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HVAC Energy Efficiency Calculator

Reference: AHRI 550/590 / ASHRAE 90.1

⚡ HVAC

Free HVAC efficiency calculator. Find chiller/AC COP and EER from cooling capacity and input power, and estimate annual energy use and running cost from operating hours and tariff.

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📋 ASSUMPTIONS & BASIS

AHRI 550/590 / ASHRAE 90.1

Design criteria, governing codes and assumptions.

ℹ About This Calculator

Cooling plant efficiency decides a large share of a building energy bill. This calculator finds the coefficient of performance (COP) and energy efficiency ratio (EER) from the cooling capacity and the rated input power, converts to the familiar kW-per-TR figure, and estimates the annual energy use and running cost from the operating hours, load profile and electricity tariff, so you can compare equipment and justify efficiency upgrades.

A single full-load rating understates real performance because plant spends most of its life at part load, where good chillers are more efficient — hence part-load metrics like IPLV/NPLV and a load-weighted estimate. COP, EER and kW/TR are just different ways of expressing the same ratio. Use consistent (net) capacity and input power, include auxiliaries where relevant, and confirm ratings to AHRI 550/590 and minimum efficiencies to ASHRAE 90.1 or the local energy code.

Efficiency & Annual Energy Method

AHRI 550/590 / ASHRAE 90.1

Step 1 - COP = cooling capacity (kW) / input power (kW).
Step 2 - EER = COP x 3.412 (Btu/h per W); kW/TR = 3.517 / COP.
Step 3 - Weight input power by the load profile (share of hours at full and part load).
Step 4 - Annual energy = effective input power x operating hours per year (kWh).
Step 5 - Annual cost = annual energy x electricity tariff.

Worked Example

A chiller gives 350 kW cooling for 62 kW input. COP = 350 / 62 = 5.65, EER = 19.3, kW/TR = 0.62. Running 3,000 hours a year at a load-weighted 55 kW input uses 165,000 kWh; at a 0.12 tariff that is about 19,800 per year.

Efficiency & Running Cost Notes

Rate on the same basis

When comparing equipment, use net capacity and input power measured to the same standard and conditions. Small differences in test conditions or whether auxiliaries are included can swamp the real efficiency difference.

Part load is where the savings are

Because plant runs mostly at part load, part-load efficiency (IPLV/NPLV) and a load-weighted estimate usually matter more than the peak rating. Variable-speed compressors and pumps improve part-load performance markedly.

Payback

The annual-cost output lets you compare a higher-efficiency unit against its price premium and estimate a simple payback — often the deciding factor once the energy code minimum is met.

Frequently Asked Questions

What is the difference between COP, EER and kW/TR? +

They all express the same efficiency. COP is cooling output divided by electrical input (both in watts). EER is COP times 3.412. kW/TR is 3.517 divided by COP — lower kW/TR means a more efficient chiller.

Why weight by part load? +

Plant runs at full load for only a small fraction of the year, so a load-weighted or IPLV figure reflects real energy use far better than the full-load rating alone.

How do I estimate annual running cost? +

Multiply the effective input power by the annual operating hours to get kWh, then multiply by the electricity tariff. Include pumps and fans if you want plant-level cost.

What is a good chiller efficiency? +

It depends on type and size, but lower kW/TR (higher COP) is better. Compare candidates on the same basis and against the minimum required by the energy code.

Which standard governs the ratings? +

Chiller performance is rated to AHRI 550/590, and minimum efficiencies are set by ASHRAE 90.1 or the local energy code.