I installed a Rinnai RLS75i natural gas unit at the end of July. I have finally received my first gas bill with the whole billing cycle with the tankless.
September 07 Bill: 16 therms billed.
September 08 Bill (Aug 13 to Sept 12): 12 therms billed.
12 / 16 = 0.75
Or, a 25% savings.
I would think as the weather gets colder, the savings would continue.
I do have a major hot water use this year that I did not have last year however that may skew things a little. My wife is 37 weeks in her pregnancy. Sometimes she literally takes 3 baths in a day. It helps her with the pain. Even with that I still was able to get a 25% savings.
As far as the experience goes ... pretty typical of other tankless units I think.
I can run two showers without a hitch. I do not notice any fluctuation in temperature at all. I think the tankless does a really good job of keeping the temperature the same regardless of the load. Temperature consistency has been great. Don't notice cold "sandwiches" during use at all.
There has been a time or two where I have run into low flow situations where the flow was too low for it to kick in.
Getting ready in the morning is great. Back with the tank, usually by the end of the 3rd shower we were out of hot water. That was tough when you have at times 6 people that need showers and baths. We typically would have 2 or three people shower, wait 30 minutes to an hour, followed by the rest. Now, we just shower. The hot water heater no longer runs our life. I would definitely recommend a tankless if you have a large family.
Also, back with a tank, when another person started to shower in the other shower, you would also have to "fight" for your share of the hot water by upping the hot water every minute or two until you were done or ran out of hot water. Now, when someone jumps in the other shower, I do nothing but shower. The temperature of my shower stays the same with the tankless. It is really nice.
Obviously seek a plumber to see if a tankless application is possible.
I had a 50 gallon "basic" natural gas tank prior. Nothing fancy, no special venting, etc. It was 8 years old when I replaced it. It still was working fine enough and probably could have lasted another 8 (who knows). As a family though, we were just tired of living as the water heater "told us" and so I decided to "convert".
And so, the big bang for me is the continuous hot water. The additional savings is just icing on the cake.
Last edited by TheOak; 09-16-2008 at 11:38 AM.
Nice. I'd like to know if that is cheaper to run then an oil-fired hot water heater, like a Bock.
Here's what I'm talking about: http://bockwaterheaters.com/Products...r_heaters.html
I had on of these back in my old house. During the summer months when my oil boiler was not running the level in the oil tank would hardly move. As I recall I used 5 to 7 gallons per month with two kids in diapers and of course, lots of baths. Oil is a very dense (high BTU) fuel and also burns very hot.
If I read the site right then, the residential models have an efficiency rating of .66. Gas based tankless units usually start at 0.80. So unless the cost of oil is super cheap and outputs that much more BTUs versus natural gas, I do not see a savings as far a monthly bill goes. Their first hour rating however appear to be great. Led above also states tankless is cheaper.
Last edited by TheOak; 09-16-2008 at 12:23 PM.
Gas can be more efficient and it is also a cleaner fuel. Yours with the PVC vent is probably a condensing unit, which is even more efficient. Those are nice because you can route the vent almost anywhere, not so with a fuel oil vent. I went through this exercise a while back with propane (LNG) and found that it takes 1.4 gallons of propane has the same BTU as 1 gallon of #2 Fuel oil. Back then I chose oil over delivered propane but I'm not sure that the numbers would work out the same way today.
Mine is not a condensing unit. Those are rated something like 0.95, but are super expensive. This cost of my unit including installation, is probably around the starting price of just the condensing unit itself, not including installation. My Rinnai R75LS natural gas unit is rated 0.82. I might get payback on my unit within 10 - 15 years or so. It is too early really to project though - could be more - could be less. I would never get payback on a condensing unit before it died. The general life expectancy of tankless units appears to be 20 years. Maybe by the time mine dies, the condensing units will be the norm and really cheap.
The test will be how it works on a cold snap in the middle of the winter when the incoming water might reach close to freezing. It's hard to get a good comparison unless you can also measure the water consumption, but an economy gas WH can run in the 60% efficiency range (there are better ones), so your numbers seem reasonable.
Important note - I'm not a pro
Retired Defense Industry Engineer
I agree, this winter should be very interesting. With that being said though, before I jumped on board with the tankless, I did ask for tankless references from the contractor. One guy I spoke to, who had two showers, said they did not notice a difference at all with both showers going. He was on a well too, where I am city water. Not sure which one would be warmer. He also had a smaller family though.
I see my worst case scenario as only using one shower. I figure however I am no worse off as with a tank. With a tank 3 people could shower, followed by a 30 minute to an hour wait, followed by the rest. With the tankless, person after person can shower, which should get all the showers done in the same time frame, if not sooner, as prior with a tank.
Thus far as know, I have had both showers going and the dishwasher too and have not noticed a change in the shower. Rinnai claims that for my model I can run three showers and a tap during the summer months and two showers during the winter months. I feel pretty confident based on my interviews and Rinnai's claims that during the winter I can crank out two showers during the winter. Time will tell ...
I'm glad that you are having great service out of your tankless. I have a wife and three kids that get ready every morning along with myself and I have yet to run out of hot water while taking a shower. I have a 40 gal. gas water heater. The first thing my wife does every morning is get up and load the dish washer, the kids get up and take turns taking their shower while my wife takes hers. (We have to full baths). Once everyone has their shower I take mine. Not once in the 15 years of living in this house have I ran out of hot water. Now when I was growing up, living in a house with four kids and two adults we ran out of hot water on a daily basis and with a 50 gal water heater. Go figure.
I've often wandered about going tankless. Thanks for your post.
Yes, this winter will be interesting ... the specs say I should be okay. It is good to hear your report of two showers. One contractor I spoke too, did not hire him for other reasons, was very informative. He stated that they were finding that the lowest gpm range for this area seemed to range from about 4.6 gpm to 5.5 gpm throughout the year. According to this calculator (select Flow VS Ignition) at 4.6 I should be able to handle two 2.5 gpm showers even if my water temperature is 40 F. Barely though, and there may be other factors that will kick in. Time will tell ...