How We Measure

Wattage measurements

All wall-power measurements come from a P3 International Kill A Watt P4400. It's not a lab instrument, but it's accurate to within ±0.2% of reading at the wattages relevant to homelab equipment (0–500W), which is enough for the conclusions we draw.

Idle measurements are taken after a system has been running for at least 30 minutes, with the OS fully booted, an SSH session connected, all background services running, drives in standby (where supported), no peripherals attached beyond the network cable, and no active workload. We log readings every 10 seconds for at least 5 minutes and report the median.

Load measurements are taken during a sustained 10-minute stress workload appropriate to the device class. For mini PCs and servers, that's stress-ng running on all logical cores. For NAS units, it's a multi-drive sequential read at maximum capable throughput. For switches, it's full port utilization at line rate.

What we don't measure (yet)

We don't currently report power-on inrush, transient spikes during boot, or behavior under thermal stress beyond the 10-minute load window. These are all interesting and we'd like to add them, but they require equipment we don't yet have.

Cost calculations

Annual cost figures use $0.17/kWh as the default, which is approximately the US residential average per recent EIA data. Our Power Calculator lets you substitute your actual rate or pick a state preset. The 5-year totals assume the same rate over the entire period, which is unrealistic but predictable — actual rates have been rising in most US markets and your real 5-year cost is likely 10–20% higher than the calculator shows.

Recommendations

When we recommend a product, our priority order is (1) reliability and longevity in the use case, (2) idle wattage, (3) total cost of ownership over 5 years, (4) noise, (5) price at purchase. That ordering deliberately favors long-term ownership cost over upfront sticker price, which is why we recommend a $269 mini PC over a $150 used server — the mini PC saves you more in year one alone than the server costs.

Where our numbers come from

Each entry in our Idle Power Database is tagged with its source: Measured means we tested the device ourselves. Community means the number comes from forum posts or community testing on ServeTheHome, Level1Techs, r/homelab, or similar — we cross-reference at least two sources before including a community number. Mfr spec means it's from the manufacturer's published specs, which are usually optimistic but in the right ballpark for newer products.

If you find an error or have a measurement that contradicts ours, please send it. We'd rather update the database than be wrong on the internet.