One of the more popular green home products these days is the tankless water heater, which promises to reduce water and energy use.

Besides wasting water and not lasting very long, conventional hot water heaters aren’t energy efficient. They have tanks that are warmed to a preselected temperature and work to constantly maintain that temperature. One of the big problems with conventional hot water heaters is “standby loss,” which refers to the “loss of energy that results from keeping a device on standby service without actually using it,” according to Overcoming that loss of energy can result in higher gas and electric bills.

Another concern is the amount of water that goes down the drain. While you shiver and wait for hot water to make it to the showerhead, an astounding amount of water can be wasted in those three or four minutes. Typical water flows can range from five to 10 gallons per minute. In a worst-case scenario, that could mean as much as 40 or more gallons of water wasted.

These issues are solvable by installing a tankless, or “instant on,” water heater. They promise to eliminate long waits and wasted water while reducing energy bills, because they don’t experience standby loss, making them 20 percent more energy efficient. They also are likely to last 20 years, compared to 10 to 15 years for conventional water heaters.

But before you call the plumber, consider this: You can’t pull out your old water tank and slap in a new water heater without modifications involving new supply lines, gas lines, venting and electrical wiring.

In addition to these costs, prices for tankless water heaters run two to three times as much as conventional water heaters, according to Consumer Reports. Because of higher installation and purchase costs, the odds of recouping your investment before it needs to be replaced aren’t good.

Even though Consumer Reports recommends sticking with conventional water heaters because they are cheaper, there are other factors to consider. Using less energy and saving water are worth the extra dollars if you’re trying to go green.