LPG Tankless vs. Electric Water Heater

[_RaT_]

Yes, but how many times a day does a tank water heater turn on when you are not home? Ours kicks on halfway through my shower in the morning and stays on for about five minutes after the shower is over. Then it sits there all day. I have never heard it run during the day or night when no one is using hot water. I think if you are frequently not going to be home for a few days at a time, have a vacation home, or live in a restricted water use area, tankless would would make good sense. But for us, home every day, showers in the morning and laundry and dishes at night, a tankless has little advantage over a tank unit.

A poorly insulated one will kick on more frequently, but todays closed cell foams are very well insulated compared to the old fiberglass ones and the need to reheat the water is much less.

 

[BobRip]

That's my intuitive feeling but several industry pros have appeared in this thread saying 'it depends...' so I'm still trying to learn both sides of the issue.

That's the issue , I have low usage in this mild climate so economy measures might be pointless. I can't decide. Maybe there is little opportunity for a saving.

The gas bill for September (when the cabin was vacant and we used little space heat) was $30. It paid for maybe 30 individual showers and 5 loads of laundry. (We weren't there full time). Spring and fall with the cabin occupied are about $65, and a couple of winter months just over $100, with most of that probably for the cabin's space heat.

Looking at this, I see your point that the conversion cost for these water heaters might never be recovered considering so little potential savings.

I wonder if one that serves just a washing machine could be smaller. Also whether the washer needs instantaneous full temp. I was thinking of a simple through-the-wall vented unit (concentric cold air inlet surrounding the exhaust) and installing it myself, so the cost to replace the existing heater shouldn't be too much.

I hadn't thought of cutting a peephole. Good idea! Maybe that's all I need.

CurlyDave, I didn't mean to hijack your thread!

Interesting that two of the quotes that are attributed to me were not written by me. Is the system making mistakes somewhere?

By the way, I see the point of the long payback. You might have a shorter payback if you used electric and just turned it off when no one was going to be there.

 

[_RaT_]

That's my intuitive feeling but several industry pros have appeared in this thread saying 'it depends...' so I'm still trying to learn both sides of the issue.

That's the issue , I have low usage in this mild climate so economy measures might be pointless. I can't decide. Maybe there is little opportunity for a saving.

The gas bill for September (when the cabin was vacant and we used little space heat) was $30. It paid for maybe 30 individual showers and 5 loads of laundry. (We weren't there full time). Spring and fall with the cabin occupied are about $65, and a couple of winter months just over $100, with most of that probably for the cabin's space heat.

Looking at this, I see your point that the conversion cost for these water heaters might never be recovered considering so little potential savings.

I wonder if one that serves just a washing machine could be smaller. Also whether the washer needs instantaneous full temp. I was thinking of a simple through-the-wall vented unit (concentric cold air inlet surrounding the exhaust) and installing it myself, so the cost to replace the existing heater shouldn't be too much.

I hadn't thought of cutting a peephole. Good idea! Maybe that's all I need.

CurlyDave, I didn't mean to hijack your thread!

California, what great comments you made. I have to agree with your comments here. There is more to this then the hype we are presented with. It may well come down to analyzing our needs and even where we live to arrive at an educated decision. If a high quality tankless can deliver a energy savings over 15 years, you have to make some decisions, if it does it in 5, that may be another story. I really enjoy trying to be as energy independent as I can, but there is a monetary and a convenience factor to be considered. I'm still thinking about replacing my Rinnai 2424 with a tank, but I am still thinking thanks to all the great comments here.

 

[Doc_Bob]

Yes, but how many times a day does a tank water heater turn on when you are not home?

If you want to know, after it shuts down turn it off, and when you come home eight hours later, see how warm the water is during your just got home shower. I think you will discover it is way too cool.
Bob

 

[kenmac]

If you want to know, after it shuts down turn it off, and when you come home eight hours later, see how warm the water is during your just got home shower. I think you will discover it is way too cool.
Bob

That depends on where the water heater is located. A water heater (tank type)that is inside will still provide enough hot water to take a shower that afternoon ,if that water heater was turned off when you left for work that AM. Provided that ,the water was up to temp. (around 130- 140 deg) when it was turned off.

 

[California]

Interesting that two of the quotes that are attributed to me were not written by me.

Not a system error, but a cut-n-paste error by me. Sorry. I should have cited kenmac on the quotes after the first.

Thanks, everyone, for your valuable comments. I'm learning a lot as this thread evolves.

 

[CurlyDave]

A water heater (tank type)that is inside will still provide enough hot water to take a shower that afternoon ,if that water heater was turned off when you left for work that AM.

If the heater is located inside, all of the energy "lost" through the walls of the heater is re-used in heating the house. It is not thrown away, it shows up as a reduced heating bill.

Even though electricity costs more than gas or LP, an electric tank water heater can be located anywhere in the house -- it needs no vent and no combustion air.

 

[Doc_Bob]

That depends on where the water heater is located. A water heater (tank type)that is inside will still provide enough hot water to take a shower that afternoon ,if that water heater was turned off when you left for work that AM. Provided that ,the water was up to temp. (around 130- 140 deg) when it was turned off.

You are so right. I live in Wisconsin. No one has there water outside. When I lived in Southern California (in the 60s), all of them were located in ventilated "closets" on the outside of the building.
Bob

 

[DUMBDOG]

Our local co-op has a program where they can shut down your electric water heater during peak usage periods, they then give you a credit of up to five dollars per month on your bill. We have yet to notice the effects of this upon our hot water supply. This would reduce the savings of the tank less heater. The cost difference in units, electrical demands upon the breaker box or the venting requirements of the propane units that I was looking at is the reason that we went to the standard heater. We also have the unit turned off for about seven months of the year.

 

[Alan L.]

The current price of LPG is far less than $3. Of course, the price of LPG is much more subject to market fluctuation than electricity. Another thing to consider when projecting costs is the fact that tank models have a "standby" cost that tankless doesn't. In tank models, there is a cost in keeping the water hot all the time until it is ready to use. In a tankless, the water isn't heated until ready to use. On This Old House, Richard Trethewey made this contrast, "It's like keeping your car engine turned on and idling all day and night, due to the chance you might need to jump in and drive it."

I have been so pleased with my Takagi that I would never consider using anything else.

My plumber called today, getting ready to rough in the plumbing. He highly recommends the Rinnai tankless for LPG and has put in quite a few. I had settled on a high efficiency electric, but have now decided to add $1000 to my construction cost and use the 8.5 gpm Rinnai unit. I found that LP tank rental is $63 per year for a 250 gallon tank. Right now LP is $2.05 per gallon, but I am told it is usually less in the summer, and thats the best time to fill it up.

I still think the energy savings are marginal and the payback probably fairly long. However, this gets the hot water heater out of my attic and onto the exterior wall of the house, in the back, next to my shower. Plus, there will be remote controls in the bathrooms, to select the water temperature needed. And, at least the manufacturer claims, the tankless is supposed to last twice as long as a regular tank heater and won't flood the place when it goes out.

The placement will be 50 feet or so from the kitchen and 60 from the utility room, so there will be some wait times there, but I really don't want to spend another $1500 on a second unit.

So, in the duration of this thread I have changed from no LP and no tankless to LP and tankless. I hope this is the right decision.