NEMA stands for National Electrical Manufacturer Association. NEMA ratings are standards that are useful in defining the types of environments in which an electrical enclosure can be used. The NEMA rating system is defined by the National Electrical Manufacturer Association, and frequently signifies a fixed enclosure's ability to withstand certain environmental conditions.
The IP Code (or International Protection Rating, sometimes also interpreted as Ingress Protection Rating) consists of the letters IP followed by two digits and an optional letter. As defined in international standard IEC 60529, it classifies the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in electrical enclosures. The first IP digit refers to solid objects and the second digit refers to liquids.
The inverter, charge controller or battery enclosures are usually referred with NEMA ratings. The IP code is rarely mentioned, especially for the junction box of solar modules or for indoor electrical devices. There is a NEMA rating table that goes from 1 to 13; however, only some of them are applicable in solar industry.
Here is a table that would help you with NEMA and IP codes:
NEMAIPxxDescriptionNEMA-1: General Purpose - IndoorIP20: Protection against solid objects up to 12mm.Type 1 enclosures are intended for use indoors, primarily to prevent accidental contact with the enclosed equipment, in areas where unusual service conditions do not exist.NEMA-3: Dust tight, rain tight and sleet resistant - OutdoorIP64: Total protection against dust and protection against spray or water from every directionType 3 enclosures are intended for use outdoors, to protect the enclosed equipment against windblown dust and water. They are not sleet (ice) proof.NEMA-3R: Rainproof and sleet resistant - OutdoorIP22: Protection against solid objects over 12mm and against direct spray up to 15° from vertical.Type 3R enclosures are intended for use outdoors, to protect against rain, and meet the requirements of UL 508 "Rainproof enclosures". They are not dust, snow nor sleet proof.NEMA-4: Watertight and dust tight - Indoor and outdoorIP66: Total protection against dust and protection against strong jets of water.Type 4 enclosures are intended for use indoors or outdoors, to protect the enclosed equipment against splashing water, seepage of water, and severe external condensation. They are sleet resistant but not sleet (ice) proof.NEMA-4X: Watertight and dust tight - Corrosion resistant - Indoor and outdoorIP66: Total protection against dust and protection against strong jets of water.Type 4X enclosures have the same provisions as Type 4 enclosures and, in addition, are corrosion-resistant.NEMA-12: Industrial use, dust tight and drip tight - IndoorIP55: Protected against dust and protection against low pressure jets of water from every direction.Type 12 enclosures are intended for use indoors, to protect the enclosed equipment against fibres, flyings, lint, dust and dirt, and light splashing, seepage, dripping and external condensation of non-corrosive liquids.