Electric Water Heaters
Electric water heaters include resistance tanks, heat-pump tanks and electric tankless models. They share an energy source but have different heating methods and installation requirements. When a quote says electric water heater, ask which technology and exact model it includes.
A conventional resistance tank is often a straightforward candidate when suitable wiring and space already exist. A heat-pump model deserves comparison where air access and drainage can be resolved. Electric tankless needs a careful assessment of output and electrical demand.
Match the technology to the problem
| Technology | Main decision | Evidence to collect |
|---|---|---|
| Resistance storage | Capacity and complete replacement price | First-hour rating, dimensions, supply requirements |
| Heat-pump storage | Installation fit and expected energy use | Air plan, drainage, operating mode and demand profile |
| Electric tankless | Output at the required temperature rise | Flow curve, electrical load assessment and circuit scope |
| Small point-of-use heater | Delivery to a specific fixture | Local demand, mounting space and connection requirements |
For illustration, Rheem's RETEX-18 page identifies an 18 kW electric tankless model with an advertised maximum flow. Model input and maximum flow are separate specifications; neither establishes its suitability for every home's winter conditions. Rheem electric tankless specifications.
Power is different from energy
Kilowatts describe an electrical load at a moment in time. Kilowatt-hours describe energy consumed over time. A high-power appliance used briefly can have different annual use from a lower-power appliance used longer. Do not multiply a heater's nameplate watts by 24 hours per day as if it runs continuously.
An idealized load example shows why tankless assessment matters: 24 kW at 240 volts corresponds to 100 amperes of power divided by voltage, before applying installation rules. This arithmetic is not a circuit-sizing instruction. Have an electrician assess the actual appliance, panel, service and local requirements.
Storage equipment spreads heating over time and uses stored hot water to handle a draw. Its first-hour rating matters more than a watt figure alone. For a heat-pump candidate, assess location and modes before relying on the savings estimate.
Compare full costs and actual rates
Use annual kWh multiplied by your electricity price for a starting running-cost estimate. Test higher and lower demand and, for a hybrid model, more backup heating. Where time-of-use pricing applies, an annual average rate may miss the effect of the operating schedule.
Request separate installed quotes for realistic alternatives. Include any circuits, service work, condensate routing, removal and permits in installation cost. Use the cost calculator to explore installation-budget allowances. Check rebates against the exact heat-pump model before ordering.
Read heat pump versus electric resistance to compare the two storage choices; read gas versus electric if switching fuels. Apply the best water heaters criteria and take a written demand profile to installers so the final installation addresses both capacity and site conditions.