Max. water temperature
The highest water temperature provided by the device. The standard temperature of hot water in the water supply is 60 °C, and this value is actually the minimum for modern water heaters: models with more modest rates (usually from 40 °C) are extremely rare. But higher values can be found much more often: for example,
water heaters of 75 °C and
80 °C are very popular, and in the most powerful models in this regard, the temperature can reach
95 °C and even higher.
On the one hand, strong heating requires appropriate power (which is especially noticeable in the case of instant electric heaters). On the other hand, the higher the temperature of hot water, the less it is needed for a comfortable outlet temperature, after mixing with cold water; this reduces the consumption of heated water, which is especially important for storage boilers. In addition, many models have thermostats (see "Features").
Also, note that heating to operating values may involve different ΔT (degree of temperature change) — depending on the initial temperature of the cold water. The actual performance of the heater directly depends on ΔT; this moment is described in more detail below, in the paragraphs devoted to performance at different ΔT.
Efficiency
Heater efficiency.
Recall that efficiency is the ratio (in percent) between useful work and total energy consumed. In water heaters, this parameter is indicated mainly for gas models of an instant heat design. It describes what part of the heat from the gas burning in the combustion chamber is transferred to the water; accordingly, the higher the efficiency — the more efficient this model, the less gas it will need to heat a certain volume of water to a certain temperature. However, the increase in efficiency inevitably affects the price of the device; on the other hand, additional spending can quickly pay off due to gas savings.
In general, modern instant gas heaters have fairly high efficiency — from 81 – 84% in the most modest models to 90% or more in the most efficient ones.
Conversion to LPG
Possibility of converting a gas water heater to work from liquefied gas (in cylinders).
Recall that by default, all such devices are designed to be connected to the gas main. However, where it would be desirable to have a gas heater (for example, in a house with weak wiring), such a line may not be available. The only option in such cases is the use of liquefied gas in cylinders — and such a gas differs not only in higher pressure but also in composition (methane is standardly used in mains, propane in cylinders). Therefore, to switch the heater to liquefied gas, it is not enough to install a pressure reducer — you also need to replace at least the nozzles on the burner, and in some cases, elements of the ignition system. Technically, this feature is available for almost any gas heater. However, if the characteristics directly indicate the possibility of conversion, this usually means that the corresponding parts are immediately supplied with the device. Yes, and their installation is usually much easier than in a device where re-equipment is not initially provided.
Weight
The weight of the device, excluding the water collected (passing) into it.
