Installing On-Demand Water Heaters

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Installing On-Demand Water Heaters Compact tankless water heaters free up valuable space and save energy, but sizing and installation require a unique approach David Grubb In recent years, about half of my remodeling customers have chosen to replace their conventional water heaters with on-demand — or "tankless" — models. Long popular in Europe and Japan, on-demand water heaters first showed up here during the 1970s energy crisis. Their use never became widespread, however, because energy prices fell and early models had reliability problems that made plumbers suspicious of this technology. Today's fully electronic models are very reliable, and with energy

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4 Comments so far...

• I was wondering how David came up with the .41045 number he used to determine operating costs ? What does it represent ? And how could I use it on other gas consuming appliance ?

  Posted by: AJ Stones on February 13th 2006

• On p. 4 - Adding 120 amps to your service panel isn't cheap. On. p5 (bigger gas lines)- 3/4 inch gas lines won't always suffice. Need to check piping charts. On p. 7 (cost to operate): While the yellow Energy Guide label may have an outdated gas cost, it does list estimated therms at 64 gal. of hot water per day. Most households in Wis. use less than 64 gal./day. On p.8 (Energy Factor) Some demand water heaters still have pilot lights, in which case their Energy Factor is listed as around .67. Correct the math-a water heater with an Energy factor of .82 is about 28% more efficient than one at .59EF, not 40% more efficient.

  Posted by: Jonathan Beers on February 16th 2006

• Great article, good to see someone candid about the cold water 'slugs.' I like the technology, personally. Math? A water heater with an energy factor of .82 is about 40% more efficient than one at .59EF, and the one at .59 is 28% less efficient than the one at .82EF. It's like buying something on sale -- if it's marked down 20%, the original price was 25% higher than what it's selling for.

  Posted by: George on February 18th 2006

• Nice to see info on the tankless wh. They have an endless supply of hot water, but will they work in a hot water recirculating system without loosing efficency?

  Posted by: Andre Ballowe on March 1st 2006

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