COP / EER calculator
Solve for capacity, electrical power input or COP from the other two, convert to EER and kW/ton, compare against the theoretical Carnot ceiling for your evaporating/condensing temperatures, and estimate annual running cost and CO₂.
How to use this calculator
- Choose the operating mode and what to solve for — capacity, power input or COP.
- Enter the two known values.
- Enter the evaporating and condensing temperatures for the Carnot comparison.
- Optional: add operating hours and electricity price for an annual cost estimate.
- Read COP, EER, kW/ton and the Carnot ceiling.
What this calculates
Coefficient of Performance (COP) is the exact ratio of useful heating or cooling output to electrical power input — not an approximation, so any one of the three quantities follows directly from the other two:
COP = Q̇ / Ṗ
Q̇ = capacity (cooling or heating output), kW
Ṗ = electrical power input, kW
COP = coefficient of performance, dimensionless
EER (Btu/(h·W)) = COP × 3.412142
kW/ton = 3.51685 / COP
EER and kW/ton aren't independent figures — they're exact unit conversions of the same COP, included because different parts of the industry quote different ones. Choose which of the three quantities to solve for with the "Solve for" dropdown; the other two become the inputs.
The Carnot ceiling
No refrigeration or heat-pump cycle operating between two fixed temperatures can beat the reversed-Carnot-cycle COP for those temperatures — this is second-law thermodynamics, true for any refrigerant, any compressor, any real cycle. In kelvin (Tc = evaporating, Th = condensing):
COP_Carnot,cooling = T_c / (T_h − T_c)
COP_Carnot,heating = T_h / (T_h − T_c)
Your actual COP shown as a percentage of this ceiling is a genuine second-law (exergy) efficiency — a well-designed real system might reach roughly 40–60% of Carnot, though that range is a rough orientation, not a target this tool checks you against. This deliberately stops short of simulating an actual refrigerant cycle (which needs real enthalpy data from a specific refrigerant's equation of state) — the same limitation noted on the Refrigerant Pipe Pressure Drop Calculator, where typical refrigerant properties are offered as rough starting points for the same reason.
Heat rejected / absorbed on the other side
A first-law energy balance across the cycle gives the flow on the other side for free: in cooling mode, the condenser rejects the cooling capacity plus the electrical power input; in heating mode, the source side absorbs the heating capacity minus the electrical power input. This is idealised — it assumes all electrical input ends up as either useful output or heat, ignoring motor and mechanical losses — close enough for a sizing sanity check, not a substitute for the equipment manufacturer's own figures.
Running cost and CO₂
The optional running-cost section is plain arithmetic (power × hours = annual energy; energy × price = annual cost). The CO₂ estimate reuses the same grid carbon-intensity data and transmission-loss-adjusted calculation as the Electricity Carbon Footprint Calculator — see that tool for the data source and its limitations (a location-based grid average, not an audited emissions factor).