A tankless water heater is a copper-tube boiler with a high pressure drop and no circulator. They are manufactured for domestic water heating. http://www.gaswaterheaters.com/flash/gasheaters.htm http://www.sets-systems.com/ http://www.northdoorway.com/water/mora.htm http://www.globaltownewarehouse.com/HomeProducts/aquastar/aquastargastanklesswaterheaters.htm http://www.theplumber.com/faq.html
If your hot water use is for showers and tubs of water, and you heat your tea and small amounts in a pot, and you will have factory representatives in to completely clean and repair your instantaneous heater every year as done in Europe or Japan, the unit should suit your needs.
An instantaneous gas heater uses the same blowtorch to heat a cup of water as it does your shower water, so you will have a water heater that has a gas flame that is larger than the one used to heat your house. Most have difficulty heating less than a 1/2 gallon per minute flow rate of hot water, so they tend to waver in temperature at that slow rate, though they become steady at greater flow rates.
Otherwise they do save money by not losing heat as does a 40-gallon vessel sitting all day throwing heat away. As the gas bill for heating water for a family is about $240 per year, you could save about $60 per year, This would amortise a $1000 installation in about 16 years.
1. While the shower has its own source, what does one do about the other fixtures? Do they each have their own point-of-use heaters? Are they by supplied by a central water heater – if so, why bother with the point-of-use unit other than to have one supply tube going to it?
Unless the electricity is produced by a dam or atomic energy, the electricity is produced by burning a fuel. the line losses transmitting the electricity are high; so most electric rates are 3 times the cost of providing the heating by burning fuels in the home. Cutting the electric bill in half by making the electric usage more efficient still makes electricity more expensive.
The typical family bill for gas or oil hot water is $250 per year. The typical electric bill for the same hot water use is $800 per year. Cutting the electric bill in half still makes it $150 per year more expensive – and the cost of installation of the point-of-use electric heater is very high.
These are reasons central, fuel-fired water heaters are still preferred in the majority. Only one, long-lasting appliance required. When an instantaneous unit is used for the whole house, the small tubes lime up in many areas and a small flow from only one tap of less than 1/2 gpm makes the unit hunt. A point-of-use heater at a sink for coffee or a small sinkful does make sense, small quantities make for small bills. Showers and washers make for large bills.