The good news is that summer is a great time for grilling and grilling is delicious. The bad news is that it's a total ecological disaster, especially if you grill with charcoal like a self-respecting member of human society.
The canonical research on this comes from Eric Johnson of Atlantic Consulting, who finds that charcoal has two huge downsides relative to gas. One is that producing it by smoldering wood is fairly energy-intensive. The other is that actual charcoal cooking is a hideously inefficient use of energy:
A propane grill works like a stove. It turns on when you want to start cooking, it channels heat in the direction of your food, and when you're done you turn it off. Charcoal, by contrast, gives off a lot of heat both before and after you're done cooking.
Of course whether you're using propane or charcoal, you are probably grilling some meat and as this Environmental Working Group chart notes meat is an ecological disaster:
Put it all together and a traditional cookout of burgers on a charcoal grill is a total ecological disaster. Grill some chicken on propane and you're in much better shape.
Best of all, however, is to be no fun at all and just stay inside eating raw nuts. Sorry.