We decided against these things some years ago when we remodeled some years ago. Looking through some old threads on the subject, it seems we made the right decision.
But, we had some house guests this weekend. And the lack of hot water for baths/showers came up. We never have this issue when it is just the 2 of us.
Also, tankless water heaters didn’t qualify for Energy Star tax credits (which were available at the time we remodeled). Our current water heater is nearing the end of its life.
So would it be more energy efficient to replace it with the same size water heater, with the addition of the tankless one in the guest bathroom. Or replacing the current water heater with a larger one? Seems like heating that extra water 24/7/365 would use more energy than the few times a year we have house guests.
If you have the power available, a tankless water heater for the guest bathroom would be by far the most energy efficient solution. That said, the economics might not work out, especially if you need to pay to run 50A to the bathroom.
Plus, I did a check when I went to wash dishes, using an Instapot to measure - every time I turn on hot water and wait until the stream gets hot - it uses about a gallon of water down the drain. Since the master bath is just as far, I assume the same applies for washing hands, taking a shower or bath, etc. Maybe 10 to 20 gallons a day in this world of COVID handwashing. I guess if you live in a place where water is like gold, the instant heat would be worthwhile but in many places, not so. My municipality gets you coming and going, you also pay a sewage tax based on water use, even if it’s for watering the lawn.
You wash your hands in hot water? I can’t be arsed to take the time to stand there and warm it up, I just flip on the water tap to cold and scrub up. I only use warm/hot water to do dishes with. If it is for something that doesn’t have a fat/oil content, cold water suffices because one doesn’t need to ‘melt’ the oils. A generic tea mug is lucky to get soap … [I drink my tea with either a sprinkle of powdered lemon juice, or true lemon powder and a few drops of liquid splenda]
I don’t know how common it is, but where I am, the sewage fee is based on your average monthly use during winter. The idea being that what you use above and beyond a typical winter month is for things like filling a pool, watering the lawn and other things that don’t add more water to the sanitary system.
If you have access to natural gas or propane, whole house tankless heaters are excellent. Hot water all day long, if you want.
They are very efficient. Maintenance is not a big deal - a flush with white vinegar every year or two is sufficient unless you have very hard water.
Problem is, they are more expensive than normal tank heaters and must be installed by a pro - usually your gas company.
As mentioned above, cold water has to be pushed out of the pipes before you get hot water. The further away the outlet is, the longer you have to wait. There may be a way to use a recirculating system to get around that, but I’ve never investigated it.
Good brands are Rinnai and Rheem.
Electric whole house heaters don’t work as well as gas types, and they require a whopping big electrical service. Some of the smaller point of use heaters may require 240 volt wiring.
Something to consider would be a “mini tank” water heater like this one.
They are small enough to be considered “Point Of Use” but they only require a 120 volt outlet (on a dedicated circuit). These would be good on a kitchen or bathroom sink.
All of the electric heaters are not going to have very good flow rate.
I have one of the large Rinnai heaters running on propane for the entire house and haven’t had a lick of trouble with it for 15 years. I also have the small Bosch shown above to supply hot water to my HVAC humidifier.
Since my wife wanted one, I investigated them online. It appears that they are more expensive to install, one place said 3X, but cheaper to run and safer. However the cold water in the pipe is the big issue. Our master bath is as far from the hot water heater as you can get, and it takes forever for the water to get hot. My source said it takes longer for a tankless heater since it has to heat the water also. So, no go for us.
We’ll go back to putting a pail in the shower to catch the cold water and use it to flush the toilet.
Do the gas tankless water heaters have a variable burner? My existing gas (tanked) water heater has a simple burner on/off thermostat. The amount of heat that a tankless unit needs to generate will vary with water flow rate. If I am only using a trickle of hot water does the burner throttle down or just cycle on/off rather quickly?
Are you looking just for energy efficiency, or overall cost (including energy + capital + depreciation + water) efficiency? I don’t think you’ll get the same answer in either case.
I’d say getting a bigger tank heater would be the worst option, as it would cost more than your current size, you’d be using it every day (and it would wear out at a typical rate needing replacement), and not be as efficient at heating the small amounts of water you use 99% of the time.
The opposite end of the spectrum would be managing your guest-days hot water use so you can make do with the same-sized tank heater you already have (take on the temporary inconvenience of changing your own bath/shower time to stagger demand times for example). But I assume that won’t work.
I think rather than an expensive tankless unit which would only get used occasionally, you could figure out a way to install a cheap tank unit and only turn it on to use occasionally. A couple ideas are:
Get the mini tank heater for the guest unit to supplement what the main tank heater can put out, but have it so that you can turn it off or bypass it 360 days per year and extend it’s life and not keep 2 gallons hot all year. OR,
Replace your current tank heater with the same type and size, but keep your existing one and plumb it in series with the new one with valving that would allow you to use just the new one most of the time, but then turn on the second one and send water through 2 heaters on high-demand days. Even if your old heater can only put out half the heat of the new unit, you’d increase your heating capacity by 50% for just the cost of some plumbing parts and a couple on/off switches. AND, you’d extend the limited remaining life of your old heater if you dropped to using it 5 days a year instead of 365. DISCLAIMER: I don’t know if this second idea is legal based on your plumbing/fitting codes.
