Fuck Summer. It's hot as Satan's armpit and twice as humid. But air conditioning sucks down so much power! Is there any way to stay cool this season without driving the power bill up through the roof? Yes, there is! It's cheap, uses very little power and is surprisingly low tech.
It's the humble evaporative cooler, which operates on the swamp effect. Named for the cooling effect swamps have on hot, dry air blowing through them. This happens because the act of evaporation saps a great deal of heat from the liquid, owing to a reduction in kinetic energy as it changes state from liquid to vapor.
This in turn cools the air. It does also humidify it at the same time however, so this won't work in an enclosed space because eventually the air will have all been humidified, and the effect only works on dry air. This is why, contrary to intuition, swamp coolers work best with a window open near them.
Probably the best thing about swamp coolers is how dead simple they are to make. You literally only need a pump for circulating water, aquarium tubing, a bucket, a fan, and some cloth or foam to serve as the evaporative surfaces for the water:
There are variations on this which use ice, and indeed they get the air even cooler, but then you're spending more energy to constantly replenish the ice. It depends how long you plan to use it for. If it's for long term use (more than a few days) I'd go with the circulating water design. If it's just for a weekend camping trip or whatever, use ice.
You might see small, desktop sized "portable air conditioners" for sale on Amazon these days. They aren't really air conditioners, those can only be miniaturized so far and are too energy hungry to run off batteries or USB. They're just small, stylish looking swamp coolers and in most cases are a waste of money.
Swamp coolers are already weaker than air conditioners, so really, the bigger the better. DIY swamp coolers are a popular item at Burning Man due to the abundance of hot, dry desert air and the fact that they can easily run on solar panels due to their low energy consumption.
They do of course consume water though, so be mindful of that. I've not done the math to see what the impact on my water bill would be, but it's a safe bet that it'll be markedly lower than I would spend to run an air conditioner all day, every day throughout the Summer.
Stay Cool!