It's worth noting that managing humidity is why smaller A/C units (fewer tons) are often more efficient in practice. Residential A/C units are controlled by thermostats and an oversized A/C unit (often preferred by consumers because "I'm no expert, but bigger is better") will short cycle [1].
Or to put it another way, if the air conditioner is running hard the most likely culprits are the air conditioner and the weather. But since this is HN, it could be your server racks in which case give them their own A/C...which reminds me that dividing a building up into many small zones, each with separate control is a good way to design an efficient system and why I am a fan of mini-split systems and room air conditioners. The goal of A/C is to cool people not buildings.
Good luck.
[1]: Short cycling is quickly lowering air temperature to the point the thermostat shuts off cooling before a substantial fraction of the latent heat from water vapor has been removed from the conditioned environment by the system.
Our library actually has kill-o-watts available for lending.
If, as you say the problem arose "lately", it is probably your HVAC being over extended. For starters, buy one of these babies https://goo.gl/4YFNZt (you could return it afterwards :-) and take some images of all the rooms from inside and also from outside the house. It will basically show you if heat/cool is leaking from your house.
Follow it up with educating yourself using something like this provided by your local energy company https://goo.gl/HzY3QZ OR start with a simple checklist like this https://goo.gl/wx55iC and make sure all the bases are covered.
If you want to do spend a little and do a more professional job, get one of such guys in your area to come do an energy audit of the house https://goo.gl/mTmAeg .
For the right type of trees (grows fast, doesn't shed too much and doesn't fall over in a strong breeze etc), ask advice from a landscaper in yelp/craigslist. The garden section at some Home Depots might help you out.
More tips can be learned from just googling and learning about Passive Cooling techniques.
Even if every other electric appliance in your house doubled or halved its power consumption, it wouldn't move the needle near as much as the biggest energy user in the house.
If your AC is more than 5 years old, consider replacing it. Not only do they eventually wear out, wasting more energy, but newer ones can be more energy-efficient.
Consider buying a cheap mister for your AC's radiator. It uses a small amount of water to conduct the heat off the coils. Cool-n-save, Mist-n-save, Mistbox.. may want to soften the water you use to avoid scale deposits.
The smartest thing would probably be to explore a 5kW PV system on your roof. Not only will it remove heat from your roof but it will also save a lot on your air conditioning no matter how efficient it is nor how hot it gets outside. SC's government and utility incentives (visit dsireusa.org) look a lot like those in PV-friendly states from 5 years ago (which is to say, ridiculously good for the homeowner).
I seem to recall a refrigerated air unit will use about 15% of its energy to cool its hot side and about 85% to pump the heat from cold side to hot side. So even if this eliminates that entire 15%, you're still going to be putting a lot of juice into that heat pump.
At large scale, evaporative cooling works even in humid climates but by large scale I mean upwards of 20 tons [2] square feet plus a place to put industrial level noise.
[1]: https://en.wikipedia.org/wiki/Evaporative_cooler
[2]: The 20 tons is based on the current Trane US product line. It equates to upwards of 12,000 square feet of conditioned space.
Most A/C units will work perfectly fine for 10-15 years if proper maintenance is being done.
Also another good one is clean the coils on your AC. Its the same concept. If air can't flow through the coils then your AC will work a lot harder and suck up more energy.
If you live in a area where it cools down at night and don't have a lot of humidity, then look into buying a whole house fan. I live in the Denver area and it will really cool down my house quickly.
Take a look at the changes that you've made lately with your power consumption, and what's gone up. Once you've narrowed it down to your air conditioning, you can do something about that problem.
(Important note: The biggest use of electricity isn't always air conditioning. But after a hot summer... it's air conditioning.)
So plugged in, your devices are consuming something like (don't quote me on this) $.007 per minute or something like that, and then unplugging them, but leaving their cords plugged into the wall is still consuming something like $.003. It all can add up over the month.
This includes any ceiling fans... they may be turned off, but if they are plugged in, it's still consuming resources.
If your house isn't well designed and constructed for passive heating/cooling/insulation that's probably a whole other can of worms to identify and fix