I am not familiar with that particular unit but what happens in an "on demand" heater is as soon as the flow sensor closes, it ramps the burners as high as 100% no matter the load, so when watching an electrical boiler, the start up pulls almost full tilt for say 15 seconds, then it regulates the power to match the demand...
I hear ya, and that's why I contacted the company to ask about their control logic. With a boiler, it makes sense to dump max power until the water begins to boil because the water is going to reach a constant temperature at boiling, so it's all about time to temperature in that case. This unit isn't trying to boil water, though. It's just raising the temperature. Dumping max power doesn't get the water to temperature faster - it gets them to too high of a temperature. They could achieve the desired temperature rise by putting in a constant power load based on the flow rate, or they could pulse the heaters - but pulsing would reduce the life of the elements, I think.
This is all great advice, man, and I absolutely appreciate you taking the time to help me. Running the wire is the biggest obstacle to me, just because I've never done it. It would have to go from the electrical box on one side of my house, over (I'm assuming over into the attic) my kitchen, and then down into my garage where the water lines for the heater are located. I'm on the hook to review this in 30 days, so I'm thinking through how I can operate it and check out the functionality fairly quickly. If I can hook it up to an existing 240V line that is rated for around 40A (I have a 240V power cord with bare wire ends) and flow water through it, measuring temperatures and such, then at least I've used it. I already know some of what I want to put into the review - which is all the stuff that I hadn't thought through when I selected it. Such as, the cost of installation (I think electrical parts alone are near $250-$300 for my house, including breakers, wire, and other - not counting time/money to install), the power consumption, and the limitations on how much can be heated. They have a chart for how many showers and sinks can be on at the same time, but those are for 1.5GPM showers and 0.5GPM sinks. I'm fairly conservation oriented, but even I have a 2GPM shower head.
Anyway, time to get Niki out for her Christmas morning walk (well, ride to the park, then walk). Later!