Disclaimer

The calculators and content on WaterHeaterCalcs.com are provided for general information and planning.

Estimates and sizing/energy guides, not guarantees

Results are deterministic estimates from your inputs, your prices and standard reference conventions (BTU = gallons × 8.33 × ΔT; recovery = input × efficiency ÷ (8.33 × ΔT); FHR = usable storage + recovery; annual kWh/therms = daily gallons × 365 × 8.33 × ΔT ÷ conversion ÷ UEF; cost = parts/unit + labor + add-ons, ×(1 + contingency)). Real units and installs vary — verify measurements and figures before relying on them.

Not a bid, not a price or rate index

Cost tools give planning estimates from your own prices, energy tools from your own $/kWh and $/therm, not bids or contracts, and we store no live utility rate, no equipment or labor price list, no regional cost index, no product catalog and no plumber directory. Cost bands are a labeled sanity guide only. Get itemized written quotes from licensed, insured plumbers.

Confirm on the EnergyGuide label; size up

Sizing and energy tools give planning guides. Confirm your unit’s rated First-Hour Rating, GPM and UEF on its EnergyGuide label and follow the manufacturer’s instructions, and round sizing up and leave headroom for peak demand — real hot-water use, incoming water temperature, recovery and efficiency vary by household, unit, fuel and region.

Labeled typicals, not a certified spec

The DOE hot-water use, gallons + FHR by household, UEF, lifespan, inlet temperature and cost bands are labeled published snapshots / planning typicals — confirm against the EnergyGuide label, the manufacturer’s instructions, local code and a licensed, insured plumber. Water-heater installation, gas, venting, combustion, the temperature-&-pressure relief valve, and the scald / Legionella tradeoff of a temperature setting are a licensed plumber / gas fitter, manufacturer-instruction and local-code matter — not engineered here, and the 120 °F reference is not a medical verdict.

Anti-overlap: residential water-heater sizing, energy & cost only

This site covers residential water-heater / domestic-hot-water sizing, energy-cost, repair & replacement math only — the appliance. It is not a general plumbing / repiping / pipe-sizing / water-pressure / drain-waste-vent resource (pipecalcs owns interior plumbing — the appliance and hot-water sizing only, never the pipe network); not a space heating / furnace / boiler / hydronic / HVAC-load resource (climatecalcs owns space conditioning — a heat-pump water heater is a domestic-hot-water appliance, never a space-heating load); not a solar PV array-sizing resource (wattcalcs — a solar thermal water heater is a cost / type line only); not an attic / wall thermal insulation R-value resource (insulationcalcs — a water-heater blanket is a maintenance line only); not a water treatment / softener / well / septic resource (septiccalcs — heating water only); and not a professional combustion / gas-line / venting / carbon-monoxide diagnosis or code-certification tool.

Not an installation or safety guide

Nothing here is an installation procedure, a gas / combustion / venting verdict, a temperature-&-pressure relief or medical scald / Legionella determination, or safety advice. Defer the professional job to a licensed, insured plumber / gas fitter, follow the manufacturer’s installation instructions, and confirm code with your local building department.