Tankless water heater and front load washers
by Jeff
(Southern California)
My home has a natural gas tankless water, but I recently purchased a new High Efficiency front load washer and have a question. I am not sure my new washer is getting hot water due to the short duration of the water fills. The valve only opens for a few seconds at a time during the fill cycle and my tankless requires at least a few seconds before it will even begin heating water.
If my assumption is correct, is there a solution to this problem? Possibly a Point of Use water heater? It is frustrating that the two energy efficient devices don't get along better and that I might have to add another energy consuming device to fix problem. Any advice would be greatly appreciated.
Answer from Green Energy Efficient Homes
You raise an interesting question that hadn't occurred to me - for two reasons. First, I don't own a tankless water heater because I have had so many people tell me about their bad experiences with them (and I had a bad experience with one when I lived abroad in Costa Rica for a year in 2008-09). Problems have included reliability, frequency of breakdowns, cost of repairs, inability to use short bursts of water (such as in your situation or when washing dishes for example) and inability to run the water at lower rates of flow because the heater doesn't engage. Most of these problems have occurred in North America. I lived in France for four years in the 1970's and had a tankless water heater there that worked wonderfully, and my sister lived in France for a few months last year and had no problems with the tankless water heater in her home there.
Second, I never wash laundry in hot or warm water. I find cold water does a perfectly good job, and bear in mind that the heat in the water is the biggest energy use of a washer, HE front loading or low efficiency top loading.
My sister and her husband have the exact setup you describe - tankless water heater and front load washer - and for years they washed diapers in the washer (they have four kids after all!) but they used cold water precisely because they found the water never really got hot in the washer anyhow, and cold water did a fine job.
One way to work around this problem is to start your load of laundry and immediately start using hot water somewhere else (for something you would have done anyhow). For example, plan to take a shower at the same time you start a laundry load. A low flow showerhead is often not enough of a draw on a tankless water heater to get the heat going on its own; combining this with the fill cycle for a front loading washer and you might have the right amount of draw that both your shower water and the laundry water are warm. You could wash dishes instead, as another alternative. Or you could just turn the tap on at a trickle - enough to keep the heater on - so that when the washer draws water from the hot water pipes, the heater is already running. Unfortunately these ideas all create waste, which is another reason I am not all that fond of tankless water heaters: I find that some of the savings of a tankless water heater get eaten up by compromises in the way you use hot water. For example, I can wash a complete load of dishes by hand at my house with about 2 gallons of hot water. At my sister's house, where I was doing the dishes last night for a big Mother's Day family get-together, I wound up using twice as much water because I wanted some hot water to wash and some warm water to rinse - and in the end the water in the sink was only lukewarm at best.
I would probably wash in cold - like my sister, I haven't used anything but cold water wash for years, and everything seems to come out clean.
The only other suggestion I can make - in answer to your question of whether you actually are getting hot water in there - is to pull open the detergent dispenser partway through the fill cycle to see whether the water has heated the dispenser. The temperature of the plastic around the dispenser should be somewhat changed by the temperature of the water flowing through it. Or you could feel the glass on the door - it should heat up if the water inside is hot.
A point of use water heater may be a viable solution if you really do need hot water for your washing machine, but these often have limited capacity - they are actual tank water heaters, not tankless. For example you can buy a 2.5 gallon point of use water heater which is probably enough for one load of laundry. The nice thing about this approach is that you can put the heater on a switch and only turn it on an hour or so before you're ready to do laundry. The bad thing about this approach is that, if you leave it on all the time, you'll be keeping that 2.5 gallons hot continuously when you might only be doing a load of laundry every few days.
I suspect you can see my bias here: when I look at all the compromises you have to make to use a tankless water heater, I begin to suspect it isn't saving that much energy for a lot of people - especially now that there are ENERGY STAR water heaters such as condensing gas heaters that have almost the same efficiency as a tankless water heater, and provide a tank of hot water so you always have enough whenever you need it.
Sorry I couldn't provide a real solution to your problem, but thanks for your question and the points you raise, and feel free to post your own thoughts on my suggestions - as well as any solution you come up with over time.
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