Portable Air Conditioners can be useful, but they are limited in their capacity and efficiency.

I bought two portable air conditioners several years ago. We bought the lake house, and it had no central A/C, just one split system unit. In that area, you rarely need air conditioning, but that year, there was a heat wave, and temperatures soared into the high 80's. In the later afternoon, temperatures could soar in the house to nearly 100.