Every page carries an evidence label

The label at the top of a page tells you what kind of work sits behind it. There are four, and we do not blur them.

Illustrative calculation
Uses the formula shown on the page with example inputs. It is not a measurement of your appliance or your tariff.
Sourced guide
Based on manufacturer documents and official guidance cited on the page. Bill examples are synthetic unless stated.
Research comparison
Compared from manufacturer documents and matched Amazon listings. We have not tested these products ourselves yet.
Field report
Based on our own recorded measurements or installation, with dates, conditions and limits stated. None exist yet. When we run a measurement or an installation trial, it will be published with its protocol, dates and limits, including results that show no saving.

Which sources we trust, in order

  1. The manufacturer's own manual or specification for the exact model and pack, read directly, not summarised from a retailer.
  2. Official guidance from bodies such as the CPSC, EPA and university extension services for safety and method.
  3. The current US retail listing, used only to confirm identity: model number, pack contents and ASIN. A listing does not prove price, stock, safety or quality.
  4. Our own measurements, when they exist, with the meter, duration and conditions stated.

Marketing copy, review counts and star ratings are not sources. We do not quote them, and we do not invent accuracy scores or savings percentages to fill a table.

How products are chosen

A product appears only when we have matched the exact US variant to a manufacturer record. If the pack on Amazon does not match the document we read, the product is either held back or shown with the gap marked "Not yet verified". We look for: fit for the stated job, documented capability, usable coverage or pack size, installation burden, and running cost. Commission rate is not a criterion.

We prefer single units where one is enough. Recommending a four-pack to someone who needs one measurement would raise the order value and lower the usefulness, and we are not doing that.

How the calculator works

The electricity cost calculator uses one formula: watts ÷ 1,000 × hours per day × days × your rate per kWh, or measured kWh ÷ measured days × days × rate. It prints that arithmetic under every result. It never assumes a local tariff; the example rate is labeled and you are asked to replace it. Fixed charges are kept separate because cutting usage does not remove them. There is one implementation of the formula on the site, with a version number, so a worked example on one page cannot disagree with the tool on another.

What savings claims we will not make

  • No percentage saving for a window kit, curtain or power strip unless it comes from a measurement we can show.
  • No "damage-free" promise for tape on your particular paint or finish. We describe a patch test instead.
  • No claim that buying a monitor saves money. A monitor tells you a number; what you do with it is what saves money, if anything.

Dates and corrections

Each guide shows when its sources were last checked. That date changes only when someone actually rechecks the sources, not when the site is rebuilt. Corrections are made in one central record so every page using the fact updates together. Report a problem.