About
About WrapCalc Water Heating
Practical water heating calculators and guides: tank size, tankless GPM, recovery, efficiency, running cost, and payback, with every formula shown.
Who this site is for
WrapCalc Water Heating is built for anyone sizing or replacing hot water: homeowners comparing a tank, a tankless unit, or a heat pump water heater, plumbers and installers checking a first-hour rating or a GPM figure, and property managers estimating running cost across a building.
Why it exists
Hot water is one of the easiest home costs to get wrong: too small a tank and you run cold, too large and you pay to keep standing water hot, a tankless unit that cannot keep up on a cold morning, or an efficiency rating that never matches the real bill. Small sizing errors turn into cold showers, callbacks, and revised quotes. This site exists to make those numbers checkable in minutes, with every assumption visible on the page.
What you will find here
- Calculators with visible math: every input, formula, and output is shown, so a result can be verified by hand or against code tables.
- Reference charts and rate baselines: national averages and typical values, always dated, always labeled as starting points rather than local facts.
- Practical guides: worked examples that pair a parameter table with a hand calculation you can reproduce, written so an apprentice can follow and a journeyman can skim.
- A private Workspace: save assumptions and reports for jobs, quotes, and comparisons without exposing client data.
How content is produced and reviewed
Each calculator ships with machine-checked test cases: fixed inputs must reproduce fixed outputs before the tool is published. Rate baselines carry a data year and are reviewed annually against U.S. Energy Information Administration figures. Guides cite their sources and show the full arithmetic of every worked example. When a reader reports an error through Contact, the page is corrected and the correction is noted.
What this site is not
WrapCalc Water Heating is a planning and reference tool. It is not a substitute for the manufacturer installation instructions, the locally adopted plumbing and electrical codes, the authority having jurisdiction, or the judgment of a licensed installer on site. A calculator output is not an approval, a permit, a quote, or a guarantee of performance. Read the Disclosure before relying on any result.
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