The Penates are the household gods who watch over the penus - the larder the household store of a home. They were originally honoured at the family hearth but later came to include also the particular deities a family worshiped.
In the public cultus the original Penates were the Discouri, Castor and Pollux, whom Aeneas brought to Italy with him. And archeological finds confirm this.which?
"Keepers of the Fire"
/Quoting from: Crapsey, Algernon Sidney. The Ways of the Gods. New York: The International Press, 1920. (Out of Print)/
The hearth is the heart of the family life. To keep the fire alive on the hearth is the bounden duty of the family gods. We of the modern world have lost altogether those conception that made "hearth' and "altar" sacred words. Domestic religion sanctified domestic life. The Penates, who were the Spirits of Ancestors, were the "Keepers of the Fire and of the Store".
It was the domestication of fire that changed man from a savage, living upon roots and raw flesh, into a civilized being, feasting on roast beef and baked potatoes. It was the capture and taming of fire that made possible the home and the family. Because of this, the Penates, the "Keepers of the Fire", are the best beloved of the family gods. With them the family was intimate as it gathered around the hearth when the day's work was over; they were present when the house-father and house-mother gave bread and meat to the children and the slaves, and after the dinner was over the Penates inspired the members of the household to speak words of love and wisdom one to another. The husband could have a secret from his wife, the wife from the husband, but to the Penates all secrets were open. The light of their fire penetrated to the marrow to the bones. All profanation of family life was an offense to the Penates, to be punished by the heat of fever and the cold of the chill.
While the family slept, the Penates watched; all through the night the dull glow of their life was seen in the slow-burning brand lying in the ashes, that kept the fire alive on the hearth. If that fire died out, the Penates were disgraced, and the family shamed; for the life of the fire once gone was not easily restored.
"Guardians of the Store"
The Penates were not only "Keepers of the Fire", they were also the "Guardians of the Store". It was their duty to inspire the cook with skill to make delicate dishes for the family able, to watch the meat before the fire, to scare the rats from the cupboard. In the archaic world the gods were more useful than ornamental. The men and women of that world would laugh our gods to corn and think of them with pity, — gods shut up in churches, having nothing to do but to listen to the droning of prayers and the confessions of sins; gods who pass their dreary existence away from the warmth of the hearth, the smell of the cooking, the chatter of the maids and the stir of the family life!
A god upon a great white throne may have power and dignity, but for comfort and good-fellowship one must go to the god who sits by the fire, inhales the odor of spice, and the flavor of the bread and the cake and the meat that are cooking in the kitchen. Such a god can understand the tribulations of the cook and the annoyances of the mistress; he knows by experience that fire burns and ginger is hot in the mouth. All other religion is cold and formal beside this intimate religion of the hearth.
Les origines et le développement du culte des pénates à Rome (Collection de l'Ecole francaise de Rome)