They have the double coat so it is not the same as other cat breeds. It gets hot and humid here in Saitama, Japan. While we use aircon, we do tend to leave it off when going out and my 8 year old cat likes the unairconditioned areas. Should you shave to give him more comfort in summer and how?
I personally have a long hair double coat cat (Maine Coon) but most my info comes from reading Husky forums.
Here is what some online forums say: Shaving is not necessary for a double fur cat. It seems like it would help to us but many breeder specific pages are extremely against shaving pets (especially double coat animals like Huskies or Maine Coons). The reasoning is because it can stress out the animal, permanently mess up the undercoat, and generally doesn't help as much as much as we think it would. The double coat can prevent heat as well as insulate in the same way as house insulation works. Sometimes cutting the coat can actually make them warmer and put them at higher risk for sun exposure (huskies more than cats). If your cat doesnt display signs of overheating then the cat is probably fine. There are a couple things you can do to help the cat when you are away.
Helping keep cool: To help your cat keep cool you can do a few things. Some musts for any double coat breed is to provide plenty of shade and fresh water. This can help the animal cool down tremendously and is an absolute requirement in a warm summer with a double coat. You can maybe run a fan on the floor when you are away and see if your cat curls up in its path (it may not go too close because it is bothered by the breeze but it could still like the air flow). If it doesn't ever happen then you can probably stop running the fan if you want but i am always for some type of air flow or coolness option for pets. Another thing you can do is put an icepack in a sock near where they lay down (like if you have a hide or a mat or something). This can help cool them down and it is relatively cheap and easy to implement for when you dont have air conditioning. Another thing to remember is that without air condition you should reduce playing with your cat because if they run around a lot they can overheat. Now you say you turn off the AC when going out so this shouldnt be a problem since you do run AC sometimes.
My experience: I am by no means a certified vet or breeder. I am coming from a stance of owning a Maine Coon for a few months. I picked up my cat from a family that did shave him in a lions cut to try to tone down the allergies of their daughter. They told me he acted really sheepish and scared when they shaved him and that he barely interacted with them for a long time (they humanized it by saying it was "embarrassment" but i dont agree). This is probably from the stress of the shave and judging from how they talked about it it seems like it lasted quite a while. I cant even imagine him acting sheepish because he jumps on my face every-morning and greets most people that come to my place with a headbutt so the stress from shaving can have a significant impact on their behavior. My AC was broken for a few days where the temp was over 30C and my cat would sometimes lay in the sun still. When he was hot he would go get a drink then go under the chair in my living room. Cats are not like snakes and they can manage their comfort to a decent degree, meaning if they get hot they will find a cooler place to lay.
I also brush my cat all the time and that keeps the fur from matting and helps thin the coat slightly by brushing out dead hairs in the coat and undercoat.
In the end I am against shaving/cutting pets with a double coat. It seems to be a very controversial topic but that is my stance. I think there are things you can do to help cool them down and if you keep them brushed and provide shade and water they can still be comfortable. I personally think your cat is probably fine and there are small things you can do to help if it needs to cool down. The fact that you run AC or something similar when you are home and the fact that the cat is indoors with access to shade means that it wont be hot all the time. You can maybe think about running a small fan or do the icepack thing if you are really worried or it gets > 35C but i wouldn't worry about it too much unless your cat starts displaying signs of heatstroke or overheating.
Our domesticated cats hail from desert areas, meaning they can handle heat and should not be shaved, as it is an aspect of their ability to keep cool and doing so can cause them harm. (Willowbrook Vet or any search will show this.) I personally turn all things off when I leave--cats get into trouble, especially with anything with moving parts. I leave the AC on but at a higher temperature, as cats used to be used in smithing because they could sit in the hot areas and not be bothered while waiting for mice.