Opinions on Hot water sources wanted

tkappeler · Nov 16, 2012

Seeing the recent thread on tankless water heaters is causing me to revisit my hot water sources for the new house to be underway soon. I have in my plans an electric hot water heater but am having buyer's remorse or something like that. The background:

No natural gas but I can use propane.
No chimney in the plan nor any place to take one out ... not at this late hour anyway so electric or high efficiency (PVC) piping is a must
Water source will be well.

Drawing energy usage comparisons between propane and electric heaters has been confusing ... it's like comparing apples to airplanes, especially when you factor in the intangibles like heat recovery times, regional price differences on electric/propane, initial costs vs operating costs, etc.

My options are:

Traditional electric hot water heater (40-50 gallon)
High efficiency gas water heater (40-50 gallon)
Tankless gas water heater (8.0 gpm or better) (with or without a small electric to avoid cold slugs through the line)
Hybrid electric heat pump water heater.

Any insight you can provide is always greatly appreciated.

BeezFun · Nov 16, 2012

I've used a few tankless systems at different camping areas and retreat centers and can't say I'm crazy about any of them. If you don't turn on the hot water with enough force, the burner cycles on and off which intermittently sends a slug of cold water. So the routine for a shower is turn on hot water full blast and temper it with the right amount of cold. I'm sure you could get used to this and it would become normal, so maybe it's worth the savings in utility cost.

My neighbor has a heat pump hot water heater hybrid, seems to work great but his house cost a couple million dollars, so I'm guessing it was not necessarily the cheapest solution. A heat pump is a pretty expensive piece of equipment and represents a maintenance expense, so I'd say it's not for joe average.

I've never had an electric hot water heater, I would think you could compare the cost of an LP fired heater with an electric without too much trouble. Electric rates are pretty cheap around here but we have natural gas so electric still doesn't make economic sense. I know LP is more than natural gas, that might swing it in favor of electric once you do the math.

Other option for an electric heater is enough solar collector to power it, probably more complexity than you want to add on a new house.

varmint · Nov 16, 2012

We've used propane fired tankless heaters for about 12 years, and you'll find (most, anyway) have remote temperature controls- up to three locations, so if you like 102 degree water temp, and your wife likes 112, no problem. We have low flow showers, and an iffy well, so we just run full hot water, at about 1 gal. a minute. It will stay the same temp., start to finish. I believe .75 gallon per minute is where they cut off, so any normal shower won't be an issue. The gas units heat faster than electric, of course. Venting is thru a side wall, either plastic of SS pipe, but none are hot enough normally to be an issue. Some use outside air, via dual wall pipe, for combustion, which might be good for your installation?

tkappeler · Nov 16, 2012

varmint said:
We've used propane fired tankless heaters for about 12 years, and you'll find (most, anyway) have remote temperature controls- up to three locations, so if you like 102 degree water temp, and your wife likes 112, no problem. We have low flow showers, and an iffy well, so we just run full hot water, at about 1 gal. a minute. It will stay the same temp., start to finish. I believe .75 gallon per minute is where they cut off, so any normal shower won't be an issue. The gas units heat faster than electric, of course. Venting is thru a side wall, either plastic of SS pipe, but none are hot enough normally to be an issue. Some use outside air, via dual wall pipe, for combustion, which might be good for your installation?

It seems like the flow sensors are better than in the past. Most I have seen are between .4 and .5 gpm to trigger the burner.

Have you had any problems with the units themselves? Would you do it again?

DKCDKC · Nov 16, 2012

Most of my hot water comes from my geothermal heat pump. In the summer all the hot water you want is essentially free - uses the heat thrown off by the AC function. In the winter the spill-over of heat from a zoned unit heats a lot of the water - so my water heater has only a minimal job. Fall and spring when there is no heating or cooling, I use a high efficiency electric water heater. Overall I have been well pleased with the geothermal unit. Had one glitch in 11 years, and it was easily fixed.

dave1949 · Nov 16, 2012

Some things to consider are: your emergency backup plan, 40 gal. tank is not big enough if you have a soaking or jet tub, is installing solar electric possible in future.

You could combine a 40 gal HW tank with a dedicated on-demand heater for a tub. An electric water heater would be feasible to run from a backup generator but propane would avoid that as long as you don't get caught with a low tank. If solar electric is a future possibility, then an elec. water heater would be most useful long-term.

It is darned hard to predict fuel prices 5-15 years in advance. There is only one fuel that you know the price of 15 years from now -- sunshine.

muddstopper · Nov 17, 2012

I think you should also consider a solar collector for heating your hot water. Lots of websites dedicated to this method. Yea, I see you are n NJ, but they use solar collectors in Alaska so!!

We can get 140 degree water in NC in Jan. Proper sizing of the collector and storage system can not only heat your water, but also your house with zero cost other than initial installation.

