So I've been researching and researching and I'm still confused...

Here's the deal. I have a 50 gallon electric water heater I was considering plumbing two Beacon Morris K120 kickspace heaters to. Other water draw from that heater is insignificant.

So I have the two heaters both plumbed about 5ft each from the HW heater with insulted PEX on single zone. The heaters are capable of putting out up to 9700 btu at 140 degree water. But I know the heater will operate only one 4500 watt element at a time which I understand to translate to ~15000 btu. Does that mean I will only have a possible 15000 for the two heaters to put out?

And what would this cause my heater run time to be? I'm assuming my loss will only put the return water to around 130 if that. Is that right? So would that cause my water heater to be running continually if the circulating pump is on?

I'm just confused on how these numbers all correlate and the affect on the water heater run time if I'm cycling it. My electric cost right now is .12/kW and it seems I'm only paying around $20 a month to run this water heater currently.

Does that make sense to anyone? Or do you need more info?

Thanks for any guidance!!