Our calculation methodology

Three kinds of calculation

Physics-based calculations use established relationships such as energy = power × time. Guideline-based estimates adapt published sizing guidance. Empirical estimates use practical assumptions and should be treated as a starting range. We label these differences on every tool.

Electrical energy and running cost

E (kWh) = P (W) ÷ 1,000 × t (hours). Cost = E × electricity rate. Rated power is not always average power: thermostats, compressors and variable-speed motors cycle. Use measured energy or an energy label where available.

The general cost tool annualizes the selected monthly schedule over 12 months. Weekly cycle tools use 52 weeks per year and divide annual cost by 12 for a monthly average. Currency is USD; you can use a rate in another currency and interpret the result in that same currency. Fixed charges are excluded.

Water heating

Q = m × c × ΔT, using water density approximately 1 kg/L and specific heat c = 4.186 kJ/(kg·°C). Heating time t = Q ÷ (P × η), with power in kJ/s. Electrical energy equals thermal energy divided by efficiency.

Efficiency is an estimated input, not a measured promise. The model excludes phase changes, ongoing heat loss after heating, tank recovery behavior and altitude effects on boiling point. Target temperature must not be below starting temperature.

Microwave power conversion

P₁ × t₁ ≈ P₂ × t₂. A 1,000 W instruction for 3 minutes becomes approximately 4 minutes 17 seconds at 700 W. Use cooking output wattage, not electrical input power.

This is an energy-equivalence estimate. Food geometry, moisture, containers and microwave distribution affect results. Stir, allow standing time and verify safe internal temperature.

Clean air delivery and air changes

Room volume = length × width × ceiling height. CADR (m³/h) = room volume (m³) × ACH. In customary units, CADR (CFM) = room volume (ft³) × ACH ÷ 60. The inverse formulas give ACH and suitable room area.

One CFM equals 1.69901079552 m³/h. CADR refers to particle removal; it is not outdoor-air ventilation. The model assumes ideal mixing, one open room and operation at the rated fan setting. Select ACH for your circumstances; no single value guarantees health protection.

Sizing and cooking estimates

Cooling, space heating, dehumidification and hot-water storage depend on building conditions and real usage. These tools show rounded ranges and disclose their simplifying assumptions. They do not replace professional load calculations or equipment installation advice.

The air fryer starting rule reduces oven time by 20%, and reduces temperature by about 20°C in metric mode or 25°F in customary mode. These are separate approximate cooking conventions, not equivalent temperature offsets. Optional food and crowding adjustments are empirical.

Units, precision and review

1 foot = 0.3048 meters; 1 US gallon = 3.785411784 liters; °F = °C × 9/5 + 32; 1 kW ≈ 3,412.14 BTU/h. Gallons throughout this site mean US liquid gallons, not UK imperial gallons. Language and unit system are separate controls.

Display rounding matches the method: approximate cooking and sizing use ranges, while energy and dimensional calculations retain useful numerical detail. References support the stated relationship or context; a reference does not endorse every estimated parameter. All languages share one calculation engine.