Heat-Pump Water Heater Plus Tankless Water Heater
I have a Rheem Marathon and do not want to replace it. However, we occasionally run out of hot water when we have company. This is rare, but inconvenient. Here is my quandry:
AELP has a heat-pump rate of 5.9 cents/kwh. HOWEVER, that rate also comes with a peak charge of basically $10/peak kwh on top of the total Kwh. The peak is computed at (Highest kwh usage in any 15 minute interval during billing period) * $10 + (5.9 cents * total kwh per billing cycle). Therefore, if your highest peak usage in any 15 minute interval was 12 kwh, you would have a $120 peak charge on top of the billed total kwh. Why? Because we are hydro and they want consistent usage and could care less about time of day.
Given this situation, I am considering installing a Rheem RTEX-08 AFTER the tank. My understanding is that this tank does not activate unless the water drops below the set temperature (is this correct)? It also has a max GPM of 4.8 – enough for our two showers when we are not using the tankless. In an emergency, we will still incur a +8 kwh peak charge. But this should be very rare and it is there, if needed.
1. Is it correct that the tankless will not activate unless the water temp is below the set temp?
2. Is this the best use for my situation?
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