I'm not sure about AC. In automobiles the MIT Auto research center found electrical to have superior efficiency. But they have the added issue of managing optimal engine speed and load versus optimal compressor, even when part of a hybrid car.

Honda chose natural gas to take advantage of existing heating infrastructures and avoid lots of pollution control issues. They could have used heating oil (which is diesel with different additives). But then they would have had lots of pollution control features added to the cost.

What is happening on the commercial and industrial scale are:
1. All sorts of interesting heat recovery combined with AC. The absorption boiler air conditioner is well adapted to use with low temperature waste heat. They are common in commercial locations when waste heat is already available.
2. Combination hot water/ AC systems are sold. These are electrical heat pumps, much like those that commonly are use for whole house air conditioning. But instead of having fans and radiator outside to dispose of heat, they heat the hot water tank. The equipment sizes, costs, and operations do not make sense for household use. These are found at commercial sites that need both hot water and AC.

The special need that has funded a lot of research is the military and field operations in general. They need highly mobile power sources, and are much less sensitive to cost. There are lots of interesting mobile and semi-mobile power applications. The biggest areas at the moment are power efficiency (to reduce the demand), batteries (to improve power/weight, storage/weight, and reduce volume), and mobile power sources. Rugged solar panels are becoming common. They are a bit heavy for back pack, but horseback sizes can do a lot.

The most common operational model is a battery charger at camp to recharge the numerous little batteries in radios, GPS, lights, etc. Then the soldiers just need to carry the batteries in the field. The whole thing needs to be easily packable whenever the camp is relocated.

For covert operations you cannot use noisy things like engines as a power source and you cannot use noisy things like helicopters to move camp. All the supplies need to be carried by people and animals (horse, mule, etc.).