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Quick answer from a licensed plumber: Use the wattage printed on your water heater’s rating plate. A. O. Smith says a replacement element must be the same voltage and “no greater wattage” than the rating plate. A 5500-watt element heats about 5 gallons an hour more than a 4500 at an 80°F rise, but it draws about 4 more amps, and Rheem’s wiring guide puts a 5500-watt heater on a 30-amp breaker instead of 25. If the plate says 4500, buy 4500.
Rating plate says 240 V, 4500 W? Rheem’s own screw-in replacement: see the Rheem SP10869MM on Amazon
4500 vs 5500 Watts by the Numbers
Rheem’s element bulletin lists what each common 240-volt element draws and how much water it heats. At an 80°F temperature rise:
| Element (240 V) | Amps | Cold resistance | Recovery at 80°F rise | Rheem breaker / copper wire (240 V heater) |
|---|---|---|---|---|
| 3500 W | 14.6 A | 16.5 Ω | 18 gal/hr | — |
| 4000 W | 16.7 A | 14.4 Ω | 21 gal/hr | 25 A / 10 AWG |
| 4500 W | 18.8 A | 12.8 Ω | 23 gal/hr | 25 A / 10 AWG |
| 5000 W | 20.8 A | 11.5 Ω | 26 gal/hr | 30 A / 10 AWG |
| 5500 W | 22.9 A | 10.5 Ω | 28 gal/hr | 30 A / 10 AWG |
| 6000 W | 25.0 A | 9.6 Ω | 31 gal/hr | 35 A / 8 AWG |
A. O. Smith’s own recovery table agrees within rounding: 23.1 gallons an hour for 4.5 kW and 28.2 for 5.5 kW at an 80°F rise. So a 5500-watt element heats about 5 more gallons an hour. It also pulls about 4 more amps, and Rheem’s wiring guide moves a 5500-watt heater up to a 30-amp breaker.
Why You Match the Rating Plate Instead of Upsizing
A. O. Smith puts the rule plainly in its point-of-use heater manual: “Replacement elements must (1) be the same voltage and (2) no greater wattage than listed on the model rating plate affixed to the water heater.” Rheem says the heater’s “voltage requirements and wattage load” are on the rating plate on the front of the tank, and it sizes the breaker and wire from that wattage. A bigger element on the same circuit asks the breaker and wire for current they were not sized for.
Where to Find Your Wattage
- The rating plate. A. O. Smith: “Check your water heater’s data plate for the correct wattage and voltage.”
- The parts list. Bradford White’s electric parts list, for example, gives its RE240S, RE250S, RE330S, RE340S, RE350S and RE340R models a “Heating Element 240V 4500W” and points to a chart for “other voltage and wattage combinations.”
- Both elements. On a standard two-element heater, Rheem says “only one of the heating elements may heat at a time,” with the upper thermostat in control. Buy the wattage the rating plate lists for each element.
A technician can also read an element’s cold resistance with the power off and the wires disconnected: about 12.8 ohms for 4500 watts and 10.5 ohms for 5500 watts at 240 volts, per Rheem. State’s service handbook notes readings “may vary by up to 7.5%.” On 208-volt power the same elements put out less; our 240V vs 208V element guide has Rheem’s numbers.
Same Wattage, Different Element: Watt Density and Shape
Once the wattage matches, you still choose the element style. The screw-in elements below all use the common 1-inch NPSM thread, per their listings, but they differ in how hard they work each square inch of sheath:
| Element | Watt density (listing) | Shape and length (listing) | At 208 V (listing) |
|---|---|---|---|
| Rheem SP10869MM, 4500 W | LWD (low), stainless | fold back, 13.44″ | 3380 W |
| Rheem SP10552MH, 4500 W | HWD (high), 208 W/sq in, copper | straight, 13.50″ | 3380 W |
| Rheem SP10869PH, 5500 W | MWD, 113 W/sq in, stainless | fold back, 13.47″ | 4130 W |
| Rheem SP10552PH, 5500 W | MWD, 137 W/sq in, copper | fold back, 13.53″ | 4130 W |
| Camco 02583, 4500 W | LWD | fold back; “minimum tank diameter of 13-inches” | not listed |
Camco’s listing says its low-watt-density element “reduces lime deposit buildup when used in areas with hard water.” Rheem’s failure bulletin explains why that matters: scale thicker than 1/16 inch “will reduce the effectiveness of the heating element,” and “softened water can also cause scaling.” Long fold-back elements also need room inside the tank; Bradford White’s copper-element chart lists its 3500-watt-and-up elements for “14″ Diameter tanks and above.”
