I have a 2004 water heater tank (80 gallons) combined with solar. Basically, solar panels heat the water and send it to a smaller conventional hot water tank that goes to the 80-gallon water heater tank. See pictures below. What happened is that in summer 2020 the pump that pumps water to the smaller tank broke. I called the plumber, got quoted $500 to replace the pump and I didn't feel like spending all that money. Now, I can clearly see that my electric bill increased on average by $100 per month since last summer (pic below), and that replacing the pump would have been a better idea. Now I am debating what to do. I don't wanna keep paying the extra $100 per month. Options are:

1) Leave everything as it is

2) Get a new pump. Does it make sense to spend money on the pump since the 17 yo heater could die any moment?

3) Get a new 80-gallon efficient heater. Any suggestion on the model? Am I supposed to keep the solar system and so also buy a new pump, or are they not compatible?

Thank you