tankless hot water heaters

Agreed. Also besides saving you up to 25% on energy costs ENERGY STAR gas tankless water heaters are one of the qualifying energy efficiency improvements that are eligible for a tax credit (in the U.S.) IF you make the change January 1, 2009 through December 31, 2010. If you're a U.S. resident, you should read over the tax credit info for 2009-2010 before you choose products.

Before making deal to purchase a tankless water heater, many experts recommended to always check the SEER value, Enerfy Star value, etc. It is important to know correctly how efficient the the performance................



Thank you
edited to remove link - Russ

Yes I always to check SEER value, Energy Star value, etc to know exactly how efficient performance of the unit when running......... But unfortunately it will hardly to do because some units not available for this issue...



Thank you
edited to remove link - Russ

Tankless HW tank advantages

It occurs to me that any losses eliminated in using a tankless over a tank, is limited to radiation loss from the tank itself, as well as via radiation loss via the HW piping (which should be insulated).
This means that any energy efficiency gains are limited to the seasons when no heating is required. During heating season, (for us, 7mo/yr) any HW radiation loss simply contributes to overall building heat. Keeping the HW pipe runs short is pure common sense, as is insulating the HW piping & tank itself.

The elimination of long HW pipe-runs in larger buildings is a clear advantage for tankless.

One value of tankless HW is that it is logistically easier to place a tank very close to an isolated HW tap, thus minimizing HW pipe radiation loss. But in a typical house with a single central tank located in a basement mechanical room, replacing an existing HWT with a tankless HW heater offers no gain. Perhaps another advantage is the physical smallness of a tankless HW heater, which would be advantageous in an apartment or commercial setting.

With a gas HW heater, I can understand that a short big burst of intense heat may use less overall energy than many short lower intensity burns, typical of a gas HWT.

Electric HW tanks are 100% efficient, and they are very inexpensive. Can't get much better than that. Of course not all parts of the world have cheap electricity.

Natural gas is a hydrocarbon fuel... it isn't ever going to get any cleaner, whereas grid electicity is getting cleaner all the time. But my opinion is biased... I'm an electrician.

A solar-thermal pre-heater for the HWT cold-water inlet... that's my next project

M

Electricity is such high quality energy that it is a shame to waste on heat. In the US it is often 2-4 times the cost of gas for the BTU equivalent. 100% electric heater efficiency sounds great, but not much better (5%) than high efficiency gas water heaters.