (plus it's a good thing to do anyway).
Another good way to save hot water cost's if you have space to install it.http://www.gfxtechnology.com/VGFX.html
Intriguing ... but I'm unsure of exactly what it is ... Is this a wastewater line HX to preheat hot water? Why do you say if you have the space to install it ... looks like it takes up very little space ... unless I don't understand something ... see below.
I'm not impressed at all by the website. A lot of talk w/out explaining what they are really talking about. New unit, old unit, patent/product fraud/infringment ... yet they don't actually say what it was intended to be used for. I'm interested in cutting to the chase and finding out more about this product. Can you share more info?
The part about the LEED certified vs. Energy Star stuff was really confusing. Not sure of what the point was they were trying to make. Whoever compiled that specific site didn't do a very good job of communicating information. Maybe I'm being blunt, but that is the way I see it and I've read thousands of technical reports, summaries, etc. They sorely need a technical editor. No offense intended, but if they want people to 'log in' and 'turn on' their website and understand what they are saying, they need to speak clearly and suscinctly. ... one of my pet peaves ... sorry to get on my soap box.
Edited 1/4/2009 1:07 pm ET by Clewless1
> Why do you say if you have the space to install itNot much space if you have a shower built on a slab.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Is this a wastewater line HX to preheat hot water?
Yes. It's a copper drainline with coiled copper cold water supply line to the water heater. It transfers some waste-water heat to preheat the incoming cold water and instantly recycles the heat back into the shower flow.
Obviously, it works best on a first-floor shower over a full basement with water heater in the basement. It could be installed on a second floor shower in new construction or possibly renovation, but any distance from the water heater would cause line losses and reduce the efficiency.
People used to make these themselves and now several companies produce them. The best ones have flattenned copper coils soldered to a large diameter copper drain pipe for maximum surface contact and heat transfer.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
I've always had in mind a tank that would catch shower water, with heat exchanger coils in the tank. Would provide for more efficient heat transfer.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
What Riversong said.
This might help explain.http://apps1.eere.energy.gov/consumer/your_home/water_heating/index.cfm/mytopic=13040
Also ... if you happen to have the teenagers from hell who insist on taking showers longer than say 10 minutes ... turn the hot water valve off on the tank during the showers to remind them that this is an important issue and that squandering energy/water for no reason is not a reasonable thing to do. You only have to do it once or twice.
Another alternative is make them pay for the excess energy ... lessons in economics can be good too. I had a client turn her daughters off to 'encourage' them to curb their appetite ... it's working. Young people often think that since 75% of the earth is H2O, that it is "plentiful" ... but most of that is salt water and it costs to drill, pump, and treat water. Much like energy ... it needs to be managed.