There are many benefits to balancing the loads of the two legs of power in your electrical panel and here's why. A balanced load in an electrical panel means that the current flowing through one leg is equal to the amount of current flowing through the other "hot" leg. The closer these numbers are, the more balanced the load. When the amperage is split up equally, the neutral current is canceled out. But when the current is placed all on one leg, the neutral must carry the entire load.
Your utility company meter measures power demand in peaks. That way, the utility company knows just how much power you may use on a high demand day, say when it's really hot and you have many air conditioners and fans running. They are responsible for supplying you your peak demand of power. As your power demand increases, so does your electrical rate. So if you are running two 120-volt window air conditioners that draw 10 amps each and they are on the same leg of power, your demand is 20 amps on a leg. But if you place them on separate legs of power, now your demand is only 1 amps, get it?
This balancing of loads can be achieved by removing the electrical panel cover, carefully placing an amp probe over each of the "hot" legs, and recording the amperage draw while the panel is loaded heavily. This means turn on air conditioners, heaters, freezers, refrigerators, TV's, etc... that are normally running throughout the day and night. See if the loads on the legs are close to the same amount, or if they are completely different. If they are very different values, we call this unbalanced loads. This condition will cost you more on your utility bill.
Unbalanced loads can heat up one of the legs due to overloading while leaving the other just fine. This occurs when using single-pole breakers that load only one or the other of the two legs of power. The two phases each supply 120 volts of power, but in the case of 240-volt, double-pole breakers, both legs of power are used, which automatically split the demand current and balance the load required. That's why it is more efficient to install a 240-volt air conditioners that draws 14 amps (7 amps per leg) versus a 120-volt air conditioner that draws 14 amps on just one leg.
The key to balancing loads is to find two appliances or devices that normally run at the same time often in the home. This may be a refrigerator and freezer. Maybe a coffee pot and toaster will be used in the mornings for making breakfast? How about a microwave and a dishwasher? Then you may be drying your hair and someone else curling theirs. The combination are endless I suppose. I think you see the connections, right? Utilize common sense and learn your user habits to balance the loads in your home, save money, and this in turn will lower your demand factor, lessening your carbon footprint. Remember, opposite phases, equal current draw, big savings!
One more thing about balancing electrical loads, you may not always be able to more electrical wires from one phase to the other to accomplish this balance, at least without rewiring some circuits if they are sharing a neutral with another circuit. Let's say you have an NM wire with two hots, a neutral, and a ground wire. Each of the hot wires goes on a different phase so the neutral wire is balanced. If both were to be moved to one phase, this would cause an unbalance in the wire, which we don't want. Appliances like dishwashers, refrigerators, and freezers can be pulled out and rewired if need be to balance the loads. In older homes I know this may be a pain making the corrections, but the savings may be worth the time, effort and expense. In a new home that you are building, check out the loads of the appliances that you will be installing before the wiring is done and have the electrician load it properly for you to a balanced state. You will thank me later when the utility bill comes in the mail.