Tools
Two calculators that actually answer the question.
No email wall, no “a specialist will contact you”. The maths is standard and the assumptions are printed under every result, so you can check the working.
Calculator
What size water heater do you need?
Undersize it and you run out mid-shower. Oversize it and you pay to keep water hot that nobody uses. Both answers below come from the standard sizing methods, not a rule of thumb.
Count what gets used in your busiest hour — a weekday morning, most likely. Not the whole day.
Recommended
Your peak-hour demand is 54 gallons, so look for a first hour rating (FHR) of about 54 on the EnergyGuide label.
DOE peak-hour-demand method. Gas recovers faster than electric, so a gas tank hits the same FHR at a smaller size. A specific model’s FHR is on its label and beats this estimate.
Calculator
What is that leak costing you?
A drip you can barely hear runs every second of every day. Here is the year’s worth.
Count for fifteen seconds and multiply by four. Sixty a minute is roughly one drip a second — a tap most people would not bother reporting.
Over a year
About $12 a year at $12 per 1,000 gallons — roughly 3 gallons a day going straight down the drain.
A drip is taken as 0.25 mL, the figure the USGS drip calculator uses. Most utilities bill sewer on metered water volume, so a leak usually costs twice over — change the rate above to match your bill.