I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.
What to Buy
Pick the wattage on your rating plate, then the style:
- 4500 W, low watt density: Rheem SP10869MM 240 V / 4500 W, sold by Amazon.
- 4500 W, low watt density (Camco): Camco 02583 240 V / 4500 W, sold by Amazon.
- 4500 W, high watt density, copper, straight: Rheem SP10552MH 240 V / 4500 W, sold by Amazon.
- 5500 W (only if your rating plate says 5500): Rheem SP10869PH 240 V / 5500 W or Rheem SP10552PH, both sold by Amazon.
Parts You’ll Also Need
For the swap itself (Camco’s listing says its element comes with a rubber gasket, and A. O. Smith says “A new gasket must be used in all cases”):
- Camco 09883 element wrench, sold by Amazon. Its listing says it “Fits 1-1/2″ hex on residential screw-in water heater elements.” A. O. Smith warns that regular 1-1/2 inch sockets “are often beveled and may slip.”
- Klein Tools NCVT3P non-contact voltage tester, sold by Amazon. A. O. Smith’s steps say to check the power wires with a non-contact tester after turning the breaker off.
Refill before power: A. O. Smith says power to a tank that is not completely full “will cause the upper heating element to burn out.” Our element replacement guide covers which element failed.
When to Call a Licensed Pro
- You want a different wattage than the rating plate lists. That is a circuit question for a licensed electrician.
- The breaker trips, or you see scorched wires or a melted terminal cover.
- The heater may have taken a lightning strike. Rheem says that if a heater “was involved in a lightning strike, all thermostats and elements should be replaced.”
FAQ
Can I replace a 4500 watt element with a 5500 watt element?
Not unless the rating plate lists 5500 watts. A. O. Smith says replacement elements must be the same voltage and no greater wattage than the rating plate. Rheem sizes a 5500-watt heater for a 30-amp breaker instead of 25.
How much faster does a 5500 watt element heat water?
Rheem lists 23 gallons per hour for 4500 watts and 28 for 5500 watts at an 80°F rise. A. O. Smith’s table gives 23.1 and 28.2.
How many amps does a 4500 watt water heater element draw?
About 18.8 amps at 240 volts, per Rheem. A 5500-watt element draws about 22.9 amps.
What size breaker does a 4500 watt water heater need?
Rheem’s guide lists a 25-amp breaker and 10 AWG copper wire for a 4500-watt heater at 240 volts, and 30 amps with 10 AWG for 5500 watts. Check local electrical codes.
What is a low watt density element?
An element that spreads its wattage over more sheath area. The Amazon listing for Rheem’s SP10869MM calls it low watt density, and Camco’s listing says its low-watt-density element reduces lime deposit buildup in hard water.
Why Trust Plumbing Picks
Plumbing Picks is written by a licensed Georgia journeyman plumber. Every part number, size, rating and fit on this page comes from the manufacturer pages and documents listed below, which we opened and read, or, where the page says so, from an Amazon listing; none of it comes from hands-on testing. Each linked product was shipped or sold by Amazon, new and in stock, when we checked on September 24, 2026. Where a link goes to Amazon we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.
Sources
- Rheem Technical Service Bulletin 1305: Heating Element Properties (voltage, amps, ohms, recovery, circuit breaker)
- Rheem Technical Service Bulletin 1315: Non Simultaneous Operation, Double Element Water Heaters
- Rheem Technical Service Bulletin 1308: Electric Water Heater Element Failures
- Rheem: Residential electric Use & Care Manual AP23124 (branch circuit and wire size guide)
- A. O. Smith: Residential Electric Element Availability Sheet AOSTD63000 (recovery table)
- A. O. Smith: residential electric 120-volt point-of-use manual 185834-000
- A. O. Smith: Residential Electric Water Heater Installation Instructions and Use & Care Guide (March 2021)
- Bradford White: Residential Electric Replacement Parts List 238-51382-00AA (July 2025)
- State Water Heaters: Residential Electric Water Heater Service Handbook (STC082, 2004)
Bottom Line
Match the rating plate: same voltage, no more wattage. 4500 watts is 18.8 amps and 23 gallons an hour at an 80°F rise; 5500 watts is 22.9 amps and 28 gallons an hour, on a bigger breaker. Choose low watt density if you have hard water and room in the tank.