Hybrid Water Heater vs. Tankless Gas
A cousin called me today with questions about her water heater. Her old electric is dying, and she wondered about these new hybrids. They’re essentially standard electric water heaters but with a small heat pump unit on top that utilizes room air to heat the water as much as possible. They do have elements to cover high-demand periods, but offer a number of settings to meet demand and/or minimize energy consumption. GE’s offering is $1600.00 vs $450.00 for its 12-year 50-gallon standard electric, but operating expense is $200/year vs $500/year. If this $300 savings is realistic, the payback would only take 4 years–less if you collect the tax rebate. Installation is no different from a standard model, though if it’s to be in a closet, it requires a louvered door to assure enough air to the heat pump. Tankless gas units claim a fuel savings of only $100/year. Given the higher install costs of a tankless vs. standard gas, its payback would take ten or twelve years, right? Should I still be thinking about a tankless for the house we’re remodeling or get one of these hybrids?
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The tankless savings over conventional tank is relatively small. I'd be surprised at a $100 savings annually for a tankless. The savings in the tankless will be in eliminating the standby loss of storing hot water in a vessel ... which is a fairly small value with modern insulated tanks. Most claims of 'big savings' are when people change really old water heaters for a tankless and high efficiency combined. Remember, you can get high efficient tank style water heaters, too.
As for the heat pump style ... there are two types, if I recall ... regular and exhaust air heat pumps ... which remove heat from otherwise wasted exhaust air and puts it in your water. The type I think you refer to ... takes the heat out of the air in your space and puts it in the water. If you are in a heating mode/climate, that means your furnace will make up all of that heat you used to put in your water heater. Since it is a heat pump, it's doing that efficiently, but you are still increasing your heat load in the house.
I'm not trying to discourage you, but make sure you understand what it is you might be buying. This will cut into your payback to some extent. Now this is only part of the equation. If you heat with gas, this might be OK. If you have a lot of a cooling season, it will be OK, too. This HP system isn't as simple as 'buying a water heater'; it has other ramifications ... is related to other energy systems.
Tankless generally is not necessarily a good choice for a house that normally/regularly uses domestic hot water ... best for the occasional use (e.g. the weekend getaway). They frequently oversell them on 'big savings' when that simply isn't the case. There is a time and place for all technologies and I advocate informed choices that make sense for the application.
That's a good point about the
That's a good point about the heat pump style heater impacting the hvac system, though I can't imagine that it would be a terribly large impact? My largest concern with it would be the presumed costlier maintenance. Surely the heat pump or its control panel may become problematic at some point.
Oh well, I'll keep mulling it over. At the rate I'm going on our house, I still have a year or more to decide. Maybe I'll encourage my cousin to go for it and then see how she likes it.
Heat pumps => overrated tech.
A heat pump that uses room air to heat water is going to:
1. Increase the heat load on the heating system. (May make sense in a cooling environment.)
2. The radiator of it gets cold, so there will likely be condensation.
TANNSTAFL: There aint no such thing as a gree lunch. Every BTU you put in that water tank came from somewhere. If the furnace is running it came from the furnace. It's a win ONLY if you are extracting heat from the house exhaust air.
BUT it's still a heat pump. Everyone I know who has a heat pump or house sized air conditioner, or walk in cooler seems to need major service every few years. Doesn't take much of that to eat up energy savings. Heat pumps have moving parts, and therefore are tools of the devil, and symbols of the anti-christ.
Tankless hot water heaters.
May make sense for either a seldomly used place, or a place with 5 teenagers. On the other hand with endless hot water, some people will NEVER get out of the shower.
Lot to be said for a roll of chicken wire, and 4-5 fiberglass bats around the hot water tank.
Consider the impact of a water heater heat pump on your HVAC operation.
50 gallons of water heated from 60ºF to 120ºF requires 24900BTU = 7.3KWh.
1 kWh = 3412.3 BTU
1 BTU = 0.000293 Kilowatt Hours
GE claims its hybrids require only 48% of the energy input of its regular water heaters, so more than half of heating must be coming from the heat pump.
In winter, your HVAC system will have to replace that heat to maintain the desired air temp in the house. In summer, your HVAC will have to work that much less to cool the house to the desired air temp. If annual heating degrees x days = cooling degrees x days you break even (assuming same cost per degree to heat as to cool the house).
It depends where you live.... If she is out in the country and the power goes out, both won't work at all.
You might a little hot water from the reserve in the Hybrid tank as long as the well tank/city pressure is up.
Bill
I have a tankless and it is a long time to pay off. I save about 120 a year on hot water costs. We have no complaints about it but time will tell! First we will see if it lasts the 11 years till payoff arrives, been 4 years so far. My wife likes the gained closet space now, that is why she loves it, haha! Other than that... it's a water heater, nothing special.
