With August temperatures likely to be between 32*-35*C (90*-95*F), I would be surprised if your hosts didn't themselves shower daily, so you are unlikely to offend them. However, it would be good manners to let them know that you like a daily shower and ask if that is alright to do so in their house. They would probably appreciate you asking rather than you taking it for granted that it's OK.

I'm sure you'll have a great time in Granada.

In Spain it's once a day, even if you can also find some pigs who don't take a daily shower. In France, on the other hand, it's once a week, that's why they use so much perfume.

You can take one shower a day, or two if you need it, and the family in Granada shouldn't feel bothered at all.

I'm Spanish and I shower everyday sometimes twice a day. It's very hot this time of the year!

In Europe people take spit baths like Americans used to do before the relatively recent, post WW2 period of prosperity. My grandma took spit baths at the sink daily and only showered maybe once a week tops. She was always clean, but she didn't waste anything. This was common among women of her generation (b. 1911).

if you dont take a shower min once a day, u wont overstay there for sure

Nope. It's good to stay clean. I think they'd rather you not smell like an animal.

This may seem like a strange question, but I am about to spend a semester in Granada in a homestay, and I don't want to overstay my welcome by showering too often and making their water bill higher. I generally take a short shower once a day, is that considered excessive?