mailnride1 said:Someone needs to invent a hybrid Hot Water system that has a tankless heater at the water main, and also a smaller electric powered heater right at the shower or sink where the hot water will come out. When you turn on the hot water, the electric heater turns on first, heating water right near the shower, once the tankless heater catches up, the electric one shuts off, either by timer or thermostat.

This is a similar principle to hybrid electric cars like the Prius that use gas and batteries when either one is most efficient (electric to start moving, gas on the highway).

The best energy savings would come from waste water heat recovery...using the recovered energy to assist in heating the home or preheat the water before it enters the water heater.

mailnride1 said:Someone needs to invent a hybrid Hot Water system that has a tankless heater at the water main, and also a smaller electric powered heater right at the shower or sink where the hot water will come out. When you turn on the hot water, the electric heater turns on first, heating water right near the shower, once the tankless heater catches up, the electric one shuts off, either by timer or thermostat.

This is a similar principle to hybrid electric cars like the Prius that use gas and batteries when either one is most efficient (electric to start moving, gas on the highway).

Already done. Here's an example: Eemax link

I've set up two 9.5kW units under my kitchen sink (the baths are directly adjacent to the main water heater). The first raises the incoming HW temp from room temp to 125-130F. Yes, I like it hot - and everyone in my house knows that hot is d@mn3d hot at the kitchen sink. I have a second single-temp faucet which takes that 130F water and raises it to 190F. Once the main HWH water hits the first unit, it shuts off (thermostatic control). I get instant regular hot water, plus instant - and capacity unlimited - near-boiling water. I can fill a stock pot with a gallon and a half of 190F water for pasta in about 1.5-2 minutes. By the time I measure the pasta out, it's already boiling - and I've heated it at nearly 100% efficiency, instead of the 35%+/- efficiency of the gas stove I use.

If you really want to get more efficient, especially if you like long showers (guilty!) - go get one of these grey water heat exchangers and put it on your showers where you have the space. I don't have one, but plan on putting one in when I remodel.

By the way - an alternate, though less efficient, way to do the instant hot water thing would be to put a small (5gal) tank heater after the whole house instant heater, then install a heated loop system that circulates the hot water to all of your faucets. It would likely be cheaper than putting in the POU heaters at each faucet. You have some heat loss in the system, but even that can be minimized.

EDIT: for those of you who fear I might be a little too green, I'll admit here that I have removed the aerator from the kitchen faucet, the flow-restricter from my shower head, and I have a 5 gallon flush toilet (two actually). Of course I'm cognizant of my usage and don't waste water or energy for wastefulness sake, but I refuse to accept second quality performance - and I'm willing to pay a little extra for it.

How safe is electric water heater? It will get old and rusted.
What happens if there's short circuit while you take a shower?

expert5186 said:there's a tremendous amount of heat lost through those vents especially on tankless heaters.

Actually, there isn't. Modern gas appliances are regularly better than 80-85% efficient, and some furnaces are at 98% AFUE efficiency. There really isn't much to extract from the exhaust stream at that point.

mdaily - electric water heaters are safe. The pipes are generally connected to ground, so the short path is never through you in the shower.

Overzeetop said:mailnride1 said:Someone needs to invent a hybrid Hot Water system that has a tankless heater at the water main, and also a smaller electric powered heater right at the shower or sink where the hot water will come out. When you turn on the hot water, the electric heater turns on first, heating water right near the shower, once the tankless heater catches up, the electric one shuts off, either by timer or thermostat.

This is a similar principle to hybrid electric cars like the Prius that use gas and batteries when either one is most efficient (electric to start moving, gas on the highway).

Already done. Here's an example: Eemax link

I've set up two 9.5kW units under my kitchen sink (the baths are directly adjacent to the main water heater). The first raises the incoming HW temp from room temp to 125-130F. Yes, I like it hot - and everyone in my house knows that hot is d@mn3d hot at the kitchen sink. I have a second single-temp faucet which takes that 130F water and raises it to 190F. Once the main HWH water hits the first unit, it shuts off (thermostatic control). I get instant regular hot water, plus instant - and capacity unlimited - near-boiling water. I can fill a stock pot with a gallon and a half of 190F water for pasta in about 1.5-2 minutes. By the time I measure the pasta out, it's already boiling - and I've heated it at nearly 100% efficiency, instead of the 35%+/- efficiency of the gas stove I use.

If you really want to get more efficient, especially if you like long showers (guilty!) - go get one of these grey water heat exchangers and put it on your showers where you have the space. I don't have one, but plan on putting one in when I remodel.

By the way - an alternate, though less efficient, way to do the instant hot water thing would be to put a small (5gal) tank heater after the whole house instant heater, then install a heated loop system that circulates the hot water to all of your faucets. It would likely be cheaper than putting in the POU heaters at each faucet. You have some heat loss in the system, but even that can be minimized.

