On mine, the electric element in the Hydro/AquaHot uses 12.5 amps. (1500 watts divide by 120 volts equals 12.5 amps) That amount is verified by the readout on the Aladdin. 12 amp can make about 5,000 BTUs.
12 amps is the same as a single $20 WalMart space heater and no more. Worse, it spreads the limited heat everywhere, including the tank bays and for hot water. It might be enough to provide primary heat if the outside air temperature is around 60F or higher and the wind isn't blowing.
Some AquaHots have two 12 amp elements, and that can be better. Some Beavers have an electric heater behind the baseboard under the kitchen counter that is completly separate from the Hydro/AquaHot. It is there because the Hydro/AquaHot can't do the job on electric only by itself.
Electric is a secondary source of energy in the Hydro/AquaHot design. It has enough "power" to keep the coach from freezing from about 25F and up if the wind isn't trying to take all the heat away.
"How does one use their diesel?"
You turn on the switch and the Hydro/AquaHot diesel burner lights up. It is a burner made by a German company and is branded "Webasto". It draws motor fuel from your tank and, depending on model, produces around 50,000 BTU. That is 10 times greater than what the electric element can do.
Some Hydro/AquaHots are set up so that with both the electric and diesel switches on, the diesel does not fire up until the electric can't keep up. Others, like mine, cycle both on if heat is called for.
"but what about when dry camping or even being on 50 amps at a campground? Does running the generator (which is using diesel) do the same thing?"
Running the generator will make more electricity available, but the Hydro/AquaHot can still only use 12.5 amps. So plugging in to a 100 amp service or running the 7500 watt Onan does not make more heat. (We call it "50 Amps" but there are two breakers, so the total is really 100 amps.)
If you really want electric heat and have the 100 amps available from the park, you can do it. Start with the Hydro/AquaHot turned on. Add a space heater and plug it in anywhere. There is a limit because the wiring for the regular outlets goes through a 30 amp breaker. I like using the "baseboard" style, but any space heater will work. I like running two set to the low setting of around 8 amps. One is in back and one is in front. With the two heaters and the Hdro/AquaHot that is about 30 amps and maybe 10,000 BTUs. It certainly works better.
If you need more electric heat, you need to find circuits that are not on the outlet circuit. For example, the washer/dryer plug would support another heater.
Another way to heat with electric when you have 50 amp hookups is to use the Heat Pumps capability of the air conditioners. You select Heat Pump instead of Furnace on the thermostats and those noisy things will blow hot air at you. They work well down to about 40F, but as you approach freezing temperatures outside they loose most of their efficiency.
Hope this helps for those that are new to the Hydro/AquaHot. Please phone if you have questions.