... At least, that is what my calcs came out to. For comparison, my car averages around 14 KW from the driveshaft. Since most of us in the US are somewhat familiar with the kwh energy unit, this power rating is easy to work with: two hours of showers a week ? 40 kwh a week. Calc: 4.2 joules/ml*C Ground temp: 10 C Water temp: 40 C Flow rate: 160 ml/sec (typo corrected, thanks pjc)
Actually, using your assumptions (which sound pretty reasonable) I get 336 W, not 20,000. Still higher than I expected, but not as shocking: P = (4.2 J/gC) * (40 - 10 C) * (160 g/min) = 20160 J/min = 20160 J/min * (1 min / 60 sec) = 336 W You forgot that Watts = Joules/second, not Joules/min.
Hi pjc, Thanks for finding an error. The flow rate should be 160 ml/sec*, not per minute. So the power rating is indeed pretty outrageous. -- *Shower head flow rate of 2.5 gallons/minute
Wow. Yeah, you are right. That is pretty outrageous. I do like my hot showers, though.... Good thing natural gas is cheap.
When I was in nepal, and found out they killed a slow growing tree for my shower at a tea house, I stopped showering until I got back to Katmandu. You can get a good idea of how much energy your hot water is using by looking at your gas bills in the summer. Its not all that much when its plentiful natural gas. At least mine isn't that much.
That is an amazing, surprising number for me. Looks right though. I prefer to think of it in terms of therms , 40 kwh = 1.36 therms, so allowing for gas water heater inefficiency and line losses, about 2 therms a week, or 1 therm per hour of shower time which is about $1.00/hour. There are also 1.6 gallon/minute shower heads that feel good. If you are using electricity to heat your water, definitely worth considering. Check reviews first though, many of the low flow heads aren't very good.
Was that in February of 2009? I made a brief stop at the Katmandu airport on my way from Bhutan to New Delhi and smelled something funny there.
I think of it this way, 40kwh is about how much oil is needed to get your prius to go 50 miles. I'm not sure about exact figures, but it doesn't seem like that is all that much energy given that it is domestic and mostly burns to co2 and water. I'm more worried about the imported oil I put in my tank, but hey that's why we bought prii. In terms of money, think of how much more your cell phone costs a day than the hot water in your home.
No I was there earlier. Hiked up to Everest base camp from low levels. Once you get near the tree line, you don't really stink that much but everything grows slower. It is kind of strange realizing that things are brought up the mountains with human power. Energy is more valuable when you need to carry your fuel
My cell phone costs $10/30 = 33 cents a day, but I'm not the average cell phone user. Now that you mention it, that is approaching our summer natural gas usage cost.
My cell phone costs $29 every 2-3 months! $29 prepaid card gives me 360 minutes iirc. My hot water costs almost nothing,,solar heated, with a small parasytic power cost, with demand gas fired heater if it is not hot enough. Icarus
Sorry, I don't remember what model I had, that was in a house we had 15 years ago. The water company in San Jose gave them away during a water shortage. They were small, solid brass with chrome plated finish and mixed air with the water. I checked the flow with a stopwatch and bucket, it was close to it's rated 1.6 gpm. I think your best bet is to read reviews. The one I had also had an on-off control on the shower head.
I think I will buy this one: Amazon.com: Delta Faucet 75152 Water Amplifying Adjustable Showerhead with H2OKINETIC Technology, Chrome: Lenny Dee: Home Improvement For now I heat with electric, but if I can find an installer who does not try to charge me my physician hourly rate I'll switch to NG. Our ability to conserve energy and decrease emissions is pretty amazing. From the following: Switch to NG (69% efficient boiler, ~ 2/3rds carbon intensity of coal) from Coal (30% efficiency); Decrease shower time 25% Use 1.8 G/min instead of 2.5 G/min shower head I'll decrease CO2 emissions (conservative estimate) to 0.67*(30/69)*0.75*0.72 = 15% of before! Coal pollution emissions go down much further. A new house could install a $1000 heat exchanger that would recycle 70% of the water heat, and then 5% of the CO2 and grid emissions would exist instead of what so many of us do now. Total cost ? Recouped over time. Exercises like this remind me over and over that so much low hanging fruit to decrease our energy and footprint exist and should be exercised before expensive production of clean energy is undertaken. I'm looking forward to bringing my home electric consumption that includes cooking down to below 100 kwh/month. 50 kwh/month seems like a modern day lifestyle minimum, but I'm wasteful.
Seems like the power consumption can be WAY higher. For instance, CA gets a bunch of its water via diverting Colorado River water (and/or other far away sources). I can't believe 20-30 gallons can come hundreds of mile (pumping up a bunch of mountains and sliding back down) in some cases, and THEN add the heat, can be done for such a low figure. I'm sure many get there water pumped from shorter distances, but it's a factor worth considering. .
Definitely with our drought last year, and the aquifer and rivers not recovered, the water is more valuable than the natural gas. I wasn't saying the showers were fine for the environment, but compared to much of what we waste the natural gas to get us hot showers are not high on the list. Water and natural gas do come together in many places though. Often fracking is wasteful in water.
Note, that is much more expensive than my natural gas. It was $8.14 last month, for two of us. That includes the natural gas for my gas cloths dryer and stove, not just the showers and hot water for washing. Water and Sewage was 24.49, that water and water treatment are much more valuable than the energy to heat the shower down here.
