Enter value in kW:
Formula: tons = kW × 0.28434516375082547
In heating, ventilation, air conditioning, and refrigeration (HVACR) engineering, it is common to measure electrical power in kilowatts (kW) and cooling capacity in refrigeration tons (RT). Converting between these units allows engineers, technicians, and facility managers to size equipment accurately, compare different systems, and assess energy performance.
A kilowatt represents one thousand watts of power. Since one watt equals one joule per second,
1 kW = 1,000 J/s
kilowatts quantify the rate at which electrical energy is consumed or delivered by equipment such as compressors, pumps, and fans in HVACR systems.
The term “ton of refrigeration” originated in the 19th century, referring to the amount of heat required to melt one ton (2,000 pounds) of ice over 24 hours. Over time, it became standardized:
1 RT = 12,000 BTU/hr ≈ 3.51685 kW
Here, BTU/hr is the British Thermal Unit per hour. One BTU is the energy needed to raise one pound of water by one degree Fahrenheit.
To convert from kilowatts to refrigeration tons, divide the power value by the kW-per-ton factor:
Refrigeration Tons (RT) = Power (kW) ÷ 3.51685
Conversely, to convert from refrigeration tons to kilowatts:
Power (kW) = Refrigeration Tons × 3.51685
| Unit | Equivalent |
|---|---|
| 1 RT | 3.51685 kW |
| 1 kW | 0.284345 RT |
Determine the measured or rated power in kilowatts (for electrical input) or the capacity in refrigeration tons (for cooling output).
Choose the appropriate formula based on the direction of conversion (kW → RT or RT → kW).
Perform the division or multiplication using the 3.51685 factor.
For practical purposes, round to two decimal places, unless higher precision is required.
Convert 10 kW of compressor power into refrigeration tons:
10 kW ÷ 3.51685 ≈ 2.84 RT
Thus, a 10 kW compressor corresponds to approximately 2.84 refrigeration tons.
Convert 5 RT of air-conditioning capacity into kilowatts:
5 RT × 3.51685 ≈ 17.58 kW
A 5-ton AC unit requires roughly 17.58 kW of cooling power.
HVACR engineers use these conversions when selecting compressors, chillers, and cooling towers to match building load calculations, ensuring neither undersized nor oversized equipment is installed.
Facility managers compare energy consumption (in kW) against cooling delivered (in RT) to compute Coefficient of Performance (COP):
COP = Cooling Output (kW) ÷ Electrical Input (kW)
Here, cooling output is refrigeration tons converted into kW for consistent units.
If cell A2 holds the kW value, use:
=A2 / 3.51685For RT in cell B2 to kW:
=B2 * 3.51685
Identical formulas apply in Google Sheets. Use named ranges for clarity, e.g., =kW / TON_FACTOR.
function kWToRT(kw) {
const factor = 3.51685;
return kw / factor;
}
function rtToKW(rt) {
const factor = 3.51685;
return rt * factor;
}
// Usage
console.log(kWToRT(15)); // ≈4.27 RT
def kw_to_rt(kw):
return kw / 3.51685
def rt_to_kw(rt):
return rt * 3.51685
print(rt_to_kw(3)) # ≈10.55 kW
When reporting results:
The 12,000 BTU/hr definition assumes a standard reference of 32 °F ice–water mixture. In practice, refrigerant properties and ambient conditions can shift actual capacity by a few percent.
Over time, fouling of heat exchangers and refrigerant charge loss reduce actual cooling capacity. Field measurements in kW should be converted back to RT to compare against original specifications.
Mixing up kW-per-ton values (some references use 3.517 or 3.52) can introduce small errors. Always stick to 3.51685 for consistency.
Avoid rounding intermediate results; retain full precision until the final step to minimize cumulative error.
Store the conversion factor as a constant in your code or spreadsheet to ensure uniformity across all calculations.
A: Refrigeration tons remain an industry convention in HVACR, enabling quick comparison of system sizes even when electrical input is measured in kilowatts.
A: Yes. Since 1 BTU/hr ≈ 0.000293071 kW, convert BTU/hr → kW first, then kW → RT if needed:
RT = (BTU/hr × 0.000293071) ÷ 3.51685
A: COP uses kW units for both input and output. To calculate COP from RT ratings, convert tons to kW cooling output then divide by electrical kW input.
