I've been looking into on demand hot water heaters for my house. Due to the way it's built, I have two of them, one of which, only supplies hot water to the master bathroom. My house is all electric, and I found that the savings of a mere $20 per year, simply doesn't justify the cost of the on demand unit, and the cost of having the extra electrical circuitry installed to handle it. The Home Depot employee that I was talking to about the on demand units showed me an alternative - a timer for the hot water heater for a mere $40. I got it installed yesterday, and now it only comes on for three and a half hours a day - about an hour before I get up in the morning, to the time I leave for work. It can be overridden if necessary by flipping a switch. When I hopped into the shower this morning, the water was actually hotter than what it normally is, due to the heater freshly reheating the tank. :mrgreen: I'll be curious to see how much of a change it makes on the electric bill. If it looks good, I'll put one on the second hot water heater that supplies the rest of the house. I'll let everyone here know how it does as well.
In WA St, there is an energy savings program that Puget Sound Energy offeres for all its customers. one of the services is Peak demand water heater cycling. its supposed to save about $79 a year (realize we pay one of the lowest electrical rates in the country) although its voluntary program they encourage everyone to participate. its also one of the few items in the program that is free. (they also offer window caulking and hot water heater blankets free also. everything else costs money)
this energy program has been here for years. if you dont have it with your local power company, then maybe you should suggest it. i built my house in 1990 and the program was in effect then.
.0619 cent's a kilowatt and I'd still consider it. But the payback time on $40+ will take a while, maybe better off financially to wait till the company provides it free. Which will probably happen this winter or next spring.
actually the water heater is the 2nd biggest drain on your electric bill after the fridge in some houses. BUT many new energy saving refrigerators will use less than the water heater. obviously that wouldnt apply if you have electric heat, but the savings at 5.5/kwh is 79$ a year for low usage. another thing to think about, if you work unusual shifts and your hot water demand is at other than normal times, you might need to adjust the timer after its installed.
My wife and I are building a lake house and intend to use on-demand water heaters. The intial cost is a little higher, but since we'll use this house only a maximum of about 4-6 days per month it makes a lot of sense. We haven't decided if we'll use electric or propane out there...Electric would be more convenient, but we'll probably need propane out there anyway. We'll definately need to try to find the most energy efficient fridge we can too since it will run a lot when we're not there. Wanted to try to find an inexpensive solar system for those continuous demand appliances, but there really isn't anything out there that we could recoup our costs on as far as I can tell. We'd still use the grid for intermittent use things.
Put in both the piping for propane and the wiring for electric. The extra cost when building is negligible and the convienence of having a backup is priceless.
Evan you need one of those Chev Silverado "hybrid" pickups with the onboard power generation capabilities. if your that far out in the boonies. That said there are some very efficient propane powered fridges on the market now.
Wife & I lived off the "grid" on a small Gulf Island for 10 years, generating our own power ( solar with inverters) and running a combination of generators depending upon the load requirement. In addition we ran propane demand water heaters which were activated by opening the hot water tap which in turn lit the propane, heated the water as it was being used but the down side was that if someone flushed a toilet or ran a kitchen sink tap the pressure would screw up the shower temp big time. Previously we have cruised in a sailboat down to Mexico and return with identical demand water heaters, solar power and a wind generator ( which was also supplied by a propeller trailed behind the ketch). The only problem with the wind generator was that if the wind speed was less than 8 knots the field winding current resistance would begin draining the battery instead of the other way around. After 15 years in the boat and 10 on the island we consider ourselves "expert" (drop of water under pressure)in the technology of the time. :lol:
I use solar water heating and it provides >90% of my hot water. I have a very well insulated (R-25) electric water tank (Marathon) with the heater elements wired through a timer. We leave the elements off and activate them only if necessary. We also have a ground source heat pump and the reject heat during air conditioning can also be routed to the water heater for free hot water. http://www.enerjazz.com/house/whsolar.html
Wow, there are so many variables. I would be interested in comparing a total shutdown to a setback, though I wouldn't know how to go about automating a setback on a standard house-unit water heater. Here's what I'm thinking: Just like the Prius takes more energy to accelerate from a dead-stop, it takes a lot of energy to heat a 50 gallon tank of hot water from room temperature to 120ºF. But in the case of a setback, you would throttle it back to, oh say 90ºF so the difference is only 30º rather than 50º. Another point to keep in mind is evening hot water usage. If you wash the dishes in the evening, you will more than likely have plenty of water hot enough for this task. However, as you are drawing water from the tank, cold water it refilling the tank. Since the heater is not on, the overall temperature of the tank is dropping. Fast. Now when the heater kicks on in the morning, it will have to get that entire tank up to temp from a much colder (possibly even below room temperature) starting point. Just some thoughts.
As Tony said, many variables. Gas on-demand water heaters are much better than electric ones as they can boost the temp much more quickly. But, you can't run gas lines inside wall cavities (at least not in VT) so the tank needs to be near an outside wall or the pipe must be exposed. To avoid Canuck's "flush" problem, make all the feed lines in the house 3/4 or 1", not the standard 1/2". Tee off the feed with 1/2" to the use points. The "flush" problem is not specific to "on demand" water heaters. As for Evan's lake house - if you are only going to use it 4-6 times a month, how about a very small and efficient fridge for the stuff you want to leave behind that has to stay cold and a larger one for the time you are there. It really makes no sense to keep a big fridge cold and mostly empty for weeks on end.
Actually, in my case, my master bathroom is part of an addition to the original house. It has it's own dedicated plumbing, complete with its own hot water heater. I use hot water out of that bathroom only once per day for my morning shower. The rest of the time, it sits idle, cycling as necessary to keep the water hot and ready. It's located in the closet, and this room is typically quite warm in relation to the rest of the house. One immediate difference is the temperature of the water. Since it's freshly heated, it is actually hotter coming out of the tap, at the same setting, then before the timer was installed. I'm using less of the "hot" side of the shower's water control to maintain a comfortable temperature. With as hard as my water is, I can hear both of my hot water heaters, when I am near them, when they are heating. The one in the master bath has already cycled back off before I'm ready to hit the shower. Wiring the timers up is easy. Setting them up is even easier. They are mechanical units, that have adjustable switch toggles on them that you manually attatch to the dial to cycle the switch on and off. You can set up, up to six cycles on the dial. If I do the main unit, I'll have two cycles on it, instead of just the one on the master bath unit. One for the morning, so that I can run the dishwasher, or load of laundry while getting ready for work, and one in the evening to have hot water readily available for whatever it is needed for. Being single, I have the luxury of really tailoring the heaters to be up and running, only when I actually need them.
bruceha_2000: Yes you are correct under normal circumstances but I neglected to complete the information that our water pressure was supplied by a 12V pump through a pressure tank. Same thing on the boat.... oh the joys of living away from urban conveniences.
