Tankless Water Heaters. Home Depot article.

I have had many discussions with people and contractors about this type of unit. They do not work in larger homes, and the use of water goes up in most cases by double. You may save on gas, but with the higher water usage to make the units heat, money savings is about zero.

Many larger homes will need two units, and that means two gas lines, and two meters. I had a friend who wanted tank-less in his 4,000 sq. ft. 4 bath home. He changed his mind quickly, when the costs was going to be five figures. When you figure the formulas, number of faucets, showers, bath tubs, wash machine, dishwasher, etc. he found out he actually needed three units. Not cost effective.

I suggest to my clients who hear about tank-less units to do google searches and learn about the formulas and costs of installations of these units. It may take many years to reap any cost savings. They are popular in other countries who have small homes and apartments, and they do save space. Be aware of trying to use these units in larger homes.

Are Tankless Water Heaters a Waste of Money?
The energy savings you’ll get from a tankless water heaterare usually too low to justify the high purchase price
Posted on Apr 6 2012 by Martin Holladay, GBA Advisor

Will you save enough energy by installing a tankless waterheater to justify the high cost of the equipment? According to Minnesotaresearchers, the answer is: probably not.
Although tankless water heaters are, on average, moreefficient than traditional tank-style water heaters, they’re alsomore expensive — so expensive, in fact, that many potential customers wonderwhether their high cost can ever be justified by likely energy savings.
Before you can decide whether tobuy a tankless water heater, you’ll need to know how much energyyou’ll save. Can you trust the information provided by tankless water heatermanufacturers — for example, the estimate from Rinnai’s online calculator thatyou’ll save $178 per year?
Before I get around to answering that question in detail,suffice it to say: probably not.
Real-world answers from a monitoring study
To figure out the payback period for the incremental cost ofa tankless water heater, it would be useful to know:
The installed cost of a tankless water heater;
The number of gallons of hot water used per day by theaverage American family;
The in-use efficiency of a typical tank-type water heaterand the in-use efficiency of a typical tankless water heater;
The annual natural gas savings and the annual dollar savingsattributable to switching from a tank-type to a tankless water heater.

The biggest expense is usually the gas meter and gas line upgrades. If the normal gas meter is installed and there are other gas appliances, chances are the meter won’t meet capacity and neither do the gas lines. Waste of money and water for little benefit.

Saw this setup of six units and two storage tanks with circulating line supplying hot water to all units in an eight story condo building earlier this week. Seemed to work well.


Here’s a typical set up I see in my area. This was a large unit with several zones which worked well. Granted some water is wasted when waiting for hot water at the fixture’s.

The last picture is of a boiler I’m installing in the house I’m building. I chose an 85% efficient boiler because it’s half the price and since it’s a second home I don’t really care about fuel efficiency. It’s a combo boiler for domestic hot water and baseboard heat.

Griffeth 044 (Small).JPG

Put a motion sensor in each bathroom that turns on the recirc pump. When someone walks in to use the facilities, the pump starts and by the time they are done with their business or get undressed to use the shower, the water to the faucet is hot. See a lot of those in upscale homes with some distance to the tank. Oops. Upscale homes. I forgot you were a home inspector. Never mind… :wink: