The Inalienable Right– Hot Water


Whether by means of a furnace coil, electric tank, gas fired tank, tankless (see last post) heater, or other device, every American home is expected to supply enough hot water to: bathe every member of the household at least once a day to his/her satisfaction, run two loads of laundry through an automatic washer, operate the dishwasher at least one cycle, and supply hot water at each tap for the washing of hands/dishes/faces/toothbrushes.

Hot water needs run from 15 to 30 gallons per day per person, accounting for about 30% of a household’s energy consumption. Other major energy factors include heat, appliances and lighting. Few other developed countries require as much hot water per person as we do. Daily hot water usage in the UK is app. 11 gallons. The only country that uses more hot water, indeed more energy, per capita is the United Arab Emirates.

Energy is also still deceptively cheap in the USA. Most Europeans pay two to three times our cost for transportation and home convenience fuel. And we, resistant to new technologies like solar hot water, point-of-use hot water heaters, and heat-recovery of waste water, are using rather primitive equipment to heat up our precious showers.

But federal and state tax credits, depending upon where you live, can defray more than half the cost of new, more efficient equipment. The missing factor is our motivation to move forward technologically, embrace conservation until it becomes chic, and face up to the realpolitik of energy. It’s never been more cost-effective and patriotic to pursue alternative and renewable energy sources and equipment, but you do have to take the long view. The last solar hot water system I installed is calculated to pay the owners back in 10-12 years. Not many Americans are willing to wait that long to begin saving money on energy. Indeed, most of us don’t expect to be living in our present homes in ten years.

A feature of your home life that consumes 30% of your total energy budget deserves a second and then a third look. We’ll chew on this some more when next we meet. Until then, time your showers…….

It’s a Tankless Job


If I could give up the cruddy puns, I’d have more readers. As it is, the two of you are most welcome, and I salute your tolerant natures. The contraption shown at left is called a “tankless water heater.” This one is fired by propane, although we could show you electric or oil-fired models, and even a few that use wood. The idea is simple, but simple ideas are always hell for engineers. Water enters cold, leaves hot enough for American bath and kitchen use, and not much energy goes up the flue, if you believe the labels.

Compared to the electric tank that sits in my basement, the tankless heater is a marvel of efficiency. A crafty heat exchanger exposes the water to the gas flames/electric elements such that heat transfers at efficiency ratios up to 95%. My electric tank operates at closer to 85% due to various factors, mostly standby (idle) heat loss from the tank. 

The tankless heater sits cold, or barely warm, until you turn on the shower/faucet/dishwasher/laundry/jacuzzi. A flow switch alerts the unit that water is demanded, and the btus begin to flow immediately. A delay attends the operation of the heater, during which you run water, wasting a bit, and wait for the hot stuff. Usually fifteen to thirty seconds is enough. Then, as long as you continue to demand hot water continuously, the heater can produce as much as you can use, within limits.

Properly sized, the tankless heater will serve one point of use or several in your house. You calculate the capacity by the number of occupants and their habits. Teenagers count as a small village each. Old men like me are no big problem. Can I run the dishwasher while showering? Shall I operate the clothes washer and the dishwasher at the same time? There are easy formulas to help you get this right in one go.

The capacity for heating water in one pass is a thing that separates the tigers from the kittens. Electric tankless units are generally of smaller capacity, and two or more are installed in series to raise water to the desired temperature as it traverses the multiple heat exchangers. Propane or natural gas heaters are more aggressive, and usually one correctly sized heater will serve an average house. Only Republicans, to date, have been willing to accept the risks of the nuclear option, but they say the water is always hot. And wood burners can easily adjust the intensity of their heating plants by adding more logs/pellets/kindling to keep the heat exchanger cooking. The Waltons’ method, of course, was technically tankless, involving multiple pots hung over the fireplace and carried to the big washtub where a dirty Walton waited to be scalded clean.

We spent the last week at a “resort” (weathered 80 year old shacks perched on the dunes) on Cape Cod. The single modern convenience, besides a rather sluggish flush toilet (more on that topic only by request) is copious hot water supplied by propane-fired tankless heaters. Crank the shower control, wait a good half-minute, temper a bit with cold, and step in for the best shower you can get at any price. Yes, the shower’s  indoors; and it’s also outdoors— your choice. The blunt simplicity of the amenities is only meant to enhance your appreciation of the stunning views of sea, sand, birds, seals, whales (!), and well-fed tourists only capturable through wide-angle lenses. No, I won’t tell you where it is: they don’t advertise, and the waiting list stretches years in front of hopeful vacationers. Elitism has many faces.

At your house, the water heater can cost from $1 US to $3 US, depending upon the energy source and the equipment. If you’ve got a solar hot water system, you might be getting off VERY cheaply during these sunny warm days of summer. Pennies per day, just enough to run your pumps and sensors. Good for you. Next time we’ll revisit hot water and talk a bit about the more conventional optons.