Use published BTU/h as the primary cooling-capacity number and keep rating conditions attached to it.
1. What HP tells you
Horsepower is a machinery class, not a universal refrigeration-capacity conversion. Compressor, refrigerant, heat exchanger and rating method differ by product.
2. What BTU/h tells you
BTU/h maps directly to heat-removal rate. That makes it more useful for a water-cooling problem, but it still must be interpreted under its rating conditions.
3. Real examples
| Model | Nominal HP | Published BTU/h |
|---|---|---|
| Active Aqua AACH50HP | 1/2 HP | 4,020 |
| Penguin Standard | 1/2 HP | 5,000 |
| Penguin High Efficiency | 1/2 HP | 5,750 |
Those are meaningfully different outputs behind the same nominal HP label.
4. Rating conditions matter
Active Aqua publishes both BTU test conditions and separate performance-chart conditions. Its manual explicitly says refrigeration efficiency depends on ambient, installation, heat sources, pump and connecting parts. That is why a sourced BTU plus a rating note is better data than HP alone.
5. How to compare chillers
- BTU/h and test/rating note.
- Minimum/maximum flow.
- Operating water range.
- Indoor/outdoor rating.
- Electrical input.
- Connections and service support.
- Independent evidence from similar setups.
Primary technical references
Run your exact setup
Use your real tub, temperature, ambient, exposure, pump, filter and plumbing. ChillSizer checks thermal capacity and real operating flow together.
Open the System Designer