How much electricity or power does a Navien unit consume in standby mode
The Navien 240A consumes power even when it is not in use. Using a Kill-a-watt meter, the draw is measured at about 4 watts. Thus, over the course of a month, you could expect the unit to consume about:
4 watts x 24 hours/day x 30 days
= 2.88 kilowatts
Thus, the unit will consume about 3 kilowatt hours per month just in standby mode. Prices per kilowatt vary greatly, but in many areas of Canada, we would expect that to cost about 50 cents a month.
Note: This standby power draw (phantom load) may increase in areas of cold temperatures because this unit (as do most tankless water heaters) has a heating element in it to make sure nothing freezes when temperatures fall below freezing.