Water Cooling Efficiency Estimator

The AIO that lost to a $40 air cooler

"I bought a 120mm AIO and my CPU runs hotter than my friend's $40 air cooler." Small AIOs lose to big air coolers because they have less radiator surface area and less thermal mass. AIOs win with 240mm+ and sustained loads where the water mass buffers spikes. The marketing never mentions this — it just shows a sleek pump block and a RGB fan.

The Water Cooling Efficiency Estimator estimates whether your radiator size and fan speed can dissipate your CPU/GPU heat load, and predicts the delta-T over ambient. Avoid the "water cooler cannot hold temps" failure. Runs locally, no signup.

How the tool works

The estimator computes three things:

• Heat load (watts) — CPU or GPU package power under sustained load. Overclocked chips pull more; use the PC Wattage Calculator to estimate.
• Radiator dissipation capacity — based on radiator size (120, 240, 280, 360, 420mm), thickness, fan speed (RPM), and fin density. Roughly 100–150W per 120mm of radiator at moderate fan speed.
• Delta-T over ambient — heat load ÷ dissipation capacity, scaled by fan speed. A 250W CPU on a 240mm radiator at 1500 RPM might run 15–20°C over ambient; the same chip on a 360mm runs 10–12°C.

The tool flags three failure modes:

• Undersized radiator — heat load exceeds dissipation capacity. Temps climb until throttle.
• Insufficient fan speed — fans too slow to move air through the radiator. Temps rise.
• Pump flow restriction — flow too low to carry heat from block to radiator. Rarely the bottleneck above ~1 GPM.

Step-by-step usage

1. Enter your CPU or GPU heat load (watts under sustained load). Estimate with the PC Wattage Calculator if unsure.
2. Enter your radiator size (120, 240, 280, 360, 420mm) and thickness.
3. Enter your fan speed (RPM) and count.
4. Read the dissipation capacity and delta-T. Delta-T over 20°C means undersized.
5. Adjust radiator size or fan speed to hit a target delta-T (under 15°C is comfortable).

Common hardware problems this tool solves

• "My 120mm AIO loses to a $40 air cooler" — small AIOs have less surface area and thermal mass than big air coolers. AIOs win with 240mm+ and sustained loads.
• "My CPU temps climb under sustained load" — radiator cannot dissipate the heat. Upsize the radiator or raise fan speed.
• "My AIO is loud but temps don't improve" — fans are fighting restricted airflow. Check for dust in the radiator or obstructed intake.
• "Custom loop or AIO?" — custom loops win on dissipation (more radiator area, bigger pumps) but cost 3–5× more. AIOs are the value pick for most builders.

For deeper cooling context, browse the CPU fix hub and the Fan Curve Simulator.

Pro tips for water cooling

• Roughly 120mm of radiator per 100–150W of heat. A 240mm handles a stock CPU; a 360mm handles an OC'd CPU or a mid GPU; CPU+GPU loops want 420mm+.
• AIOs win with 240mm+ and sustained loads. Small AIOs (120mm) often lose to big air coolers. The water mass buffers spikes — that is the AIO advantage at scale.
• Push or pull fans? Performance is nearly identical. Push is slightly easier to clean (dust on the rad face); pull is easier to mount. Pick by case fit.
• Flow rate matters marginally above ~1 GPM. Beyond that, more flow gives diminishing returns; restriction and pump noise matter more than raw flow.
• Bleed the loop. Air bubbles reduce dissipation and add pump noise. Tilt the case while filling to chase bubbles out.

Water cooling is radiator sizing, not magic. The estimator exists so you match the radiator to the heat load, not buy an AIO on aesthetics and discover it cannot hold temps.