propane $2.35 electricity 12 cents

14 years ago

Looking at tankless vice electric and now electric HPWH. I was recommended for my house size 2 Rinnai 9800 series. That is over $4,000. With propane at $2.35 and a small family 3 within a year going to 2. I am now thinking two electric water heaters to support my needs vice propane tankless. I am splitting support for each side of the house main level and lower levels. One to support 3 full baths (and steam shower) the other to support 1 full bath laundry, kitchen and two laundry sinks (garage and mud room) and summer kitchen downstairs. Only one kitchen would be used at a time. Or run just cold line to the main kitchen laundry, mud room garage and do a flash heater to support just those. We don't laundry with hot water very often and unless we are cleaning stuff the laundry sinks will not use hot water often either. We do dish washing every day though. We are installing a heat pump and now I am interested in the aspects of using it as a source for heat for my residential water heaters. We are still leaning on dual fuel HP because out in the country we lose power more than built up areas but again with the cost difference in fuel may go straight electric. That is what we have now for a 1200sq ft place. New house 4500 sq ft. Comments

Sort by:Oldest

Comments (4)

jake2007
14 years ago
last modified: 9 years ago
The tankless heater is about 82% effecient while the electric tank is close enough to 100% that we will call it that.

For the amount of water heated by 1 gal of propane in a tankless heater it would cost you $2.75 for electricity. Propane is cheaper - right now.

I'm not sure it makes sense to switch to propane and a single tankless - let alone two. I think propane is much more volatile price wise than electricity - but who knows going forward.

I think a point of use electric heater can be appropriate for the limited uses that you are describing. Don't consider it for whole house.

I don't know anything about HP recovery - but I would encourage dual fuel so that you aren't over a barrel. Plan for much higher fuel costs and build-in efficiency and insulation.

I can't imagine going to a 4500 sq ft house 4 full baths and two kitchens at the same time a small family is getting smaller (from 3 to 2).
sniffdog
14 years ago
last modified: 9 years ago
lisa

you might want to get some additional quotes on the Rinnai's - that price seems a bit high. I have a dual tankless Rinnai system. I don't know the exact price I paid just that the delta cost was an additional $1200 above what a large single propane water tank option would have cost. ANd there is a tax credit if you put one in - I think we got $250 but the tax credits have gotten better.

The key point on the tankless decision for a family is that you won't run out of hot water (unless you forget to fill the propane tank up) which if you read on the forums is quite common with families. Kids seem to always drain the tanks and the recovery time is hours. With tankless you can run them until you run out of propane.

We put in the tankless units mainly because it is just my wife and I and we don't need a lot of water unless we have guests. The delta upgrade cost was relatively low and we got a tax credit - so it seemed to make sense. The way ours works is that only one takless unit fires up if the demand is below 4.5 gallons per minute. ABove that - which is rare - the second unit fires up. I really like that feature.

The one thing you must understand about tankless is that the way you use the system will have a great impact on the cost to operate it. Everytime you turn on the hot water tap - the gas units fire up. There is a realtively short time for the tanless units to get the water hot and then you have to wait for the hot water to push cold (or warm) water out of the hot water line pipe unitl the hot water reaches the tap. So you really don't want to short cycle the tankless system by turning hot water on/off rapidly. I think you must consider the placement of these units very carefully to make sure you don't have to run the taps for minutes to get hot water out. But that is one advantage of the tankless units - you could put multiple units close to the point of use. Tanked system have the same issue with water delays but you won't short cycle them is you turn the tap on and off - and you don't have the same flexibility for locating the tank as toy do with the tankless.

I found the need to install a small hot water recirculating system to service our kitchen, utility room, and butler pantry sinks because the Rinnai's are located 88 feet away from these sinks and that was taking 5 minutes to get hot water at those taps. We placed the Rinnai units in the basement directly below the master suite so we get near instant hot water at those taps. We could not locate Rinnai's on the other end of the house due to venting restrictions which is also something you will need to work out.

I would have prefered to have 1 Rinnai service the master suite, 1 Rinnai service the kitchen/UR/BP sinks , and 1 Rinnai to service the second floor guest bedrooms. That would have been the ideal solution for us but we could not do it that way.

