What This Calculator Measures — and Why the Numbers Surprise People
Most bone broth guides say the ingredient cost is close to zero because you use carcasses and scraps you saved in the freezer. That part is true, but it ignores electricity. A 24-hour stovetop simmer on a medium-low burner consumes roughly 2 to 3 kWh. A slow cooker running 24 hours uses about 1.4 kWh. At the US average of 16 cents per kWh, you're looking at 22 to 48 cents in electricity per batch — not huge, but it's real money that store-bought comparisons always miss. Add glass jars, apple cider vinegar, onion, garlic, and peppercorns, and a "free" batch actually costs $2 to $5 before you account for bones you purchased.
The Core Formula
Cost Per Quart = (Bone Cost + Aromatics + Electricity + Jar Cost) ÷ Quarts YieldedElectricity = (Appliance Watts ÷ 1000) × Simmer Hours × Electric Rate. For a slow cooker at 200W running 20 hours at $0.16/kWh, that's 0.2 kWh × 20 × $0.16 = $0.64. For a stovetop burner at 1,200W, the same duration costs $3.84 — six times more. The appliance choice is the single biggest lever in this calculation once bones are free.
Typical Input Values to Use
- Bone cost: $0 (saved freezer scraps) to $6 (retail beef soup bones). Chicken carcasses from a rotisserie bird run about $1-$2 each; 2-3 per batch is typical.
- Aromatics and vinegar: $0.75 to $1.50 per batch. Onion, celery, carrot, a few peppercorns, a tablespoon of apple cider vinegar. The vinegar helps extract minerals and costs roughly 10 cents per batch.
- Simmer time: Chicken broth 12-18 hours, beef/pork broth 18-36 hours. Pressure cooker cuts this to 3-4 hours with similar collagen extraction.
- Appliance wattage: Slow cooker 150-250W, electric pressure cooker (Instant Pot) 700-1,000W but runs far fewer hours, stovetop burner 750-3,000W depending on setting.
- Yield: A 6-quart slow cooker typically yields 3-5 quarts after reduction and straining. A 3-gallon stockpot yields 6-10 quarts.
- Store-bought price: USDA organic bone broth runs $5-$9 per quart (Kettle & Fire, Bare Bones). Grocery store store-brand runs $2.50-$4.50. Compare apples to apples.
Common Mistakes That Skew the Numbers
- Forgetting stovetop wattage: A stovetop burner at medium-low runs roughly 750-1,000W — four to five times a slow cooker. A 24-hour stovetop batch can cost $2.88 in electricity alone at average US rates, versus under $0.70 for a slow cooker.
- Ignoring jar cost: Mason jars last years, so amortize them. 12 Ball wide-mouth pint jars cost about $12. Divide by 50+ batches and you get under 25 cents per batch. Still real money, just small.
- Over-estimating yield: Beginners often expect a full pot to yield a full pot. Expect 15-30% loss to evaporation over long simmers. A tighter lid or Instant Pot eliminates most of this.
- Comparing to the wrong product: If you make rich, collagen-heavy broth that gels when cold, compare to Kettle & Fire at $7+ per quart, not to watery store broth at $2.50.