EddieWalker · Nov 17, 2012

I'm not sold on tankless either and have been researching what to put into the house I'm building for my parents. New technology scares me. Tankless has a lot of benifits, but mostly if you use a lot of hot water and you have natural gas available. I'm still working on getting natural gas here, so that still might be an option. They hybrid and high efficient tank water heaters are also very efficient and cost effective.

Eddie

AHNC · Nov 17, 2012

To get my disclaimer out of the way first. I represented Rinnai in the New England territory for 20 years. I am biased. That said, the equipment is excellent. There are other good brands out today as well. Your comment about the 8gpm tankless is a misunderstanding of the specs. The maximum flow thru the unit can be "up to" 8 gpm but the actual hot water output depends upon the temperature rise. A Rinnai R94 will make 4.7 gpm of water at a 70* temp rise. Generally your ground water will be in the 50-60* range in NJ. You have to decide if that is enough hot water. FYI, in a 2.5gpm shower head at 120* output and a comfortable shower temp of 108-110 (code limits thermostatic shower valves to 112*), I used 2.1 gal of hot mixing with .4 gpm of cold to arrive at my shower temp/flow. The R75/94 Rinnai units initiate flow at .4 gpm and will generally hold flow down to .25-.3 gpm. BTW, you can read all of this flow information on the touch pad(s), as well as output temp and diagnostic info.

Where people frequently go wrong with tankless is they put the water heater in the mechanical room area. That may work, but what you want to do is try to position the water heater so it is closest to the point of use. Putting the water heater at the far end of the house from where you are going to use it will just piss us both off

Locate the unit so you do not need a recirc system. Many people spend more money on the heat loss as hot water is pumped around the house than they actually do on the hot water itself. If you need recirc, the best system on the market is the Metlund Design system. If you need a recirc line with a tankless, run a dedicated 3/4" line. The Plumber will want to do 1/2". 3/4 only for the recirc!! you may find that getting the water heater out of the basement will work for you. The Rinnai uses a 3/5" concentric vent pipe. Sealed combustion direct vent. Regardless of manuf, any tankless you look at, you should compare the min flow to intiate fire and the min btu the unit can fire. As pointed out, it is the minimum flows that get you.

On a tankless water heater there are 83% units and 95% units. I just got my plans back from the architect for our bath/kitchen/etc remodel and have the choice of either. I've used tankless for 14 years and I am going to go with the 83% unit. For me, the extra few hundred dollars cost of the condensing model is simply not worth it. For years I've used 10-13 therms a month for dhw. The condensing unit would knock that down to 8.5-11 therms. For me, I will take the simplicity and lower cost of the 83%. The reason to go with the condensing model is if you need the higher hot water output. The 4.7 gpm of the R94 would be approx 5.8 with the RU98 condensing model.

You need to look at your fixture load and use. YOu don't say how you are heating/cooling the house so I assume you are going warm air. A good option to the tankless is to go with a Condensing Wall Hung boiler and an indirect water heater. Rinnai has just introduced a package boiler water heater that is the balls. You could then use the boiler to drive a series of SMALL air handlers. That is the best way to zone a ducted system, imho.
I will never install a piece of ductwork again as I've made the switch to mini-split heat pumps and am enjoying the savings and comfort. I also represented Fujitsu in my business, but that is another topic. you might want to look at Fujitsu's Hybrid Flex Inverter system.

It pains me to say this, but solar dhw just does not work out number wise any more. I was in the solar business back in the 70's-80's and did hundreds of dhw systems. Today, if you are going to do anything solar it should be pv, again imho.

#1 Selling Gas Appliance Manufacturer Rinnai voted "Best Tankless Water Heater" | Rinnai America
fujitsugeneralamerica.com

muddstopper · Nov 17, 2012

AHNC said:
It pains me to say this, but solar dhw just does not work out number wise any more. I was in the solar business back in the 70's-80's and did hundreds of dhw systems. Today, if you are going to do anything solar it should be pv, again imho.

QUOTE]

I am not up on the meanings of dhw or pv solar so maybe I am thinking about something entirely different than the systems you are refering to. What I do know is that for about $100 in copperpipe, aluminum flashing, some plastic glass and a old hot water heater salvaged from the local dump will net me almost my entire year round hot water supply for showers, bath, washing and cooking. I cant figure out how any other water heating devise being sold on the market can post out better working numbers than that. I can enlarge this same system tieing it into a radiant floor heating system and pretty much heat my entire house. If Rinnai, or any other manufacturer of electrical or gas hot water heating systems can beat the numbers of a properly designed solar water heating system in terms of initial cost and future associated cost of operating their systems for 5-10 or 20 years down the road, I sure would like to see their numbers.