An electrical cost is wrong by the time zone.

Night electric power is cheaper by 65-75% than noon.

Therefore, electricity is supplied in the daytime by the solar optical generation of electricity, and the rest is sold to the electric power company.

It makes use of cheap electricity at night. It is effective to use the electric warm water vessel which makes hot water on the first advantage by the cheap electricity and which it saves in together. That is more economical than gas.