Simulating Electrical System as back up for Solar Hot Water System

This sounds like a software specific question. Typically, the solar thermal systems support the water heating, but do not cover it completly...at least in Germany. It depends on many things, like climate for one, heat storage tank size, and so on. I would prefer if you model it, otherwise you need to prove that indeed an electric heating will not jump on during a typical weather year.

75% is a better option. This is more considerate in a review than 100% savings with a electric powered backup system in place.

In my own home, I have solar thermal heating support. It covers all the drinking hot water all year round theoretically, but only 10% of the overall heating costs if you take both heating the house and hot water into account. I would be interested as to the design and the actual number that the manufacturer is claiming as a "proposed" savings...if that number is indeed 75%. I need about 9 m² Solar Collector Area and a 750 L tank for 4 people. I would wonder how much you need for a hotel with commercial kitchen to boot.

I think the system may be modelled to take credit. Achelles, I would check if the software permit to simulate solar system with water heater.

I agree that 75% is typical and reasonable. This can be simulated however. If your software does not do it perhaps you could try RETScreen or perhaps the solar panel manufacturer could do these calcualtions for you. Actual calculations will be better received by the reviewer as compared to an assumed 75%.