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How Much Does It Cost to Run a Electric Tankless Water Heater in California? (2026)
Electric tankless heaters draw enormous power, 12 to 36 kW, but only while hot water is flowing. They avoid the standby losses of a tank, saving 10 to 30 percent for most households, but need heavy wiring.
A typical electric tankless water heater (18,000 W) costs $6.30 per hour, or about $141.75 per month at 0.75 hours a day in California. Expensive to run
| Wattage | Per hour | Per day | Per month | Per year |
|---|---|---|---|---|
| Low (12,000 W) | $4.20 | $3.15 | $94.50 | $1,150 |
| Typical (18,000 W) | $6.30 | $4.72 | $141.75 | $1,725 |
| High (36,000 W) | $12.60 | $9.45 | $283.50 | $3,449 |
Formula: watts ÷ 1000 × hours × price per kWh. Typical use is 0.75 h/day ≈ 4,928 kWh per year.
In California, with electricity at $0.35 per kWh (source: EIA Table 5.6.A, 2026-06), a typical electric tankless water heater costs $6.30 per hour and about $1,725 per year at 0.75 hours a day. That is about 94% more than the US national average of $72.90 per month, because electricity in California costs $0.35 per kWh against $0.18 nationally. Each $1.00 of electricity buys roughly 0.2 hours of use.
How to lower the cost of running a electric tankless water heater
- Install low-flow showerheads. Flow rate directly drives power draw.
- Fix hot water drips. Each one fires the heater.
- Set the outlet temperature to 49 C and skip mixing cold water at the tap.
In standby it draws about 2 W, which adds roughly 18 kWh ($6.13) per year if it is never unplugged.
Frequently asked questions
How much does a tankless water heater cost per month?
About 400 kWh a month for a family of four, roughly 10 to 30 percent less than a tank.
Do tankless heaters use a lot of electricity?
A lot at once, but for short periods. Total use is typically lower than a tank.
Do I need a panel upgrade for an electric tankless heater?
Often yes. Whole-house units need 100 amps or more of dedicated capacity.
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Cost by region
- United States (average)
- California
- Texas
- New York
- Florida
- Canada (average)
- United Kingdom
- Germany
- France
- Australia
- India