Joules/hour to Calories (th)/hour

When you're tracking energy budgets over hours — passive house heat loss, slow battery self-discharge, biological calorimetry — expressing rates in J/h matches the timescale of your measurements. A passive house losing 36 MJ/h is more intuitive to a building physicist than "10 kW" because they're calculating daily heat budgets in megajoules. It's a unit of convenience, not necessity.

One kWh = 3,600,000 J, so 3,600,000 J/h = 1 kW. The relationship is elegantly circular: if you consume 3.6 MJ/h of power, you use exactly 1 kWh of energy each hour. This makes J/h a natural bridge unit between the SI energy world (joules) and the practical electricity billing world (kWh). Multiply J/h by hours and you get joules of total energy; divide by 3,600,000 and you get kWh.

A Passivhaus-certified building targets heat loss below 54 MJ/h (15 W/m² × 1,000 m² for a typical house). A standard older home might lose 180–360 MJ/h (50–100 kW) on a cold day. The difference is dramatic: triple glazing, 300mm insulation, and air-tightness can reduce heat loss by 80%. Building energy certificates in some countries express this in kWh/m²/year, but the underlying calculation uses J/h or W.

About 230,000–290,000 J/h (65–80 W). This drops from your waking basal rate of ~290,000–360,000 J/h (80–100 W) because metabolic rate falls 10–15% during sleep. The heat warms your bed and room measurably — two people sleeping together can raise bedroom temperature by 1–2°C overnight in a small, well-insulated room. It's why you wake up warm even without the heating on.

Not directly — most building codes use watts per square meter (W/m²) or kWh/m²/year for energy performance ratings. However, the underlying heat transfer calculations in standards like ISO 13790 effectively compute in J/h when assessing hourly energy balances. Some German and Swiss engineering tools output intermediate results in kJ/h or MJ/h. The unit lives in the calculation layer, even if the final certificate uses more familiar units.

Ecologists track energy flow through ecosystems: sunlight → plants → herbivores → predators. Each link is quantified in cal/h or kcal/h per square meter. A temperate forest floor receives roughly 500,000 cal/h/m² of sunlight; plants capture 1–2% as biomass. A field mouse consumes about 3,000–5,000 cal/h in food energy. Expressing everything in cal/h makes the efficiency losses at each trophic level immediately visible.

A factor of 1,000. Since 1 kcal = 1,000 cal, 5,000 cal/h = 5 kcal/h. Nutrition and exercise science almost always use kcal/h (the "food Calorie" per hour), while laboratory calorimetry might use cal/h for precision measurements. The confusion between small and large calories has caused countless errors in student lab reports. When reading older literature, always check whether "calorie" means the thermochemical calorie (4.184 J) or the kilocalorie (4,184 J).

A hibernating black bear's metabolic rate drops to about 15,000–25,000 cal/h (roughly 17–29 W) — only about 25% of its active resting rate. Its body temperature drops just 5–6°C (unlike true hibernators that cool near freezing), and heart rate falls from 40–50 to 8–10 beats per minute. The bear burns about 4,000 kcal/day entirely from fat reserves, losing 15–30% of body weight over 5–7 months of hibernation.

In pre-SI European engineering, heating systems were often rated in kcal/h. A standard European radiator might be rated at 1,000 kcal/h (1,163 W). German and Italian heating catalogs from the mid-20th century used kcal/h exclusively. The conversion to watts was mandated by EU directives in the 1970s-80s, but older buildings across Europe still have heating system documentation in kcal/h. Italian plumbers still sometimes think in "frigorie" (negative kcal/h) for cooling.

Radioactive decay heat in spent nuclear fuel rods: a few hundred cal/h per rod years after removal. Slow corrosion reactions in sealed containers. Heat generation in composting piles (2,000–10,000 cal/h per kg of compost). Bacterial metabolism in soil samples. The continuous heat loss through a single-pane window: about 200,000 cal/h per square meter in winter. These are processes too slow for per-second measurement but too fast to ignore over hours.