How we score

Every number on WattWise Labs follows the same formula. This page states it in full: what it measures, the one assumption behind it, and what it deliberately does not claim to measure.

The formula

Estimated annual running cost = annual energy use in kilowatt-hours (kWh), as published by ENERGY STAR, multiplied by an electricity price in dollars per kWh. We default every page to the US average residential electricity price of $0.1856/kWh (US Energy Information Administration, July 2026 reference), and the calculator lets you substitute your own local rate.

Worked example: the Magic Chef MCDR740WEF uses 344 kWh a year, so 344 × $0.1856 = about $64/yr. A standard model in its class, using 385 kWh a year, would cost about $71/yr.

In-class running-cost rank

Every model is ranked, cheapest first, against every other model we track in the same appliance class (for example, all refrigerators against refrigerators, not against dishwashers). Rank #1 is the cheapest to run in that class among the models we track.

Size-adjusted efficiency percentile

Raw running cost rewards small appliances, since a smaller refrigerator will almost always use less energy than a larger one regardless of how efficient its compressor is. So alongside running cost, we compute an efficiency percentile that normalizes energy use per unit of capacity (per cubic foot, per place setting, per BTU/hr, and so on, depending on class), then ranks every model in its class on that normalized figure. A 4th-percentile efficiency score does not mean a model is expensive; it means it is inefficient for its size.

What the score does not measure

• Reliability, durability, or repair frequency. We have no service or failure-rate data.
• Purchase price or total cost of ownership beyond electricity (water, installation, financing).
• Real-world usage. The federal test cycle behind ENERGY STAR figures is standardized; your climate, settings and habits will move your actual bill up or down.
• Build quality, features, or anything reviewers typically call "best."

An honest note on the word "Labs"

WattWise Labs is a data-analysis operation, not a physical testing lab. Every figure here is computed from ENERGY STAR's published federal certification data. We do not plug in, run, or physically measure appliances ourselves. Where a class has a published "percent less energy than the US federal standard model" figure, we show it directly from the source rather than estimating it.

The source

All energy figures come from ENERGY STAR Product Finder, United States federal government public-domain data. ENERGY STAR data as of July 2026. See the full dataset page for coverage and counts by category.

Who produces this, and how we keep it accurate

WattWise Labs is produced by the data team at Mine Marketing LTD, the publisher named in our terms and privacy policy. It is an independent publication, not affiliated with or endorsed by the U.S. Environmental Protection Agency, the U.S. Department of Energy, or any appliance manufacturer, and we take no payment to raise or lower any model's ranking.

Our editorial standard is single and strict: every figure on the site must trace back to a specific published ENERGY STAR record, and nothing is hand-edited to look better. Rankings and percentiles are generated by the formula above, applied identically to every model. When a reader reports a correction, we re-check it against the ENERGY STAR Product Finder before changing anything, and we refresh the whole dataset as ENERGY STAR updates its certified-product lists (current snapshot: July 2026). Where we lack data, such as reliability or purchase price, we say so plainly rather than filling the gap with a guess. Corrections and questions go to our contact page.