I am a HOMER Pro licensed user. I was doing simulations including wind, solar and BESS and exported the simulation results. The results has 2 columns tiled "Generic 1kWh Lead Acid [ASM] Degradation - Time and Temperature" and "Generic 1kWh Lead Acid [ASM] Degradation - Cycling" (I have used "Generic 1kWh Lead Acid [ASM] model" as battery).  I have the following questions. 

1. What is the unit of both the columns mentioned above? I assume them as "percentage". 

2. How can I determine the annual degradation value from this? 

3. How can I determine the degradation at the end of 25th year from this? 

1. Yes, you are correct. The units of the "Generic 1kWh Lead Acid [ASM] Degradation - Time and Temperature" and "Generic 1kWh Lead Acid [ASM] Degradation - Cycling" columns are the cumulative percentages of the battery's rated capacity that has degraded by that timestep. 

2. If you scroll all the way down to the last timestep of the year (12/31/2007 11:00pm in the attached example) you can see the Time and Temperature degradation totals 1.195% while the Cycling degradation totals 2.999% (see screenshot below).

If you take a look in the Library at the Generic 1kWh Lead Acid [ASM] component, you can see the default setting to calculate the end of life / replacement of the battery is by taking the larger of the two degradation sources (see screenshot below). If desired, you can change this setting by copying the component into your library. Therefore, the amount the battery has degraded after the first year = 0.02999715*1kWh*quantity of batteries.

You can calculate in what year the battery will be replaced by dividing the degradation limit of 20% by the larger of the two annual degradation percentages (2.999% of cycling degradation). This equals 6.667 years, which correctly corresponds with the battery being replaced in Year 7, as seen on the Cash Flow tab of the Simulation Results window (see screenshot below).

3. If using Multi-Year, you can export 25 years worth of timeseries data and you can see the cumulative degradation percentages increase until one of them reaches 20%.  The battery will likely be replaced before the end of the 25 years, but you can determine the degradation of the battery in that last timestep by multiply the larger degradation percent by the rated capacity and quantity of batteries, like I showed in #2.