Hi, You might take a look at the info here:
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm#HeatPumpWater%20Heater
The last one "Wiinter use of Heat Pump Water Heater" describes a setup that helps with the issue of the heat pump water heater fighting with your furnace in the winter. It involves a little ductwork, and you have seasonally change a damper, but it seems workable to me.
The part on the heat pump water heater is a ways down in the document.
The video from Tom Gocze on installing a heat pump water heater is interesting and fun.
Gary
I recently installed a tankless hot water heater and am not happy with it. As the tankless system raises water temp a certain range, and not to a specific temperature, there are big problems with incoming water temperature fluctuations especially in winter, and especially in New England or other cold climates. The result is my hot water temperature fluctuates widely as the system first pulls water from basement pipes, then outdoor, underground pipes then from wherever its coming from beyond that. It also does not handle multiple loads well at all. I see no savings in my electric bill and cringe everytime I go to the faucet to wash my hands. I'm done washing by the time hot water even gets close to the sink, and I've just spun my electric meter for 120 amps of current. Not happy at all and am considering going back to a tank.
Tankless is the BEST
Tankless use ZERO energy while not in use. They don't RUST( a huge energy loss factor) Metal elements + water = RUST/corrosion period.
A tank style heater is a excellent debris trap (sand,dirt,sludge) drain a old heater and see for yourself.
Tankless water heater provide PRECISE computer temps of water.The must be sized for the demand of use.
These Opinions I am reading about tankless are simply false w/ no documentation. The tankless units provide ENDLESS supply of hot water when needed/wanted! Unlike a tank trying to keep up w/ demand.
The tankless is simply superior in everyway .like power,operational life,Maintains its energy rating etc...most people over temp the tank heaters they have .Then reach in the shower to turn on the cold knob to not burn themselves (wasting energy) because the tank will run out or someone else wants to take a shower next etc......The tankless can precisely provide a100 degree water temp ENDLESSLY.(no waste over heating the water just to cool it back down) See? this is real world facts.Just look @ the energy guide label for a 50 gallon electric water heater $540 yr. Tankless 141000 btu unit ,same sticker $94 yr.......ENDLESSLY! the other is LIMITED demand period.
You've been here 33 minutes and you're an expert on tankless water heaters already?
In most circumstances tankless heaters don't save any appreciable amount of energy. Modern tank heaters have very low standby losses, and tankless only saves significantly if hot water use is intermittent (as in, eg, a weekend cabin).
Tankless heaters cannot supply an unlimited amount of hot water. If flow exceeds the design limit then temperature falls off (leading the person in the shower to turn up the hot and get colder and colder). A tank, on the other hand, can supply large volumes of hot water over a period of a few minutes -- pretty much all most people need.
Tankless heaters are expensive, and do not have unlimited lifetimes. They're more complex than tank heaters and more likely to break down. The $$ equation rarely comes out in their favor.
One advantage of tankless is that they occupy less space. However, they generally need larger gas service and flue than the equivalent tank, so one cannot just remove a tank and slide a tankless in as a replacement.
I can't speak for all tankless hot water heaters, but my heater (bradford white, not sure of the model) never changes the temperature of the output. If you are trying to run more water than it can heat, it will simply restrict the flow of the water. In my house I can have two people showering at the same time with the heater set at 110 and you never notice a difference. If I turn on a third shower, there will be a reduction in flow to the showers but the temperature is a steady 110. We can run three at a time, but you won't have as much pressure due to the reduced flow. If I turn the thermostat up to 160, the flow from the water heater is pretty low, but it comes out at 160 degrees. I live in Montana, and our water comes out of the ground at about 45 degrees.
I don't think the tankless saves me any on my heating bills except when we are gone for the weekend or on vacation. When they are running they use a LOT of propane, but when they are idle they use NO propane. The best thing I like about ours is that when we have everyone trying to shower in the morning, everyone has hot water and we don't have to wait for the tank to heat up before the next person can get ready. Two weeks ago we had company and got 10 people showered and ready in 3 bathrooms in under an hour. With the old tank heater, you could get three very short showers, then you had to wait 30-45 minutes to get enough hot water for someone else to shower. We would have had to start showering at 4:30 am to get everyone ready in time...
If you are getting a tankless for the energy savings, I would think twice. You probably won't see energy savings unless it is a more occasional use situation (as mentioned above). If you like to trickle hot water a lot, tankless heaters don't trickle. You need a certain amount of flow before they kick on. If you are getting one for the convenience of everyone being able to shower in a short time, or the ability to change the temperature output at the touch of a button, then they are great for that. I do recommend that you check the temperature of your water when it comes into the house, as that will be a big determining factor on how much flow you will get at a certain set output temp.
And you are obviously a shill for the tankless industry. Most of what you said is not true at all.