Foam gutter guards
Being the biggest non insulated space from your house, you cold really save money with the bills if you seal the garage properly.
When the garage has common walls with the rest of the house, you will really waste energy with heating, so the solution is you completely insulate the garage. The process only involves getting an insulation kit which is really affordable compared to the money you loose with energy.
There are two types on insulation for the garage. One is the reflective foil insulation which involves an aluminum foil of 5/16th of an inch thickness inside two layers of polyethylene foam.
Even easier to install are the polystyrene panels. If you want to call for an installer you can, but it is a job you can do yourself. Added to the kit you will need a tape measure, straight edge, and a knife.
Actually, sealing the garage doors is even an environmental friendly task, because you save up a lot of energy loss. Just get the insulation kit and follow some simple installation procedures.
Usually insulation kits come in standard door sizes but you can get them for more unusual sizes. If this is not an option, you must appeal to the reflective foil kit.