First, you should distinguish between a "fjällstation" and a "cabin". A fjällstation is a youth-hostel type accomodation with up to 400 beds at the endpoint of a trail. Six of them are operated by the STF. You can reserve beds, buy material in a shop and eat in a self-service restaurant. You find more details on Abisko Fjällstation and Kebnekaise Fjällstation in the index page. Cabins are placed along the trails in the wilderness areas. You have to cook your own meal and care for everything by yourself. Most cabins are operated by the STF.
Inside the cabin, you find a combined "kitchen and living room". Electric power is not available, but I believe that you will not miss it here in the mountains.
The sleeping compartment has two- or three-storey beds. Out of season, you may be alone in the cabin. During season, it is more expensive and you probably have to share it with other hikers.
The following text is provided by the STF and explains conditions in a cabin.
STF Mountain Cabins
Huts on the mountain
To facilitate hiking tours in the mountains the Swedish Touring Club (STF) has built some 90 huts in about 50 places. The huts are of various types and sizes. What they all have in common is their strategic and often beautiful location.
A mountain hut offers a simple but comfortable accomodation. In the huts you will find a combined kitchen and day room, bedroom and drying room. The biggest huts have about 90 beds. Some huts even have a sauna. In a separate building you will find earth closet and woodshed.
The beds in the huts are wide and comfortable. Of course there are mattresses, blankets and pillows. You must bring sleepingbag or sheets. You share room with several other people but many huts also have four-bedded rooms. You cannot reserve beds in advance.
Half the pleasure during a hiking tour are the meals. You will find cooking utensils and crockery in the huts, you must, however, bring your own cutlery. For cooking there is Calor gas but the wood stove is still being used. Calor gas is only available during season.
From Pältsa to Storrödtjärn
The northernmost hut of the STF, Pältsa, is situated at Treriksröset in Lappland. In Dalarna you will find the southernmost hut, Storrödtjärn. The hut are situated 7 to 25 skm from each other along marked trails. The hut sites have been carefully selected. As starting point for excursions in the area the location is perfect. Kungsleden between Ammarnäs and Hemavan in Västerbotten is an example of a modern net of huts and trails. In STF's "Fjällhandboken" (only available in Swedish) you will find a list of huts and maps describing their location.
Fire, wood and water
The accomodation is based on self-catering, i.e. everybody chops wood, makes fire, fetches water, cooks and sees to it that that the hut is tidy when leaving. For supervision of the huts there are wardens during season, who also collect payment for overnight stay, for camping near the hut and for a day's visit. The huts are, with some exceptions, open from the beginning of March until the beginning of May and from the end of June until the beginning of September. During the rest of the year there is only one room open and that is an emergency room with no heating, no Calor gas etc. The "Fjällhandboken" shows present fees and opening dates.
As you can buy provisions at all STF mountain stations, all the huts in Jämtland and Härjedalen and some of the huts in Lappland, you seldom have to carry food for more than two or three days. Most of the assortment consists of tinned food. With imagination and maybe with some contribution from the nature, the dinner might still be a sensation in taste.