Electric Element Heat-Up Calculator
Heat-up time for an electric brewing element and the wattage needed to hold a boil - power figures only, wiring is an electrician’s job.
Power figures only. This tool does not size circuits, breakers or wire - that depends on your local electrical code and must be done by a qualified electrician. Never guess high-wattage wiring.
How it works
Heat-up uses the same fixed energy as any heater - 4.186 kJ per litre per °C - divided by the element’s delivered power. Holding a boil is a different number: it only needs to replace the latent heat carried off by the steam, about 2257 kJ per litre evaporated, so a modest wattage sustains a boil that took a big one to reach.
energy (kJ) = litres × 4.186 × (target − start)°C
heat-up time = energy ÷ (element kW × efficiency)
boil-hold power (kW) = boil-off (L/hr) × 2257 ÷ 3600
The boil-hold figure is the latent-heat floor before kettle and ambient losses - real setups need a bit more, so leave headroom. For a gas setup, see the burner BTU calculator.
Sources: standard thermodynamics - specific heat of water 4.186 kJ/kg·°C, latent heat of vaporization ≈ 2257 kJ/kg.
Frequently asked questions
- What wattage element do I need?
- Two jobs decide it: heating up in a reasonable time, and holding a boil. A boil only needs enough power to keep evaporating water - roughly 1.9 kW per litre-per-hour of boil-off - but you usually size up so heat-up is not glacial. This tool gives the heat-up time for an element and the wattage needed just to sustain your boil. It reports power only.
- Can this tell me the breaker or wire size?
- No - and on purpose. Getting circuit, breaker and wire gauge right for a high-wattage element is genuinely dangerous to guess at, and it depends on your local electrical code. This tool stops at the power figure in watts. Take that number to a qualified electrician to spec the circuit.
- Are electric elements more efficient than a burner?
- Much - an immersed element puts almost all its heat into the wort (roughly 95-100%), versus 30-50% for an open propane flame. That is why a 5.5 kW element keeps pace with a far higher-BTU burner. Efficiency here is only shy of 100% because of heat lost through the kettle walls and surface.