Anyone know of good sites that break down the energy and dollar saving between an Electrics Hot Water Heater (40 Gallons) and a Tankless system.
Assume the option on the tankless would be Natural Gas or Electric.
Has anyone made the change over?
How do you like it?
What kind of savings have you seen?
I am trying to estimate the pay back and I think it might only be a few years.
Jim
For gas units, the Bosch and Rinnai units are very good.
I would guess the savings at $250-300 per year for the typical family of 3 or 4.
That, of course, needs to be compared, not to the cost of the new tankless unit, but to the cost differential between a standard replacement and a tankless unit.
In my neck of the woods, you’ll pay an additional $1000 give or take for a tankless unit. ($700 vs, $1700)
At $250 savings per year, that’s a 4 year payback.
YMMV
Thank you, I just verified that the Gas Company will not tap the 20" main for the houses on my road.
I won’t do Propane, so I am down to electric.
Jim
I looked into this awhile back. Gas units typically provide almost twice as much HW per minute that electric. Unless you have a small house you’re probably going to want more than one electric tankless, the ‘point of use’ type installation. Don’t forget the installation cost, including removal of the old tank and rerouting of supply lines.
I just found out the units large enough for my house need a 200amp service. This is beginning to look like a bad idea.
Jim
I came to a similar conclusion, maybe when they become more common in the U.S., the cost will come down.
Well, I got the idea in my head as they put the 20" gas main in my road in October. I figured, cool, now we can get gas and I can slowly start replacing my electric water heater, stove & dryer with gas. Today I called to verify and found out that as the lay the 20" main, they make no provisions to tap off of them. :rolleyes:
I am still curious about the real savings between a standard Electric Water Heater and the equivalent tankless. The claims of 50% appear high.
Jim
But it’s not the price of the unit that’s making it look like a bad idea, but rather the service requirements. If it’s just a matter of replacing the service entrance with a bigger service box, it may not be that big a deal. If you have to have your power supplier upgrade to a 1/0 cable, it’s probably “free” to you. It’ll get expensive, though, if it’s determined that the power company needs to install a brand new transformer within 200 feet of your home. That part will probably be “free” to you, but then you’ve got to run new (probably underground) service to a new service entrance, and that’s where the price starts to grow. What the power company is trying to avoid is severe (greater than 5 to 7 volts, momentary) voltage drops that affect you and your neighbors.
I may have to do the same thing :(. The power planner said he’s willing to wait until summer to see if things get severe when everyone is running their A/C systems. Right now I’m the only one drawing A/C-type loads off of the transformer. On the upside, my gas bill dropped from $200 last year February to $8 this year February. It’s not even that cheap in the summer, indicating that my “free” hot water is so totally worth it! Electricity only shot up $50, so the heat pump is worth it too. I just don’t want an ugly transformer in my yard – no, not in the easement, but in my yard.
Funny you should ask. I just finished changing out my 40 gallon water heater for a tank less unit. Since my water heater was nat gas, I went with natural gas.
Issues:
[ul]
[li]A standard water heater has the water lines high, and the gas line low. The tank less unit has them all right next to each other, so you have to move the water lines down, and the gas line up. No big deal, you just have to tear into the wall and patch later.[/li][li]Here is the biggie. The tank less unit requires a 3/4" gas line. The existing for my water heater was 1/2" This required some rather complex re-plumbing of the existing gas lines under the house to do the change over. [/li][li]They don’t make a flex line large enough for the 199,000 BTU input of my burner, so I had to hard plumb the gas line all the way to the unit.[/li][li]You need an electrical outlet near the unit as it does require some (2A) of electricity to run the unit. I had to run a new outlet with a GFCI to near the unit.[/li][li]The unit requires a 4" vent. the water heater required a 3" vent. I was very lucky that my house had a 4" vent installed in the celling so I did not have to change that out.[/li][li]The unit was about $400 more expensive than a top of the line nat gas water heater.[/li][li]Water is not quite as hot coming out of the taps. Regardless of how hot you set the t-stat there is a limit of how many degrees the unit can heat. It is more than adequate, but I can’t get scalding water any longer.[/li][/ul]
I have not yet gotten my first gas or water bill with the new unit, I expect my gas bill will drop by $20-30/ month, but I don’t know.
I also expect a longer life out of the unit, but again I don’t know that for a fact.
If you want to do this job yourself, I would classify it as for an advanced DIYer. This was not an easy job. I had a contractor help me. I am capable of doing it myself, but it was lots easier with a second set of hands.
FWIW the guy at the plumbing store told me that this type of change outs start at $1000 for the installation. After completing it, I would bid it at more like $1500 if somebody wanted me to do it for them. It was a bitch.
About the electrical change out. Going to 200A service will probably require a new panel, as well as a new drop from the power pole. The drop is free, you will have to get an electrician to install the new panel, and run a circuit to where the WH lives. When I upgraded my electrical service this cost me about $1500.
All right, let’s look at some real numbers. A well insulated hot water heater will have an R-value somewhere around 24. That makes its U-value 0.04167 BTU/hr-ft2-deg F. Assume a 70 degree F difference between the tank contents and the outside environment, and a tank surface area around 40 square feet. That’s a cylinder 2.5 feet in diameter 5 feet tall.
Heat transfer to the environment is going to be 700.0416740= 117 BTU/hr. Converting this to watts we multiply BTU by 0.293 and ipso facto, our energy loss is 33 watts per hour, just about half as much as a 60 watt light bulb.
