WayneB
Elite Member
For a house or cabin that is hardly used, a tankless is much cheaper, this is the exception though.
One thing for sure I will be keeping track of the fuel cost and will know better next year at this time.
For a house or cabin that is hardly used, a tankless is much cheaper, this is the exception though.
Some conversion rates for oil and propane.
Propane conversions
1 gallon = 91,500 BTU
1 cubic foot = 2,500 BTU
1 pound = 21,500 BTU
4.24 lbs = 1 gallon
36.39 cubic feet = 1 gallon
Oil coversions
1 gallon kerosene = 135,000 BTU
1 gallon #2 oil = 138,500 BTU
1 gallon diesel = 139,200 BTU
1 gallon #6 oil = 153,200 BTU
The higher the fuel cost the faster the payback will be for the tankless and the more sense (and cents) the tankless makes to use.
please note how efficient each device using each fuel is.
if on avg 1 gallon of fuel oil has 34% available BTU's than propane but is 40% less efficient at burning that gallon of fuel vs propane, you have gained nothing by using the fuel oil.
dont forget to take the efficiency into calculating whats cheapest to run.
The higher the fuel cost the faster the payback will be for the tankless and the more sense (and cents) the tankless makes to use.
I know everyone has their opinions on these tankless W.H.'s
I've been in the plumbing/ gas businees for 25 yrs. For some reason I'am still not sold on tankless.I have been to several MFG. classes on these tankless W.H.'s Too many expensive parts that can & will fail. Not to mention water tubes that will stop up if not properly maintained.when they fire you are talking 199,000 BTU . compare that to a tank type @ 32,000 BTU. & Almost o maintance. Even at my cost . They are still expensive
The October 2008 issue of Consumers Reports magazine has an article on tankless vs tank type hot water heaters you might be interested in reading.
Average annual operating cost for tankless $330. Initial cost $800 - $1150
Average annual operating cost for high-efficiency 50 gallon tank $330. Initial cost $1400
Average annual operating cost for a standard 50 gallon tank $400. Initial cost $400
The payback period for a tankless is very long because its higher initial cost ... 15-22 years.
Operating costs based on natual gas.
I put in a tankless for $600 (just for the unit) and got a rebate from the feds for $300 of that. A basic power vent tank heater would have cost me about the same money to buy (actually $300 more considering the rebate). That's why I went with a tankless.
As far as fuel savings, I'm not sure how they figured that, since it would completely depend on your water usage. The more water you use throughout different times of day, the better deal a tank heater is. If you use hot water only a few times a day (as I do... mostly in the morning), the more energy you are wasting by keeping hot water on standby 24 hours a day.
The payback for a high efficient (car, heating system, hot water heater, etc.) will be greatest 1) the more it is used, 2) the higher the fuel cost and 3) the lower the initial price difference between a high efficiency unit verse a low efficient unit.
So a tankless makes the most sense if you use a lot of hot water and/or the fuel you use to heat water is high and/or the difference in price of a tankless verses a standard water heater is low.
The issue of complexity is something else. I personally lean towards the principle of "keep it simple" because one or two service calls can wipe out a lot of savings real fast! But than again, remember "the good old days" when cars weren't computer controlled and fuel injected? Remember when they had carbs and chokes? When was the last time you turned the key in your car/truck and it didn't start? The high tech cars of today certainly are a VAST improvement over those old cars. I could work on those old cars and had to on a regular basis. Cars of today I couldn't do anything with but the nice part of that is I've never needed to!
I would think the standby loss of a standard hot water heater would be fairly constant whether you use a lot of hot water or a little. You basically have a tank of 130 degree water sitting there all the time. So I don't think using hot water just a few times a day would have much effect positive or negative on the efficiency of a standard tank type water.
PS - I see some people are comparing propane costs. I just paid $2.98 per gallon for propane here in SE Michigan. Last year I paid $1.98. We use about 300 gallons a year. I have our tank topped off once a year. We use propane for drying clothes, hot water (20 year old standard tank type) and backup heat. Our primary source of heat is wood ... 3 cords/year.
Actually it is the other way around for a tankless heater... the tankless heater just saves you standby losses... it is extremely inefficient at heating water compared to tank heaters. So the more hot water you use, the better you are with a tank heater. The most obvious way to see this is to just look at the venting requirements. A tankless heater has *hot* exhaust. It is burning a whole lot of fuel (much more than the boiler/furnace that heats the entire house) and throwing a lot of that heat out of the exhaust. A modern powervent tank heater can be vented with PVC pipe because the exhaust is so cool. On efficiency the tank wins. Standby loses are the only place it loses out.
The most obvious way to see this is to just look at the venting requirements. A tankless heater has *hot* exhaust. It is burning a whole lot of fuel
I thought a tankless actually heated the water more efficiently than a tank type heater! If you're correct and all you're saving is standby loss than the primary variables would simply be the amount of insulation the tank type heater has and the difference in temperature between the water in the tank and the air temperature where the tank is located. Or do as CurlyDave suggests and put the tank heater in a place where the lost heat serves a purpose.
What about comparing a standard tank heater to a high efficiency heater. Does a "high efficiency" tank type heater just have more insulation around it to reduce heat loss or did they do something to improve the heat exchanger to make a high efficiency tank heat more efficient?
Using standard combustion efficiency they come out lower so the government came up with a new efficiency scale just for water heaters. Not sure what the units are exactly, but it's not the typical 80%, 98%, whatever that you calculate to determine furnace/boiler efficiency. That number would make the tankless heaters look really bad.
I think the high efficiency tank heaters mostly just pile on the insulation to reduce standby losses. They always seem to have a ton of insulation on them. I'm not sure if the combustion efficiency is actually any different.
I went with the tankless since I was coming from electric tank heater (sitting in the middle of the basement... with no place to vent) so I had to move the whole thing anyway. If I already had a tank heater and didn't have to relocate everything and put in a new vent, I would have gone with a straight swap just because it would have been so much easier. I think the difference is pretty marginal. The space savings is probably a better feature than the fuel savings.