Are all the shower hot water in the hotel heated by solar energy?

Hotel hot water generally has the following types:

First, electric heating. Some are central heating, and some are similar to household water heaters in guest rooms. Disadvantages: If the occupancy rate is low, it will be wasteful to pull out the room card frequently. Cold and hot, hot and cold.

Second, solar heating. Disadvantages: Solar heating will seriously affect the operation of cloudy days in winter or rainy days in summer.

Third, the combination of electric heating and solar energy. That is, when the temperature is lower than the set temperature, the electric heating will start automatically. At other times, electricity is not needed.

Recommend the third method.