It seems like there's still no clear winner on the tank vs. tankless debate. While I've lived with my tankless for 2.5 years now, love it and am a strong advocate from a convenience perspective, the questions regarding cost effectiveness, newer and more efficient tank options, and electric vs. gas persist.
According to the U.S. Department of Energy (via Finehomebuilding.com), water heaters consume 14% to 25% of a home’s annual energy use so ensuring yours is efficient should be of high priority.
FineHomeBuilding.com has a fairly comprehensive article outlining the pros and cons of tanks vs. tankless among some of the more popular manufacturers. They also cover a broad range of issues including proper sizing, efficiency, and an overview of how they work.
Below, are the pros and cons of each tank and tankless water heater (via FineHomebuilding.com). See the full article for more information:
Tank
Pros:
- 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
Cons:
- Standby heat loss
- Can run out of hot water
- Tanks are large and heavy
- Higher life-cycle costs
- Temperature control might not be precise
Tankless
Pros:
- 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
Cons:
- 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
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In my mind there is one huge plus for a tankless water heater, and that is you don't have to run the tap for minutes wasting water waiting for hot water from the water heater. We used to keep old milk jugs and fill them with the cold while we waited for the hot water to get there. Now our hot water arrives within seconds, and its HOT right off the bat. All other arguments are moot in my mind, Tankless all the way!
Of course, that relies on distance from heating source to where you want the water, right? If I had a tankless in the same location as the tanked heater wouldn't I get the same few seconds of cold water that has been idling in my water pipes?
We have a tank water heater. My thoughts is why isn't there a timer for it so that during periodic non-usage like in the middle of the night, it can be automatically set to a lower temperature. May be the energy used to bring up a cooled down water is higher than just maintaining the same water at high temp? does anyone know?
I think you are on the money with that one.
I don't like the tankless water heaters. They require more maintenance. They won't heat a small amount of water (useful for shaving) and they won't heat if your water pressure drops (issue with well pumps before the pump kicks in).
Some other options aside for the tank that most people think of are:
Electric heat pump tanks entered the market last year and are suppose to easily replace a electric tank. If warm climates they are extremely efficient. I'm not sure how well they do in cold climates. They work like a regular electric heater if there isn't enough warm air around them.
There are also gas condensing tank water heaters coming out the middle of this year. They are suppose to be about as efficient as gas tankless. I read a claim somewhere that they heat the water up quickly.
And of course there are solar water heaters. I've only heard wonderful things about them although I'm sure they have their issues.
There is more information on all of them on Energy Star's site.
I've had a tankless water heater for a year now, and I love it. The hot water does take a bit longer to get to the tap than with the tank heater, but it's nice to have an unlimited supply. My gas bill is also a bit lower. My main reason for splurging on the tankless though had to do with space. I live in 720 sf house, and that 20 cubic feet or so is really nice to have.
Souk --- That's a great idea, but you would not want to cool them very far. Below 120ºF and you seriously risk growing Legionnaires' bacteria in the tank. So if set yours to the 120º-130º range normally, you're already at the safe minimum.
bagelpower, that only works if the tankless is in the same room as the tap for hot water. In the US, most tankless water heaters are placed in the same location as the original tank water heater, so you still have to wait for the hot water to get to you but once it gets to you you have unlimited hot water.
Great topic! We had to replace our hot water heater last week as our old one was leaking & a full scale disaster was just avoided.
My husband did a load of research in the 2 days before we called the plumber (we emptied the tank & went w/out hot water those very long, cold 2 days). Since we live in an 80 year old home, we were limited by our options. I would have loved solar HW, but our trees block our roof from the sun for 75% of the day. The previous HW tank was gas fired. Putting in one of the new, more efficient electric models would have required us to call our electrician to put in a special outlet. And it still would not be as efficient as the newer gas models. Putting in a tankless model would have cost so much more money- literally several thousand. Here's why- we would need a 5" stainless steel flue dropped down our chimney. That would be about $1000 (and there's no one that would put that in Mass. during January with slippery snow on the roof). Then we'd have to have a larger gas line put in. Plumbers don't do that cheaply either. The cost savings in reduced energy usage were not great enough to offset the increased installation price. We were looking at a 20 year payback timeframe & that was just not worth it to us. Sure, we know gas prices will rise over time. Since we installed (or had installed, I should say!) the most efficient HW heater we could, we are still doing better, by at least 10%, than we were just 2 weeks ago
Souk, when I lived in France my tank water heater was on a special breaker that included a timer. The water was heated during the night, when electricity was cheaper, and just stayed hot during the day thanks to good insulation of the tank. There was a special position of the switch to force the heater on during daytime and I used that occasionally, when coming back from a trip, to heat my water for a shower (I was turning off the water heater before each trip).
All modern apartments in France have that feature.
@bagelpower: "Now our hot water arrives within seconds, and its HOT right off the bat." Interesting. I wonder if this depends on your tankless model and placement? I have friends who have tankless and they report the opposite - when they had a hot water heater, hot water would arrive quickly, as it would just have to flush the cold water out of the pipes. Since they moved to tankless, they find it takes a while for hot water to start flowing, because not only does the old water need to be flushed out of the pipe, but the tankless heater needs to heat up to the point where it's heating the water. This is one tankless heater that feeds the whole house, mind you - not one of those heaters that attaches at the faucet.
ddk, so are you saying when I go on vacation, I shouldn't turn my water heater way down? There is a vacation setting on my heater. Would that lead to bacteria infested water? Yikes!
I just had to have the tankless heater in my classroom replaced today (with a small tank). I asked the plumber what he thought about the tankless, and he said they are a waste with our very hard water. Most only last a few years here according to him. Doesn’t seem worth the additional cost.
RedCat - thanks for mentioning the electric heat pump option, I hadn't heard about it before. Has anyone tried it yet? It looks like they could be difficult to find since they are so new.
What no one has commented on yet is that tankless water heaters require a minimum water pressure. This means if you get a tankless and put a low flow showerhead in your shower, you are going to be taking cold showers.
Vanessa W - we have both a tankless water heater and a low-flow showerhead and we don't have any problems with the temperature. Maybe it depends on the model, but ours puts out heat for anything more than a very small trickle of water.
The only cons I can really identify are that it takes longer for water to heat up, as some have mentioned, and it's a bit noisier than a tank. But our heating bill dropped by quite a bit right after we installed it and the additional floor space is very welcome.