Now, before it's an emergency, is a good time to consider the options. It's been a decade, or more, since you've had to deal with this issue and in the meantime hot water heater technology have shown efficiency improvements, especially with tankless heaters.

Rising fuel costs have given everyone an increased awareness of the energy efficiency of home appliances. This can translate into sizable savings over the life of a water heater. For a gas tank model with average residential use this could mean 60 percent ER over a 12-15 year life, for a tankless model this could be 80-85 percent over 20 years. Electric models have an even higher rating.

It's easy to see that tankless hot water heaters take the lead in energy efficiency but that is not the only factor when trying to pick the right tankless heater. Having enough capacity plays a big role as well as the cost of service from your utility provider. Figuring these is not difficult and will help you to be sure that you've made the right decision.

To make the right installation in your residence let's look at what's needed. Two numbers determine what size heater model you need. One is gallons per minute, which you can measure for yourself with a bucket and a watch to find your total need.

The second is temperature rise, which will vary by 20 plus degrees by season. To do this subtract water entry temperature from 110 F degrees (usual shower temperature) to find the Temperature Rise. A manufacturer's site will have a chart that plots these two numbers that will give you the Flow Rate of the heater you need. This will be the size heater you need.

Some residences have hot water tanks installed where there is space rather than for the most efficient use. If this problem has plagued you for too long, a residential tankless hot water heater can give you the opportunity to revisit this problem. Small, easy to mount tankless models can be placed almost anywhere there is wall space.

Multiple tankless units can also be configured to maximize efficiency. You could, for instance, have the main gas tankless in the basement and a smaller electric in the kitchen or bedroom. There are many possibilities.

A residential tankless hot water heater is probably the best way to cover you family's needs. If initial costs seem high when compared with a tank type try comparing the two over the life span of 12 years, which is how long a tank water heater is expected to last.

Also keep in mind that natural gas prices have doubled in the past decade, climbing 25 percent in 2008 alone.

A tankless hot water heater is technology that should last 20 or more.