First and foremost, if you are new to the world of onsen going, then make sure to check out onsen etiquette guide as well as our guide to finding an onsen in Japan.
By "types of onsen" I am referring to the facilities themselves, not the chemical composition of the springs. Even though, "onsen" is used as a catch-all phrase for any sort of public or private hot spring, there are actually a lot of different types of bathing facilities, not all of which are open to the public. Many hotels and resorts have pretty amazing baths but often times they are not open to the public unless you are paying guest. Let's take a look at some important onsen distinctions...
- 日帰り温泉 (higaeri onsen)- This literally means "day trip onsen" and it denotes a facility that allows guests to only use the bath area without having to stay over night or make reservations (in most cases). For the most part, onsen tend to advertise this on their homepages and on travel websites. If you are unclear whether or not an onsen is day trip friendly then you should definitely call in advance.
- 予約要 (yoyaku-yo)- Literally, "reservation required." This tends to only apply to select onsen, especially ones that also double as hotels and/or spas. Sometimes you have to buy a full meal plan in order to enjoy the bath (see below)
- 日帰りプラン (higaeri puran)- This is similar to the above "reservation required" facilities. Basically, you have to buy a meal package in advance in order to use the bath. This is common at traditional Japanese ryokan style hotels and often times it is quite expensive.
- 宿泊客のみ (shukuhaku-kyaku nomi)- Literally "overnight guests only." This means that the onsen is closed to everyone but the guests currently checked into the hotel.
- 組合温泉 (kumiai onsen)- Literally a "union onsen," meaning that only members of a select group (farmer's union, local neighbourhood association, temple association, etc.) can enter. Usually kumiai onsen are not market on tourists maps and are located near civic centres or neighbourhood association buildings. Although these are generally not open to the public, it is popular to by an annual membership if you meet the relevant criteria.
- 貸切温泉 (kashikiri onsen)- As LP recently explained, kashikiri baths are basically small, family sized baths separate from the main onsen. These are not available at every facility, but if they are then you usually have to make a separate reservation in advance. Some onsen have other rules such as a minimum number of guests in order to reserve one kashikiri bath or requiring you to be a guest in the hotel.
Also, some hotel onsen have designated times for bathing-only guests in order to make sure the main bath is not crowded when the over night guests arrive. In my own personal experience, I have seen onsen close to the general public as early as 2:00 PM. Therefore, even if the onsen does accommodate higaeri customers, make sure you check the hours of operation.
Furthermore, some hotel and non-hotel hot springs require reservations during busy periods such as during Golden Week and the start of the New Year. Hot springs tend to be particularly crowed at the start of January do to the traditional hatsu-buro (初風呂) or the first hot spring bath of the New Year.