I had used tankless water heaters before in Indonesia and in Venezuela but about 3 years ago I installed my own tankless water heater and discovered that the benefits were real.

The biggest reason I decided to go with inline water heating was because I thought it was wasteful to keep so much water constantly hot. I believed that I, as an environmentally conscious person, could do a lot better than go with a standard hot water tank. It helped that I was also in the market for a new hot water heater and that I believed I'd be saving money in the long run too.

These more efficient water heaters are known by many names. You might hear them referred to as inline water heaters, tankless water heaters or on-demand water heaters but they are all the same because they don't have a container of water to keep hot all the time.

There are two basic models of on-demand water heaters: electric or gas (Liquid Propane or Natural Gas). Depending on the intended application and installation requirements you can figure out which one will suit your needs the best.

With three people using hot water in my house I go through just THREE 20 pound propane cylinders through the winter months and less than that during the summer months. A 20 pound propane cylinder is the smaller white cylinder that you typically see on a barbecue. On average that's just 6 small cylinders of propane per year. I use and refill the small bottle because I had it handy at the time.

How to Size Your Tankless Water Heater

Sizing your tankless water heater is a really easy thing to do because if you're getting your water from the city you water line pressure will be relatively constant.

Make sure that nobody opens up any water taps while you're doing this easy test.

Grab a large pail about, one of the 19 liters (5 US gallons) will work perfectly for this – the bigger the more accurate this test will be.

Find a tap outside close to where the water line enters the house (if you can't any tap will likely be fine) and time how long it takes to fill you pail with the tap fully open.

When I did my test it took 1-1/2 minutes to fill my pail.

To find the flow rate coming from the street I just divide volume by time.

19/1.5 = 12.6 liters per minute
5/1.5 = 3.3 US gallons per minute

The number calculated will be the maximum amount of water that will ever come out of the water line unless the water provider adjusts the pressure of the line.

If you have a thermometer it would be a good time to check the temperature of your incoming water but it's not a required step.

Inline heater manufacturers tell you the efficiency of their product by giving you the specification of “Rise in Temperature versus Water Flow Rate” and you'll need this number to help you choose one that matches you flow rate needs.

It's important to remember that the number you calculated was the maximum flow rate available to you and that unless you need or want extremely hot water for your dish or clothes washer it's likely you'll never have your hot water tap wide open. Flow rate can also be reduced on most inline heaters as well so that you can find an optimal balance.

In my house I have the inline heater set to the lowest flame possible and have not adjusted the flow rate on the heater – I still have to add cold water when I shower.

Installing a Tankless Water Heater

I'm pretty good with building stuff so it took me all of an hour to install my tankless water heater. It's no harder than a regular hot water tank but you might have to make something as they are not freestanding and require a post or wall to hang on.

If you're going to get a contractor to do the installation make sure he doesn't charge you any more than a normal hot water tank installation or find a new contractor.

All in all I'm quite happy with my tankless water heater, I have to change the 2 D size batteries about once a year (they supply the power to light the flame) but have had to do no other maintenance and would recommend them to anybody in the market to replace their hot water tank.

Find a great deal on Tankless Water Heaters on Amazon.