hello everyone,
As a point of honest disclosure, let me first say that I work for a dealer of the SETS tankless water heater that is currently being discussed. I thought I might be able to offer some assistance.
First, the SETS tankless water heater is NOT a full on/full off appliance (unlike soem other brands). In other words, it does not automatically draw its maximum output power when it is on. The first element generally remains at full power, and power is modulated to the remaining element(s) to adjust the temperature setting to the desired level as controlled by the user, and in accordance with flow rate. So, if you are demanding a small flow of water say at a bathroom sink, the unit will draw far less power than if you are running a shower or other higher flow application. The Model 240, which is generally the largest unit we use for residential, runs at a maximum of 99 amps (120 amp breaker required in most regions), which will provide about 3 GPM of shower or bath temperature water in a colder climate.
Electicity prices vary considerably from region to region, however, the average cost per KW/hr is far less than the 35 cents listed by one poster. In fact, most householders will pay between $0.08 and $0.15 for electricity consumed.
So, based on the $0.15 per KW HR, running the Model 240 (24 KW) on FULL power for an hour would cost about $3.60, or $0.06 per minute. The actual cost will be less for most applications since the unit will rarely need to run on its maximum power setting, especially for low flow rate applications.
Now, let's say for a moment that you are indeed one of the unlucky minority that do pay more than $0.25 per KW/hr for electricity consumption. Yes, it will certainly cost more to operate a tankless water heater than my figures above(
$0.25 x 24 = $6 per hour or about $0.10 per minute -based on full power) however, the cost of operating your conventional water heater is equally magnified. The thermal heat loss of a traditional tank during standby (when you are not demanding hot water) generally equates to about 30% for an average family of 4 with typicaly hot water usage patterns - even more for smaller families or for casual-use recreational properties, etc. The tankless will reduce the standby loss to zero. In fact, in areas where electricity is most expensive, tankless water heating offers the highest $ value of annual savings and fastest payback on investment.
Tankless water heaters are best used for back to back hot water demands, although they will generally provide enough hot water for one large demand and one smaller demand at the same time (with a properly sized model). We would note\ generally recommend them for running multiple showers or other large demands at the same time - fortunately, for most households, simultanoeous showering is rare and adaptign to the use of hot water on a back to back basis is well worth the other benefits of using a tankless water heater.
Let me know if you have any questions,
