What Size Water Heater Do I Need? A Berks County Answer

Size your new water heater by its first hour rating, not its gallons. The first hour rating is the hot water it delivers in one hour starting with a full tank, and you match it to the most hot water your house uses in any one hour, usually the morning. Six in ten Berks households are one or two people, and a two-person morning adds up to about 45 gallons on the worksheet below, so a standard 40-gallon gas tank covers it with room to spare. A family of four or five needs the five-minute math.

Any plumber on the county plumbers page will ask you "40 or 50?" once you call, and the way to answer is to add up your busiest hour and ask for a first hour rating that covers it, because two 40-gallon tanks can deliver different amounts of hot water in that hour.

The number that sizes a water heater is the first hour rating, not the gallons.

The first shower pulls hot water out of the tank while cold water comes in behind it, and the burner or the heating element starts warming that new water. So the hot water you get in that hour is the tank you started with plus whatever the heater reheats while you're using it, and that's the first hour rating.

The rating depends on the tank size, the fuel, and the size of the burner or the element. Gas burners are rated in BTU, the burner's gas input, and a bigger burner reheats faster. An electric tank reheats slowly, so its first hour rating is mostly what's already in the tank, which is why electric needs more gallons than gas for the same busy hour. The rating is printed on the yellow energy label of every new standard tank water heater; buy one whose rating is at least your busiest hour.

Add up your busiest hour with the worksheet.

Your busiest hour is usually the morning, unless the dishwasher and washer run after dinner while someone showers.

Count each use in your busiest hour, multiply by its gallons, and add them up; the total is the first hour rating to shop for.

The example that comes with the worksheet is three showers, one shave, and one round of dishes by hand, which comes to 66 gallons, so that household wants a rating of 66 or more. For a couple who both shower, one shaves, and someone rinses the breakfast dishes, it's 20 plus 20 plus 2 plus 3, which is 45.

A 40 versus a 50 gallon water heater: what each one delivers in an hour.

Here are first hour ratings from two makers' standard residential lines, one range per size; the label on the model in front of you is the number that counts, not this table.

On one maker's sheet, a 40-gallon tank with a 40,000 BTU burner delivers 84 gallons in the first hour. The same maker's 50-gallon tank with a 38,000 BTU burner delivers 85. The 40 with the bigger burner and the 50 with the smaller one give you the same hour of hot water. The burner moves the number as much as the tank does.

Electric is different. With the same 4,500 watt elements, a 40 delivers 55 gallons, a 50 delivers 57 to 63, and a 55 delivers 72. Past that, on electric, the choices are the 80-gallon heat pump unit, which delivers 86 in the first hour, or spreading the showers over more than one hour. Whether a heat pump unit fits your house is in our post on what a water heater replacement costs in Berks.

The price step is small. As of 2026, the same-line 40- and 50-gallon gas tanks list at $799.99 and $819.99, a $20 difference, and the same-line electric tanks at $509.99 and $589.99, an $80 difference. Installed, and nationally, a 40-gallon replacement runs about $800 to $2,300 and a 50 about $800 to $2,500. Going up one size is cheap. Going up to a 75-gallon tank with a large burner isn't: it installs at about $1,100 to $4,000 and brings its own questions of fuel and space.

What a Berks house does and doesn't change about the answer.

A rowhome in Reading, a ranch in Spring Township and a farmhouse out past Oley don't each need a different tank. The house doesn't set the gallons; the people in it and their busiest hour do. The house sets the fuel, the space, and how cold the water comes in.

Fuel comes first. Gas reheats faster and gives a higher rating per gallon of tank; an electric heater needs a bigger tank to cover the same morning. Which fuel or type to buy, and what the job costs here, is in our post on what a water heater replacement costs in Berks.

Space surprises people. A maker asks for 24 inches clear in front of the unit and a floor that carries a full tank, and a standard 50-gallon gas tank is about 57 inches tall and 22 across. A crawlspace or a low basement ceiling might force a short model, the kind a plumber calls a lowboy, and short tanks come in the smaller sizes too: a 30-gallon short gas unit delivers 51 to 65.

The third thing is the incoming water. The standard sizing assumption is 50 degrees coming in, unless you know otherwise. Incoming water is colder in winter than in summer wherever it comes from, and on a well the swing is small (the county's well samples sit in the low to mid 50s all year). So 50 degrees is a fair starting point here. If your tally sits between two sizes, a thermometer under the cold tap in January is the check.

The county has about 163,000 households: 27 percent are one person, 33 percent two, 17 percent three, 13 percent four, and 10 percent five or more. The average is 2.57 people, higher in Reading at 2.78 and lower in Wyomissing at 2.16. A tank that covers two people's busiest hour is sized for the typical Berks house; a family of four or five is the one that needs the worksheet.

Why an undersized or oversized tank costs you money.

An undersized tank runs out. The oversized tank is the quieter mistake: it costs more to buy and more to run, because a tank loses heat to the room around it all day whether or not anyone runs a tap, and burns fuel to replace it.

The thermostat is the other place a tank's running cost hides. Most households need 120 degrees and no more. Set at 120 instead of 140, a tank saves $36 to $61 a year in heat lost to the room, and scale builds more slowly; 140 degree water can scald in under five seconds.

Storage water heaters last 10 to 15 years, so size for the house you'll have over the next decade: a baby on the way, a teenager, or a second bathroom in the plans.

How sizing changes for a tankless water heater.

A tankless heater is sized by flow, in gallons a minute, and by how many degrees it has to raise the incoming water. Add up every hot fixture you'd run at the same time: a standard showerhead is 2.5 gallons a minute, a faucet 2.2, a low-flow showerhead 2.0 and a low-flow bathroom faucet 1.5. Then subtract the incoming temperature from 120, which at 50 degrees in is a 70 degree rise.

A typical gas tankless delivers that rise at 5 gallons a minute, an electric one at about 2. Two showers at once is 5 gallons a minute, a gas unit's whole output and beyond an electric one's. Whether tankless is worth the money for your house is in our post on what a water heater replacement costs in Berks.

Frequently asked questions about water heater size.

What size water heater does a family of four need?

About 89 on the worksheet if all four shower in the same hour plus a shave and the dishwasher. That's above every standard 40- and 50-gallon gas tank in the table (the highest 50 delivers 85) and beyond any standard electric tank. The answers are staggering the showers across more than one hour, or a 75-gallon gas tank with the large burner (125). On electric, even the 80-gallon heat pump unit (86) falls short of 89, so stagger the showers.

How do I find out what size water heater I have now?

The model number is on the data plate on the front of the unit, and the maker's spec page for that model gives the gallons and the first hour rating; the yellow energy label carries the rating too, if it's still on the tank. Write both numbers down with your worksheet tally before anyone quotes you.

Does winter change how much hot water I get?

Yes. Colder incoming water takes longer to heat, so a tank that's just big enough in July runs out faster in January. If you're on the edge between two sizes, winter is the reason to go up.

Before you answer the plumber, write down the gallon rating and the first hour rating of the heater you have now, add up your busiest hour, and carry both numbers into the conversation. A quote for "a 50" with no first hour rating on it is a quote for a tank size, not for hot water. Then pick two or three plumbers from the county plumbers page, get your quotes the way our plumber hiring guide lays out, and buy the heater whose label beats your tally.