The basic requirement of Channukah is a flame, a person, and a house. A house has an inside and an outside, and the Channukiah relates to both of them.
The ideal place to place the Channukia is by the door, just outside of the house but not too far from it. The next best is the windowsill, facing inwards and outwards. There's a message that the Channukiah projects. But what exactly is it? And who is the intended audience?
For centuries, there was a possibility that showing a Channukiah in public could cause anger and violence. In many places, it is still the default to light the candles indoors. Was it a show of Jewish identity in public that was dangerous? Or Jewish pride? Still, despite allowing for the possibility of hiding inside, the laws of Channukah push people to face the possible danger and go outside.
If everybody is at home lighting candles, who is watching them? The Other. There are people coming home from work, their mind absorbed with the Everyday. There are non-Jews, who never heard of the Channukah story. There's an interaction going on between those showing the lights and those watching them, played out through the Channukiah.
What exactly was the miracle, and why is it so important to publicise it? There's the small story, of a little jar of oil that miraculously lasted for eight days. There's the military tale, of a small band of Jews taking on the mighty Greeks and winning back their Temple. And there's an identity story too, of a campaign to have Jews abandon their ritual practices, and the Jewish fight to remain distinctive and unique. Which one is being played out here by lighting the Channukiah in the public realm?
King David writes a psalm of thankfulness for being healthy, for having recovered from some sickness. So why is it titled "a dedication (Channukah) of the House?" It can't refer to the Temple, which wasn't built yet. Some commentators say that 'house' refers to his body: his recovery from the mysterious sickness was also called Channukah.
Each flame has to have a distinct identity. Even though the light of a bonfire is stronger, the distinctiveness of the smaller flames is more important. The flames have to be in a straight line, not too close together nor too far apart; to be appreciated as individuals.
We need "a flame, a house, a person." But the house also means a household, a community of people who see themselves as united. In this case, they share the obligation and one Channukiah is enough. A household can be a family, a group of friends, lovers; they can be in one place or spread out; a metaphysical bond turns them into one unit.