# solar energy water heating system part 3

The higher the solar energy factor, the more efficient the water heater. On the contrary, the more efficient the water heater system, the higher the price for installing it. In my last post’s example we knew that the SEF of the electric auxiliary tank system, which is 2.0, is higher than that of the fuel auxiliary tank system, which is 1.1. That means installing the electric auxiliary tank system will cost more than installing the other less effective system. However, it is not enough to only have the difference of the price of installing two systems to estimate the eventual total payback per year. In addition to compare the installing price, we still need to add the annual operating cost of the two system we figured out last time into the whole calculation:

Additional cost of more efficient system = Price of System Model B (or A) – Price of System Model A (or B)

Estimated annual operating cost savings = System Model B (or A) Annual Operating Cost- System Model A (or B) Annual Operating Cost

And finally:

Payback period/years = $Additional Cost of Model B (or A) /$Model B’s (or A’s) Cost Savings Per Year

Based on your personal situation, calculating the payback period per year of the two system and comparing them. The shorter the payback period, the more economically efficient and appropriate for you.

## 3 thoughts on “solar energy water heating system part 3”

1. Sarah D (swd5237)

My parents bought a solar energy water heating system for their pool. It heats the pool utilizing less energy and for less money than electric pool heating systems. It keeps the pool at a comfortable temperature and works fine. The only problem is the plethora of overcast days that draw from the solar heater’s efficiency. If you think about it, it isn’t a huge problem because these days are often rainy and colder, so no one really wants to go swimming anyways.

2. Wei Dai Post author

It depends on your personal situation. What I give is a way to calculate whether the system you chose is efficient and cost appropriate relate to your personal situation.