The Tankless water heater debate rages on.

So we’ve repaired our current water heater more than once, and we know that it’s probably going to finally give up the ghost any day now. We’ve been putting off replacing it as long as possible because we haven’t been able to decide which kind we want to replace it with.
Tankless water heaters appeal to me for many reasons, not the least of which being the size. With just a tankless, we could reclaim a huge chunk of a closet that’s currently filled to capacity with the old standard model. Then there’s also the potential energy savings from not keeping water hot when we don’t need it.
Unfortunately, that’s not where the decision making ends. First, we currently have a gas water heater, and looking at varying sources about efficiency, a gas tankless seems to have much lower efficiency ratings than an electric model. We’d also have to run larger gas lines under our house. Switching to electric would require running new 220 line, and would eliminate one of the things I love about our current heater: that it can still heat up when the power goes out. There is also some debate over whether or not we’d really see much in the way of energy savings, since there are only two of us, our new dishwasher heats it’s own water, and we do most of our laundry on the cold setting.

Fine Homebuilding has a nice article on their website going through the pros and cons of each type of heater.
(You can download a PDF of the article HERE.)

For the common tank style heaters, here are the pros and cons:
• Lowest up-front costs
• Easiest installation and replacement
• Some models don’t require electricity to operate
• Uses a wide variety of available fuels
• Can be located anywhere in a home
• Works well with recirculating systems

• Standby heat loss
• Can run out of hot water
• Tanks are large and heavy
• Higher life-cycle costs
• Temperature control might not be precise

For Tank-less heaters, there’s an equally long list of good and bad:
• Lower life-cycle costs
• Endless hot water
• Runs only when needed, offering the potential to save energy
• Accurate temperature control
• Small and spacesaving; typically wall-hung

• Higher up-front costs
• Complicated installation; larger fuel lines often required
• Electricity required for most models to operate
• Untreated water can lead to scaling and reduce or halt flow
• Can suffer freeze damage if improperly installed
• Minimum hot-water flow required
• Recirculation is more difficult, with potential to compromise warranty

Of course there is another system option that we’ve considered – Solar.

Solar only works with an existing tank system, but it promises to lengthen the life of that system, as well as drastically reducing it’s operating costs. Estimates put the savings at an average of 50%.
There are options ranging from everything-you-need-in-one-box kits to instructions on building and assembling your own system. Over on Instructables, they’ve even got a handy tutorial on how to DIY this for around 5$. (WOW)

Given this option to add solar to a tank system, that might tip the scales in that direction for us. We’ll see. Either way, I’ll be sure to update when the time comes.
Have you made the switch to tankless or solar? Any words of wisdom? I’d love to hear some real-life feedback!


11 thoughts on “The Tankless water heater debate rages on.

  1. One thing to consider on the tank system — if you buy a new high efficiency (12 yr warranty or possibly 9 yr; note that the higher lifetime ones are also the highest efficiency ones, as I believe FBH covers) gas water heater it may not be able to heat when you have no power. One of the ways to improve efficiency is to replace the always on pilot light with an electric ignition, so you only burn gas when you must. You may want to check that if you look at a gas tank system.

    Another resource you may want to look at for ideas is . They’ve got a lot of good research on energy efficient solutions.

    PS — I’m the husband of Heathrow from LJ.

  2. Thank you for that! One of our other friends installed a tankless, and he’s mentioned some things I’m not sure I could get used to, as well as a few installation headaches he had to deal with.
    All of this is SO good to know ahead of time.

  3. We just recently replaced our tank-style water heater with a tankless. We did have to run some new gas pipe but it was pretty painless. It’s too soon to tell if there will be significant energy savings but one other thing that made the tankless heater attractive is that there is a rebate program from both our energy company and through the federal government (,,id=206869,00.html) through 2010.

      • I did have a certified installer because we were having them work on our hydronic heating system as first priority. The tankless heater was something we’d been considering and since everything else that came with the house was breaking down we figured it was better to replace the old water heater now than have to revisit the whole thing again in a year.

        Our tankless does dual duty. It heats water for our hydronic heating, running a closed system of 3 gallons or so of water through the heating system (and a heat exchanger). It also heats our potable water (which used to be part of the same system before we closed off the heating system unto itself). Prior to the redo we had to have the water heater turned up to maximum in order to get any heat in the parts of the house furthest from the water heater. Since the redo we haven’t had to do more than circulate the water, haven’t had to turn on the blowers to force warm air into any room in the house… so in that sense, I’m VERY pleased with the new system.

        One difference is that a certain amount of water needs to be drawing through the tankless heater to trigger it to turn on. We can hear the hum of the pump when it turns on and hot water follows shortly thereafter. EXCEPT where we had installed low-flow nozzles. My understanding is that the low flow doesn’t have enough “pull” to trigger the heater, so I have to turn the kitchen faucet to completely hot and let it run for a while before the hot water kicks on. The two technologies don’t seem to want to work well together.

        Other than that, I’ve been very pleased with response time and haven’t noticed any weird cold spells in the shower. It’s nice that I can run the dishwasher, do a load of laundry, and hop in the shower all at the same time (getting all my chores done at once before I start my work day) without worrying about the dishes not getting clean in a lukewarm wash. And for the improvement to our hydronic heating system? Unreserved THUMBS UP.

  4. I don’t know many of the details, but my parents have a tankless system and though my dad is usually a pretty good DIY-er, it has been regularly broken in one way or another. I think what’s going on now is related to the hard-water scaling you mentioned up there. And I don’t know if this is tankless-related for sure, but it takes FOR EV ER to get the hot water to the places in the house that are furthest from the system. Since it’s set up in my parents’ bathroom and hot showers are all my dad needs (not washing dishes or anything ofc!), he doesn’t see this as a problem though.

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