What our model shows

• A winter cluster runs on surprisingly little power. On a simulated mid-January day in Edmonton, about 8,300 bees put out 13 to 15 W combined in our model, roughly the glow of a dim night-light, and burn about 94 g (a bit over 3 oz) of honey.
• The core stays warm in deep cold. In our model the cluster core holds near 27 °C (81 °F) that day, while the outer shell of bees sits around 10 °C (50 °F) and outside air runs from about −15 °C (5 °F) overnight to −5 °C (23 °F) in the afternoon.
• Bees make water as they burn honey. In our simulation, about 12 g (roughly 0.4 oz) of water condenses inside the box on that January day, all from the bees' breath.
• Across a full year, that adds up. Over a full-year Edmonton run in a single deep wooden hive, the colony in our model burns about 72 kg (about 159 lb) of honey and about 1.4 kg (about 3 lb, or roughly 1.5 quarts) of water condenses inside the hive.
• Winter stores run down. In our simulation, stores fall from 24 kg (about 53 lb) in fall to about 8 kg (about 18 lb) by spring, while the cluster core holds 27 to 36 °C (81 to 97 °F) as outside air averages down to −15 °C (5 °F).

These numbers come from our computer simulation, not from sensors in a real hive. The model hasn't been checked against field data, so treat them as illustrations, not measurements. Daily figures are 3-hour averages, so real overnight lows run a bit colder.