As for hand washing with cold water: most of what you’re washing off your hands is mixed into your natural skin oils; soap breaks up the oils whether they are from an outside source or your own skin. Warm water works better (try washing engine grease of under cold water), but it can be done with cold water.
Not really. I asked about that, and was told that no, it wasn’t doable (for our house).
When we moved into this house, it was apparent that there had been a burst water heater at some point that flooded the finished basement. There is no floor drain down there, and the IRS was allowing an energy tax credit that year, so we had a tankless installed. It has been working just fine for the last 12 years, requiring no maintenance to speak of. The expensive part of things was that there had to be a separate gas line run from the meter, as there is a CFM requirement for the equipment. It’s way more efficient than a tank heater that has to maintain the water temperature in the tank, and it will not wear out and flood your home like a tank heater can.
We have a Rinnai on-demand gas water heater. It’s run off bottled propane, and the heater is situated between the main bathroom and our ensuite. No real problems waiting for hot water in those locations.
It is a problem for the kitchen sink - it takes about 4 liters of water to get hot enough for washing dishes. In summer, that water goes into a bucket and on to the blueberries. I did look at getting a small thermostatically controlled electric unit for under the sink to bridge the gap, but the cost just isn’t worth it.
An alternative plan would be to relocate the tank nearer to the main bathrooms/kitchen to minimize the amount of wasted cold water. My current house the water has to travel about 30 to 40 feet.
My old house, the tank was right under the kitchen and it was a 20 foot run to the bathroom and launder room. OTOH, the guy I bought it off had 3 children and when they grew up, a basement suite that one of his married children lived in, eventually with two children. The tank was 65 gallons. When it died, I had it replaced and with only two people we opted for the cheaper 40-gal tank.
So if you are replacing the tank anyway, and running out of hot water is a not-uncommon problem, opt for a bigger tank.
Put your hand on your hot-water tank. Does it feel very warm? Whatever you feel, that’s the heat being lost to the house. If it’s not too warm, you are not spending a lot of money heating your water when it’s not being used. And if most of the time you have to heat the house anyway, it’s not a big loss. You probably lose more heat to the piping. (There are foam “jackets” to cover the pipes to lower the heat loss too. If you go to use the hot water again not long after sing it, it may still be warm).
My parents have had various tank-type water heaters over the years. Earlier, they were supplied with foam jackets to insulate the heaters but the newer ones seem to have the insulation layer built in, so I expect they would not be warm to the touch today. Similarly, I notice that the refrigerator in my apartment has much thicker doors (and therefore more insulation) than ones decades ago.
Yes.
Basically what I was saying is, if it’s not significantly warm to the touch, you are not wasting energy heating the environment instead of just the tank contents. Therefore, the only significant cost to worry about for a bigger tank is the initial purchase and installation.
(I also recall a news story about some couple who had a tankless water heater. They went off on holidays, and left their cat home for the weekend. Somehow it walked across the bathtub faucets and managed to turn on the hot water, which then ran all weekend… hot.)
We put in a tankless system in September, 2020 and the “endless” hot water is well worth it. Like others have said, first thing in the morning, you’re waiting 1.5 minutes or more of running a hot water tap before the water gets hot. Once hot, however, you never run out.
OP hasn’t said if they have gas available or only electric. That’s a major factor. I’d only consider electric as a booster for a remote bathroom that shuts off when the hot water from the “central” heater finally arrives. Some other points:
Recirculators do not get along with tankless heaters which use flow switches to turn on, but with a recirculator there’s always some flow. Maybe that can be mitigated with some creative piping. Still, t water coming back is always a little cooler than going out (hence you’re also wasting a lot of energy), so it puts a small but continuous load on the heater. My guess is it would cause short cycling as even a modulating burner’s minimum output may still be too much.
Yes most if not all tankless heaters have modulating burners because of the variable flow rate. That modulating gas valve is one of the things that makes them more expensive, same with boilers.
No tank water heater of any recent vintage (like within the last 40 years) should ever feel warm to the touch. They’re required to have integrated insulation blankets. Even so, just because it doesn’t feel warm to the touch doesn’t mean it’s well insulated. The metal casing only needs to be below body temperature to feel cool, and body temperature is easily 30ºF higher than typical ambient. Considering the large surface area of a water tank that can mean a surprising amount of heat loss. Also, gas water heaters are always losing some heat up the flue unless they have an electronic damper, and a bigger tank means more heat loss.