AC expectation in Rental

[Jennifer Green]

I have a single family  three-bed two-bath home  that is 1554 square feet . I did not upgrade the AC when I renovated the home.  I'm renting it out and I have really great tenants.  The only problem is that the AC is too small for the house . At the same time it's  cooling well and functioning as it should.  Going by the 20 degree rule it's working just fine. However it gets to be a hundred to 104 where I am .  My tenants want to keep the house at 70 to 73° at all times regardless of the heat outside.  They now want me to upgrade the AC  which will cost quite a bit of money. I want to keep the tenants but the investment to upgrade is quite significant. I have to decide whether to upgrade at a price tag of around 8 to $10,000 or tell them no. Thoughts?