The golden rule: peak vs continuous
The single most common spec trick is quoting a peak figure that a product can hit for a split second, not the continuous figure it sustains. You will see it on power tools, amplifiers, power stations and motors. Peak numbers look impressive but tell you little about real performance.
Whenever you see a headline number, ask: is this peak/maximum or continuous/rated? The continuous figure — what the device delivers all day — is the one that matters. Reputable spec sheets list both; the most honest products lead with continuous.
Lumens vs watts: brightness vs energy
People still shop for light bulbs by watts, but watts measure energy used, not brightness. Lumens measure brightness. Modern efficient lighting produces far more lumens per watt than old bulbs, so a low-wattage LED can be brighter than a high-wattage incandescent. When buying lighting, compare lumens for brightness and watts only for running cost. Guidance from ENERGY STAR uses lumens for exactly this reason.
mAh and the capacity you never get
Battery and power-bank capacity is quoted in milliamp-hours (mAh), but you never get the full figure as usable energy. Voltage conversion losses mean a power bank typically delivers around 60–70% of its rated mAh to your device. So a 10,000mAh bank gives roughly 1.5–2 phone charges, not the number you might expect. Plan around usable capacity, and remember watt-hours (Wh) is the more honest measure — and the one airlines use.
IP ratings: what 'waterproof' really means
An IP rating (e.g. IP67, IPX7) precisely describes resistance to dust and water, and it is far more reliable than the vague word 'waterproof'. The first digit is dust protection; the second is water. IPX7 survives brief submersion; IPX5–6 handles jets and rain; IPX4 covers splashes. If a digit is shown as 'X', that protection was simply not rated. Match the exact rating to how you will use the product rather than trusting marketing adjectives. The standard is defined internationally by the IEC.
PSI vs GPM, CFM vs MPH: the pairs that mislead
Many products are sold on one half of a pair while the other half does the real work:
- Pressure washers: marketing shouts PSI (pressure), but cleaning speed is PSI × GPM (flow) — the 'Cleaning Units'. A high-PSI, low-flow washer can clean slower than a balanced one.
- Leaf blowers: MPH (air speed) sounds powerful, but CFM (air volume) actually moves the leaves. Prioritise CFM.
When a product leads with the flashier number, check its quieter partner — that is usually where the real performance hides.
Star ratings and 'review' counts
Be skeptical of averaged star ratings and giant review counts, which can be inflated, incentivised or mixed across product variants. A more reliable signal is the content of detailed long-term reviews: look for recurring, specific complaints (a part that fails, a fit issue) rather than the headline average. This is also why, on this site, we never fabricate aggregate ratings — you can read about that in our methodology.