We live in a rural area too and so there is an extra benefit for either a gas tankless - or gas tank - and that is you can easily backup the hot water system with a reasonably sized generator. If you can't do better on the price of the Rinnai's, I suggest going for a propane tank system and spend the money on a backup generator which will come in handy in the sticks.

The dual fuel option on the heat pump is a great idea. I have Geothermal heat - so when we lose power I lose heat. Our Auxiliary heat is electric - the dual fuel option wasn't presented to us as an option. Our solution was to install really good wood burning & gas fireplace inserts that are rated as heaters (we have 3 on the main floor - 1 wood, 2 gas). These units need a little electricity to run the fans and controls - and I have those on my backup generator. If I could do it all over again I would have gone dual fuel on the GT system with propane as the Auxiliary source.

I have seen lots of calculations for and against tankless. In the end maybe they save us a little money but that wasn't the reason we selected them.

I can't stress enough to think out the entire hot water flow thing before you plumb. It is very easy to calculate for a given diameter and length of hot water feeder pipe how many gallon sof water are in the pipe. Then realize that a tap on full might run at 1.5 gallons per minute and then you can figure out the delays. It was a huge issue for use which I had to fix after the fact just before we moved in because DW hated waiting for hot water.

Good luck with your build.
Related Discussions
HeatPump,to use hybrid/propane or electric strips
Q
Comments (5)
Yes, the heat pump is generally sized for cooling. I have heard of some installations where they size them for heating, but am not personally familiar with this. I think this is generally more needed in a climate colder than yours, but it would be worth asking your installer about. What's the installation cost difference between the electric backup and gas backup systems? I'd think it would be at least a couple thousand dollars. So right there, to me anyway, is a big factor in the decision. With the numbers you're looking at, I can't see where gas backup would save you anything, but even if it saved you a couple hundred bucks a year, that's a long payback time. One other thing, too, is controlling those gas backup systems for optimum performance can be tricky. A friend put one in his house (which had an existing propane furnace) and it was factory set to change over I believe at 35 degrees. He lowered it, I forget to what, but he had to play with it quite a bit to get it to a point where it seemed optimum. With the all-electric, the strips will come on to help the heat pump when needed, but you still get the contribution of far more efficient heat from the heat pump, whereas he loses that on gas backup. In his situation, it was good, because he already had the propane furnace and did the heat pump when he needed to replace the a/c anyhow, but I think for you all-electric would make more sense.
...See More
electric baseboard vs. inefficient propane
Q
Comments (16)
Does the piping have an air elimination valve? This would be near the boiler somewhere, usually between the boiler output and the circulator. The circulator should be at the boiler output pumping the water away from the boiler. The circulator should not be at the return end of the system. Th position of the circulator in the system is important for eliminating air pockets. Is there insulation below the concrete slab? The type of system you have, called a high-mass system, should not be run in a manner which varies the temperature inside the house. Also, high mass radiant should have an outdoor reset controller, to more efficiently react to weather changes. The boiler should have a by-pass loop, which will allow the boiler to run above 140 degrees, preventing condensation. Alternatively, you should have a condensing boiler, which is corrosion resistant and runs at lower temperatures. Can you describe the type of in-slab piping that you have? Length of run? diameter of pipe? Spacing between loops? Electric baseboard heaters are 100% efficient, no matter what kind you get. Heating a house with electricity doesn't seem like something you coulod do with solar cells, as you would need a lot of panels to generate the amount electricity you wuold need..
...See More
electric vs oil hot water
Q
Comments (5)
