Is whole house fan a good investment for rental property

[Jin Zhang]

Hi everyone, I have two units in San Jose CA which I just started to rent out as STR and MTR. They are older properties and do not have an AC. Even though it is not super hot all the time in the summer, it will have about 7 days reaching 90 or higher from June to September. It could get a bit uncomfortable in the late afternoon. I do not want to install an AC. Because they are very expensive to install in Northern California. To improve the comfortable level, I am considering installing a whole house fan. But they are not cheap neither. Also, adding them will increase my electricity bill. Electricity is very expensive and kept on increasing in CA. I am not sure if they would be a good investment and what kind of return I could get on it. My thoughts is that the pros is with whole house fan and improved comfortable level, it could improve occupancy rate. But the cons is that this might increase my electricity bill. I do not know what I should do. If you are in my shoes, what would you do (which option would you choose) and why?

1. Install a gable fan

2. install a whole house fan

3. Install a whole house fan + gable fan 

4. Do nothing and keep it as is 

Thank you! Any input is greatly appreciated! 

Best,

Jin