KeepCold Backup Refrigerator and freezer planning

Staging copy: search engines are asked not to index this deployment. Canonical base for this build: https://keepcold-backup.pages.dev

How We Calculate and Compare

The calculator is a planning model. It is not a measurement of your refrigerator and not a measurement of a battery. The same function renders the worked example on the calculator page and the numbers below, so the article cannot drift from the code.

Equations

Average watts from an EnergyGuide-style yearly total:

average watts = annual kWh × 1000 / 8760

Average watts from a compressor duty cycle:

average watts = running watts × duty-cycle fraction

Idle is an AC-equivalent allowance, added before inverter loss. It is not applied a second time:

AC-equivalent watts = average watts + idle watts

Runtime and the capacity a duration needs:

runtime hours = capacity Wh × efficiency × (1 − reserve) / AC-equivalent watts

minimum Wh = duration hours × AC-equivalent watts / (efficiency × (1 − reserve))

Defaults are efficiency 0.85, reserve 0.10, and idle 10 W, so runtime = capacity × 0.85 × 0.90 / (average watts + 10). You can change them in the calculator. Efficiency must stay above zero. Reserve must stay below 1. Those two limits are what keep the divisions defined. A zero or negative energy input is rejected instead of being turned into an infinite runtime.

Worked example

500 kWh/year for 24 hours against 2,048 Wh:

  • Average watts: 57.0776
  • AC-equivalent watts (average + 10 W idle): 67.0776
  • Runtime: 23.3568 hours exactly. Rounded to one decimal, about 23.4 hours.
  • Minimum capacity: 2,104.4 Wh

The 2,048 Wh figure is 56.4 Wh under that minimum, so it does not cover the full 24 hours. The comparison tables use the one-decimal runtime, about 23.4 hours, and do not round it to 24.

A battery-side idle placement is not used

Adding the 10 W after dividing appliance watts by efficiency would treat idle as already on the battery side. This calculator does not do that. For the same 500 kWh example that unused placement is 23.8911 hours and 2,057.3373 Wh. The pages and the result tables stay on the AC-equivalent allowance above.

How the four batteries are ordered

Ascending capacity is the order of the catalog itself: 1,024 Wh, 1,070 Wh, 2,042 Wh, then 2,048 Wh. After you calculate, suitability order puts models that meet the watt-hour plan first, smallest capacity first. If you entered startup watts, a model whose published surge is below that figure is placed after models that are not over the surge figure. You can switch the result table back to capacity order. Neither order is a recommendation to buy, and neither order means the compressor will start.

What is refused

  • No claim that an energy fit means the refrigerator will run.
  • No startup comparison when startup watts were left blank.
  • No use of average watts or annual kWh as if they were continuous running watts.
  • No price, stock, star rating, or testimonial.
  • No automatic rewrite of these pages when a manufacturer URL changes. The weekly check only flags the change.

Real efficiency, idle draw, battery age, state of charge, and room temperature will differ from the defaults. Duty cycle is not a fixed property of a freezer. The content boundary for the site is the Google Search spam policies: the pages that exist are the ones that answer a planning question, not extra doorway URLs.