I live in the North East. I have a new oil fired boiler (1 year old), forced hot water system. It has 4 zones, one of which is for my domestic hot water tank. The boiler will only fire if the aquastat is below setpoint and there is a call from any zone, so it does not run to maintain a boiler setpoint (which is good). With the price of home heating oil averaging $4.75 a gallon, I am taking some steps to cut back on costs. One of which has been the recent purchase of a Pellet stove. I plan on this being my primary means of heating my house. I am questioning whether or not to install an electric hot water tank as my primary source of domestic hot water instead of my indirect domestic hot water tank. I have asked around, both via associates in the trade and reading the online forums. Pretty much everyone seems to believe electric hot water is cheaper. I want to believe that is true, but my calculations tell me other wise. I could be overlooking something, I sure hope so. Anyway, please review the following and advice. Thanks Home heating oil produces about 140,000 BTU per Gal My boiler is 84% efficient, which yields me 117,000 BTU per Gal. Heat losses due to piping etc I cant calculate, so I will stretch a guess and say 10% heat losses. So now I yield 105,850 BTU per gallon. Circulator pump and Burner motor running consume 2.41 amps combined, consuming .2892 KWH @ $.18415071 per kwh = $.05 an hour to run. (is that right?) So to get the 105,850 BTUH from a gal of oil it costs me $4.75 + $.05 for pump and burner run time for a total of $4.80 Now to get the same 105,850 BTU from an electric hot water tank, and figuring electric heat at 100% efficiency ( I realize its probably more like 97% in reality). 1 KW = 3,413 BTU. So 105,850 BTU divided by 3,413 BTU = 31.01 KW needed to produce the 105,850 BTUÂs So 31.01 KW times the cost of $.18415071 per kwh = $5.71. My calculations here tell me to get 105,850 BTUH from my oil burner cost me $4.80 My calculations here tell me to get 105,850 BTUH from Electric hot water tank cost me $5.71. What am I doing wrong here? Thanks
...See More
is Tankless really better than electric std water heater
Q
Comments (17)
city Agree that there is something not right about the kitchen and laundry room. I would have the plumber check if there are anti-scalding valves on the fixtures. When we first moved in, I had to adjust these to properly work with the tankless units. The problem was that out of the box, the fixtures were set with too much cold water in the mixture, and it took forever for the hot water to overcome the cold water mix. At 15 to 20 feet away, the delay should be less than 10 to 15 seconds or so. The master bedroom is another story. I would check anti scalding valves in the master bath and adjusting those might help a little. But you still have 70 feet of water to push out of the way. There are other solutions besides the water recirculating system: - use small point of use hot water generators underneath each master bathroom sink. If your main issue is getting hot water to the sinks (and you don't mind waiting a little for the tub or shower) then the point of use systems can fix that. They make several types - both tank and tankless. The downside is that you need to run seperate power to those units, but it might be a lower cost option in the long run (see my note below on recirc loops). I have one of these under my butler pantry for generating hor water for tea and it cost 140 dollars for the unit. - If you have 2 Rinnai units, perhaps move one of them to the side of the house where the master suite is. The closer you get the hot water source to the master suite, the faster you will get water. This may not be possible since venting the unit if it is gas can be a challenge. - Add a small high efficiency hot water tank on the master suite side of the house to fee the sinks and shower (let the tub remain fed by the tankless). You can get a small tank sized for your daily sink and shower needs. Then you have the recirculating system option which requires a small tank (4 to 10 gallon electric or gas tank), a small pump, and all lines in the recirculating loop to be insulated. The small tank must be sized properly - not just the amount of gallons it holds but the heating element size - or the system might not work properly. You also have to realize that your monthly energy costs will go up because you must keep the pump running during the times when you need hot water. The cost to run the pump is relatively low - pennies per day - but the cost to keep heating the water as it cools when looping can be significant. If you do go down the recirc loop route, get a pump that has a 2 timers on it. Then you can set the timers for morning and evening use, but turn the pump off when hot water use is not expected. The tank remains enegergized all the time - and turns on based on a thermostat - to keep the water at the set temp but since the water is not looping when the timers are off, the amount of energy required to keep the hot water in the tank hot is minimized. I would find a good plumber who can give you an independent evaluation for solving your issues. It sounds like the builder just wants you to throw money at the problem and that might not be the best way to handle it.
...See More
sunnyflies
14 years ago
last modified: 9 years ago
I am about to put in a Geothermal system and I am interested in why you would go with propane as a back up vs the electric strip.
sunnyflies
14 years ago
last modified: 9 years ago
I am about to put in a Geothermal system and I am interested in why you would go with propane as a back up vs the electric strip.

propane $2.35 electricity 12 cents

Comments (4)

jake2007

sniffdog

Related Discussions

sunnyflies

sunnyflies

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US