Debating between a liquid cooled or air cooled for my parents house.

Going to visit my parents (semi-rural Illinois) and debating on getting them the Costco deal Kohler or one of the smaller liquid cooled ones. I calculated their max load at 18k, so looking at 20k min.

Doing the install myself and offsetting it about 15 feet from the house so the noise and CO2 is minimal and furthest from bedrooms. I really don't think they would be out for more than 4 days, so I think an air cooled one is enough if maintained correctly.