I am HIGHLY skeptical that you are actually saving anything beside time with your setup over a traditional main tank system, . In fact your setup probably is costing 2-3-times what a traditional single gas heater setup with the appropriate tank size for your housew ould cost you! Have you ever done ANY comparisons? Instant heating with electricity is by FAR the most inefficient way to at BTUs to water. Most modern gas water heat systems have efficiencies that near 80% overall. Compare that to your instant healer solution which runs less than 28% BTU conversion on average assuming you have an thankless model. Efficiency in a tankless water heater is only achieved by these who use water infrequently 2=3 times per day. Otherwise a simple timer on your traditional water heater will save you far more money than any tankless design.

Actually 4.3 gallons per minute is not bad (not quite as good as the Takagi though). Keep in mind that you still mix it with cold water at the shower head as few of us really want to shower with 140 degree water. 4.3 gallons would be adequate for most 2 bath homes.

I installed the bosche the op linked. It's a great water heater. All you have to is install the water line. No electrical connection needed.

The problem is the water lines are located on the bottom of the unit. Most water heaters have the lines on top of the water heater. So I had to hire someone to install just cause I didn't have the experience in soldering and lengthening copper lines.

cnIsfg said:I am HIGHLY skeptical that you are actually saving anything beside time with your setup over a traditional main tank system, . In fact your setup probably is costing 2-3-times what a traditional single gas heater setup with the appropriate tank size for your housew ould cost you! Have you ever done ANY comparisons? Instant heating with electricity is by FAR the most inefficient way to at BTUs to water. Most modern gas water heat systems have efficiencies that near 80% overall. Compare that to your instant healer solution which runs less than 28% BTU conversion on average assuming you have an thankless model. Efficiency in a tankless water heater is only achieved by these who use water infrequently 2=3 times per day. Otherwise a simple timer on your traditional water heater will save you far more money than any tankless design.

The losses a traditional water heater suffers is from heat loss from the tank as insulation is not 100% effective (not even 50% effective...). Your tank is losing heat and needing to keep the water hot during the majority of the time that it is not being used. Even with a timer, there is heat lost while the water is not being kept warm. And when you are not home (like on a trip or vacation) you continue to heat the water unless you take the time to shut it off which few people do. With a tankless water heater, no energy at all is used when the water is not flowing.
You will save money and energy using a tankless water heater (regardless of use of timers)-- period. That is NOT debatable. The question is whether the payback makes it worth it or not.

cnIsfg said:Tankless water heaters are OK for some one or two personal living situations but currently they are far from being viable system for larger families. In addition they waste a LOT of water unless you also have a reclamation system to capture unused water that is usually discarded as waste water while you are waiting for the tankless units to produce hot water.
Have you ever used a tankless water heater? You are sadly mistaken with both of these arguments.
1) With a tankless water heater you never run out of hot water. Very nice for larger families. I could run three showers all day long with mine.
2) There is NO wait for hot water. 185,000 BTU (Takagi) will instantly heat the water. That is why these water heaters are often called "instantaneous water heaters".

kenmarks said:cnIsfg said:I am HIGHLY skeptical that you are actually saving anything beside time with your setup over a traditional main tank system, . In fact your setup probably is costing 2-3-times what a traditional single gas heater setup with the appropriate tank size for your housew ould cost you! Have you ever done ANY comparisons? Instant heating with electricity is by FAR the most inefficient way to at BTUs to water. Most modern gas water heat systems have efficiencies that near 80% overall. Compare that to your instant healer solution which runs less than 28% BTU conversion on average assuming you have an thankless model. Efficiency in a tankless water heater is only achieved by these who use water infrequently 2=3 times per day. Otherwise a simple timer on your traditional water heater will save you far more money than any tankless design.

The losses a traditional water heater suffers is from heat loss from the tank as insulation is not 100% effective (not even 50% effective...). Your tank is losing heat and needing to keep the water hot during the majority of the time that it is not being used. Even with a timer, there is heat lost while the water is not being kept warm. And when you are not home (like on a trip or vacation) you continue to heat the water unless you take the time to shut it off which few people do. With a tankless water heater, no energy at all is used when the water is not flowing.
You will save money and energy using a tankless water heater (regardless of use of timers)-- period. That is NOT debatable. The question is whether the payback makes it worth it or not.

I am not sure where you figures originate, but unless you ae buying off the back of a truck somwhere most modern gas tank water heaters have a BTU efficienty of at LEAST 80%. Most states mandate at least 60% efficiency to pass code.
Yes tankless water heater will save money in SOME light use situations. However using a tankless more than 15 minutes TOTAL per day will result in a higher net cost vs a traditional system with timers. That is NOT debatable. Plus when you now add the cost of mandatory water recovery systems the total cost of ownership skyrockets.