Do you have vending machines in your library? Vending machines run very inefficiently. You can possibly cut your energy cost in half by looking into Vending Miser. Vending Miser is a sensing device that shuts down the cooling function after a set amount of time – especially great for overnight or holidays. Check out this PDF from Tufts University on the issue. Many local electric utility companies will actually install this device free of charge or provide rebates so check that out locally. Otherwise, the cost is about $150-$200, which you will get back in energy savings in about 1-2 years. For pricing and sales visit this Web page.
Washington State University has a great Web page discussing this idea, with links and stats, proving the favorable results the City of Portland has discovered from installing this device in many locations. Seattle also offers some first hand results. Check locally to see if this is happening in your town.