It is without doubt that tankless gas water heaters are very energy efficient. Although there are times these models are unsuitable due to certain situations, if they can be used they offer significant amount of savings on utility bills. This is mostly because water is heated only when it is required, thereby saving substantial amount of energy as compared to conventional tank versions that always heat water to maintain it at a certain temperature.
Even if it can be said that tankless gas water heaters are very efficient type of water heating system, it cannot be said that they do not have any disadvantages towards their tank counterpart. The truth is tankless gas water heaters have their advantages as well as disadvantages.
• They are energy efficient which means they save a lot of energy.
• They are eco-friendly.
• They offer unlimited amounts of hot water as they are not limited by the capacity of the storage tank.
• They offer constant water temperature as they do not rely on how much heated water is stored in a tank.
• They are small in size which means they can be mounted on walls.
• It takes several seconds to a few minutes before hot water starts flowing out of the faucet. This makes shorts uses, such as washing of hands, somewhat impractical. Due to the time it takes to wait for hot water to flow, the initial flow of water which is unheated is wasted.
• The heater will automatically switch off if it detects the flow of water is too low. This is probably because the heater has a failsafe switch that allows it to detect a low flow of water, which for instance is caused by faucet that is not fully closed. The main disadvantage with this failsafe switch is that the users may end up using more water.
• The heating capacity of tankless gas water heaters may not be enough to heat water up to temperature during winter times.
• These types of water heaters require more maintenance as compared to storage tank types.
• There are certain models that require its vents to be made of stainless steel and not galvanized steel, something which can cost to several hundred dollars.
• They require high gas pressure. Something which some areas will not be able to accommodate due to their low gas pressure.
• The warranties of these products are very strict and these warranties can easily be voided if the unit was not installed by licensed plumbers or the unit has not gone annual maintenance.
Tankless gas water heaters will have a maximum flow rate that ranges from 2 gallons per minute (GPM) to 7 gallons per minute (GPM). This comes with a temperature elevation of around 45°F on the water outlet. The flow rate can still be increased, but at the expense of the water temperature. Most households will consider 2 GPM too low, except of course during the summer months. Manufacturers however recommend 4 GPM as the minimum requirement for single applications, such as shower, washing machine, or dish washer with each tap being opened one each time. If you plan on using two taps simultaneously, then it is recommended to have around 6 to 7 GPM.
The ignition system of a gas water heater can be powered by electricity, battery, pilot light, and water turbine ignition. Electricity is the most simple and reliable way to ignite the gas of your gas water heater. The only drawback with an electrical ignition system is that it will not work during power outages. Battery can also be very reliable. However, you need to replace the batteries when they run dry and this usually happens when you are in a hurry. The Pilot Light can be reliable as long as the light is not blown out should there be no automatic damper on the vent. The Water Turbine Engine is a turbine the spins from the flow of water and thereby generates electricity to power the electrical ignition. The main problem with this type of ignition system is that the turbine can sometimes jam, especially if the inlet water is not being filtered.
These days, thanks to computer controlled heaters, you can now control the temperature level of the water. It will provide you with a steady water temperature even if you increase or decrease the flow of water. Even with the advantage of computer controlled heaters, this can still sometimes be unreliable due to factors such as water pressure and gas pressure. Since they are digital, they often rely on electricity which is why they will not work during power outages. Manual controls on the other hand are by far still the most reliable. The main problem with manual controls however, is that you constantly need to regulate the temperature should there be a sudden increase or decrease in the flow of water.
Picking the right type of tankless gas water heater is not as easy as it may seem, especially when you try to consider the required piping and ventilation. Before purchasing a tankless gas water heating system, it is suggested that you consult a qualified plumber first before making any decisions. The plumber will be able to advise you regarding what brands he is familiar with and is able to service, which brands are reliable, which brands are good, and which brands can fit your budget. The plumber will also be able to advise you, based on the size of your home, whether you will need small electric tankless water heaters which can be placed near the point of use to increase the temperature of the water, depending on the heating requirement. Using both gas and electric water heaters in conjunction may in fact serve as leverage in helping increase the efficiency of your main water heater, which of course would be the tankless gas water heater. In fact, this tandem can even be more economical than using a 40 gallon tank water heater.