While crankcase systems aren't as common as they once were because of the negative energy impact they have, there are times when the energy savings aspect should be overlooked because the benefits of installing one far outweigh it. A crankcase will essentially keep the compressor warm, preventing refrigerant from condensing and watering down the oil that is necessary.
1. High Temperatures
If you live in an area that experiences sweltering or humid summers, adding a crankcase heater to your system could be a good idea. When the system isn't being used, the ambient temperature can allow condensation to form. Add the crankcase and use it only during these times for ultimate performance.
2. Previous Issues
Even those who live in areas that don't experience extreme temperatures, adding a crankcase can be worthwhile if you've had issues in the past. It's typically much cheaper to add this than it is to replace an entire system. It can be a do-it-yourself job, but a professional can ensure that you are getting a perfect installation and go over the differences with you, as well as advise you on how to take care of the system properly.