An office tower uses a 500 kW chiller. To verify cooling capacity in RT:
500 kW ÷ 3.51685 ≈ 142.18 RT
For redundancy, two chillers of 75 RT each are installed (150 RT total), providing a capacity buffer of 5.82 RT above calculated load.
During a summer audit, measured input dropped to 450 kW under low-load conditions:
450 kW ÷ 3.51685 ≈ 128.0 RT
Indicating that the system operated at roughly 128 RT, matching predicted seasonal load profiles.
Mastering kW ↔ RT conversions is fundamental for HVACR equipment selection, energy analysis, and performance verification. To ensure accuracy and consistency:
With these guidelines, you can confidently convert between kilowatts and refrigeration tons to optimize system design, improve energy efficiency, and perform accurate field assessments.
While Coefficient of Performance (COP) is widely used to gauge refrigeration efficiency, additional indices offer deeper insight into system health and comparative performance across technologies.
EER compares steady-state cooling output to electrical input:
EER = Cooling Capacity (BTU/hr) ÷ Electrical Power Input (W)
Converting kW to RT enables calculation of EER per standard benchmarks:
IPLV assesses part-load performance across four standard operating points. By measuring kW input and RT output at each point, then converting units appropriately, you derive a weighted performance value more representative of real-world conditions.
IPLV = (0.02 × EER100% + 0.617 × EER75% + 0.238 × EER50% + 0.125 × EER25%)
Each EER is calculated after converting kW to RT or kW to BTU/hr, ensuring consistent units.
Beyond installation costs, life-cycle cost (LCC) incorporates energy consumption, maintenance, and eventual replacement. Converting kW to RT at various loads informs predicted energy usage over the equipment’s lifespan.
A 100 kW chiller (≈28.43 RT) running 2,000 hours/year at $0.10/kWh:
Annual Energy = 100 kW × 2,000 h = 200,000 kWh → $20,000/year
Over 15 years, energy cost = $300,000; compare against capital and maintenance to determine total LCC per RT.
Steady-state conversions provide a snapshot, but transient models capture startup behaviors, defrost cycles, and load swings. Converting instantaneous kW readings to RT at high sampling rates yields continuous cooling capacity curves.
For each timestamp:
Rapid startup draws may show 150 kW peaks (≈42.66 RT) before stabilizing at 80 kW (≈22.74 RT). Plotting these curves aids in selecting soft-start drives or adjusting control strategies.
Advanced controllers modulate compressor speed or staging to match load. By continuously converting measured kW to RT, the control algorithm maintains target setpoints with minimal power waste.
VSDs adjust motor speed to modulate refrigerant flow. Converting kW draw in real time to RT informs the controller of actual cooling delivered versus demand, improving part-load efficiency.
BAS platforms aggregate kW, RT, temperature, and humidity data. Converting between units in raw data streams allows unified dashboards, alarms, and trend analytics for operators.
Set high-RT alarms when cooling falls below design capacity: e.g., RT < setpoint RT × 0.95, using converted kW measurements.
Global programs like ENERGY STAR® and AHRI certify equipment efficiency. Test labs measure input kW and output BTU/hr or RT to verify compliance. Consistent unit conversion is indispensable for accurate certification.
Specifies test conditions for water-chilling packages. Laboratories report both kW and RT, requiring precise conversion factors and rounding conventions.
Predictive maintenance algorithms analyze deviations in expected RT output given measured kW input. Training models on historical kW→RT conversion data enhances anomaly detection.
Digital twins replicate physical refrigeration plants. Converting sensor kW to RT populates the virtual model’s cooling capacity parameters, enabling accurate “what-if” scenarios.
Simulate adding a new 50 kW evaporator: in the twin, add 14.21 RT to the load network and evaluate system response.
Emerging refrigerants (e.g., HFO blends) and magnetocaloric systems may redefine the BTU-based ton standard. Research into alternative ton equivalents expressed in kW continues, but the 3.51685 kW/RT baseline remains industry-accepted.
Stay informed of regulatory changes via ASHRAE publications and updates to the Uniform Mechanical Code, which may adjust ton definitions for new refrigerants.
By embedding robust kW to refrigeration ton conversion workflows throughout design, operation, and maintenance, HVACR professionals can optimize energy use, improve comfort, and extend equipment longevity.