About
About WaterHeaterCalc
WaterHeaterCalc exists because water heater sizing is arithmetic that almost nobody does, and the cost of not doing it is buying the wrong appliance and living with it for a decade.
What we actually do
We build calculators from published relations and code tables, and we build reference pages that show the working. There are 16 calculators here. Every one shows its formula, renders a worked example into the page itself so it reads correctly with no scripts running, and labels each figure as either a published standard or a planning convention.
That labeling is the whole point. The DOE Uniform Energy Factor test procedure and "descale it annually" are both useful, but they are not the same kind of statement, and a reader is entitled to know which one they are being handed.
What we do not do
We do not test water heaters in person and we never claim to. Nobody installs forty water heaters to write a roundup, and any site that says it did is telling you a story. What we do instead is read manufacturer specifications, installation manuals, code tables and the consensus of verified owner reviews, and then say plainly where a figure comes from.
We also do not invent numbers. Where a manufacturer does not publish a figure, the page says so. That is why no page here asserts a flow rate at a temperature rise the manufacturer never published, and why the gas pipe calculator refuses propane outright rather than extrapolating from the natural gas table.
The products
The catalog holds 208 products, each one checked against the live Amazon catalog and read against what the page claims about it. A live listing is not a correct listing: searches in this category return swimming pool collectors, RV appliances, hydronic expansion tanks, well pressure tank tees and, in one case, a fly fishing stream thermometer. Every rejection is recorded in the repository with its reason.
What belongs to sister sites
Two adjacent subjects are deliberately not ours. HouseProjectCalc covers what an installation costs. HomeWaterCalc covers softening, filtration and water quality. What scale does to a heat exchanger is ours; whether to treat the water is theirs, and pretending otherwise would give you two half answers instead of one good one.
How this is funded
Affiliate commission on products readers buy through links here, at no extra cost to them. It does not change what we recommend, and the clearest evidence of that is how often these pages tell you to skip something or to buy the cheaper option. Full disclosure here.
Researched guidance, not professional advice. A water heater is a pressure vessel and a gas one is a combustion appliance. The temperature and pressure relief valve is never capped, plugged or removed. Gas line, flue and vent work belongs to a licensed plumber or gas fitter, because improper venting produces carbon monoxide. Water at 140 F scalds a child in seconds.