33 watts/hr * 8760 hours/year*Kw/1000 watts = 289 kW-hr/year. At 10 cents per killowatt-hr your tank loses $28.90 in energy per year. Even if you drop the R-value to 16 the losses only go up to $44/year, raise energy cost to 12 cents and you reach $50/year. It’s a long payback period if you compare it to a modern, well insulated system hot water tank.
And consider that during the winter the heat goes into your living space. Of course, during the summer it does too, which raises air conditioning cost, so I didn’t take a credit for winter heating or a debit for summer cooling. I figure it’s a push.
Off the top of my head, I don’t think your numbers jibe with Balthisar’s experience.
$8 bucks in Michigan for gas in a month? Daaaaaaaang. Could you elaborate on your set up? I’m fascinated and envious! 
I’ll be honest, from Balthisar’s description I can’t tell what he installed. It seems like he swapped from a gas fired central heating system to an electric heat pump, possibly with domestic hot water attached. Maybe he could elaborate a little more. I’d be more than surprised, nay, astonished, if he was paying $200 a month for hot water last February.
Here’s a cite. Homes that use a small amount of hot water per day get the most benefit, being between 24% and 34% more efficient than storage hot water units. Homes that use more than 86 gallons of hot water per day are 8% to 14% more efficient than the same usage with a hot water tank.
You can only get to a 27% to 50% increase in efficiency by installing a hot water unit at each hot water outlet. So, depending on how much hot water you use, you only have to figure what that increase in efficiency is worth to you.
Looking at it realistically, you have 20 times the energy in hot water going down the drain as you have leaking out of the sides of your tank, so limiting usage is way more cost effective than getting rid of the tank.
There’s a big difference in the efficiency of electric versus gas. Electric is much more efficient, because nothing goes up the chimney, but more expensive per BTU equivalent, so it actually costs more per gallon of hot water. Electric does have the potential of being able to be generated with carbon-neutral sources, so that may be important to you.
Thanks for the input everyone, I learned a lot today.
Actually carbon-neutral is important. My Solar Panels power most of our needs on average, but the damn Electric Hot Water Heater was not in the calculation.
As gas is not an option and the Electric Tankless looks like a poor solution for us, I am regrouping and I will be looking at replacing my Central Air unit instead.
I should have just got a larger Solar Panel System.
Jim
I have had mine for about 6 years now. $20-30 a month was about what I saved on the monthly electric bill after I made the switch, and I watched the electric bill for about a year. Shortly the one-year mark, my home had one less occupant so it was hard to make a fair comparrison at that point.
There’s another item in the woodpile that needs examination here,heat loss in transmission.A BIL was bragging about his new tankless.When I visited and used hot water in the kitchen,it took almost a minute to arrive.The bathrooms are further from the unit than the kitchen.I hear some people start the shower and then shave while the water warms.( Of course tanks suffer this too.I’m just amazed how many people don’t factor this into the equation.)
POU would solve the problem,which means multiple units/vents/services.
Do the tankless heaters have provision for anodic/corrosion protection?One of my electric tanks is now pushing 25 years;in this locale the norm for electrics is 7-8 years with gas being less.I flush the tank and replace the anode when needed.“L” copper gets pinholes in 18-20 years.What’s the lifetime of the tankless?
I too would like a little more description from Balthisar.What Exit?- It sounds like that 20" was high pressure transmission,where the only taps would be to a meter station for customer sale.PSE&G was a big customer through Jersey (probably still are,I’m retired ) but I don’t know if they distribute to residentials like many other utilities.Were it a distribution line they would have branched off for you.
Do you recall the contractor on the job?
Why won’t you “do” propane?
Yeah, my total gas use was $200, including heating the environment, not just the water. In the current setup, I no longer have a gas furnace, but a ground-source heat pump with a desuperheater for hot water. I know that the desuperheater is saving my significantly on the hot water because my gas use was only $8, whereas in the summer (with no heat), it’s usually $16 to $20, depending on the laundry load. So for $8 of gas in January (February billing), I got gas stovetop, gas dryer, decorative gas fireplace, and gas backup hot water. The additional cost of electricity was $50, so the bulk of my savings was in heat, not water. My water savings seems to be about $8 per month so far, since the gas water heater doesn’t need to fire. Here’s how that works: the desuperheater maintains water in a separate, electric water heater. This heater is not connected to electrical service, so it’s just a storage tank. It’s connected to my existing gas water heater cold water inlet. So any time I draw hot water, it comes from the gas tank, and is replenished with already hot water. Hence, it never needs to fire, except for thermal losses. Because it’s a gas tank, it has higher thermal losses than an electric tank (because of the flue), so it still has to fire once in a while in order to maintain temperature, but it never has to raise temperature. Of course, the more we use hot water, the less it actually has to fire. In my particular system, though, if I’m not heating/cooling air, I don’t get the benefit of the desuperheater, so there will be a few months here and there where I’ll be counting solely on the gas-heated water. Admittedly the biggest net savings was the gas heat, but my return on investment for the extra electric tank plus desuperheater is actually faster than on the ROI on the system as a whole.
That is a major point of dissatisfaction from consumers who have had tankless unit installed. You have to draw water either at a low volume or at a reduced rate in order to avoid pulling water through the unit faster than the unit can heat it. I recommend using 3/8 inch cpvc or similar to help restrict flow.
It helps to move the unit to the point of use, but obviously you can’t do this for every usage point in a home unless you go for smaller POU units.
That’s why on-demand systems need to be carefully thought out, otherwise consumers will be unhappy and blame the technology when the implementation is really at fault.