Water Heating · South
Cost to run a tankless water heater in Louisiana
At Louisiana’s average residential rate of 12.87¢ per kWh, a tankless water heater drawing 18000W for 0.5 hours a day, at a 80% duty cycle, costs about $28.21 per 30.44 use days. Change the numbers below to match how you actually use yours.
Tankless Water Heater electricity cost calculator
Use watts and running time, or enter energy from a label, meter or completed load. Your inputs stay on this device.
Enter a number within each field’s limits to calculate your cost.
Your estimated energy cost
2,628 kWh across 365 use days per year
Power mode includes your selected duty cycle. The monthly figure assumes 30.44 use days; the annual total uses your selected use days. These are estimates at the entered rate.
Energy charges only. Fixed utility fees, purchase, installation and maintenance are excluded. See the calculation method and sources.
Why the cost differs in Louisiana
Louisiana has the 2nd cheapest residential electricity of the 50 US states and Washington, DC we track, at 12.87¢ per kWh against a national average of 18.16¢. That is -29.1% compared with the national figure. Louisiana sits next to Gulf Coast natural gas production, which keeps generation costs low even after accounting for the recurring expense of hurricane restoration and grid hardening. Retail service is regulated. The cooling season is long and humid, so air conditioning dominates annual consumption and duty cycles stay high through the night in midsummer.
For this appliance specifically, the difference works out to a saving of $139 a year against what the same tankless water heater would cost at the national average rate. Run the identical appliance in Hawaii and it would cost $1,240 a year; in Nevada it would cost $334. That spread of $906 is entirely down to location.
Reducing use by 100 kWh would save $12.87 in energy charges at Louisiana's average rate, compared with $18.16 at the US average. Whether a replacement appliance pays for itself also depends on its purchase price and the energy it actually saves.
Use the energy and delivery price that applies to your own utility plan in Louisiana. If your plan has time-of-use prices, calculate each period separately or use a rate weighted by the electricity used in each period. Fixed monthly fees are outside this appliance energy-cost estimate.
| Location | Rate | Per month | Per year |
|---|---|---|---|
| Louisiana this page | 12.87¢ | $28.21 | $338 |
| US average | 18.16¢ | $39.80 | $477 |
| Nevada cheapest state | 12.72¢ | $27.88 | $334 |
| Hawaii most expensive | 47.18¢ | $103 | $1,240 |
Louisiana electricity rate trend
Rates in Louisiana have moved from 12.33¢ to 12.87¢ per kWh between September 2025 and August 2026. The national residential average changed +3.4% from the same month a year earlier.
2025-09 to 2026-08 · cents per kWh
About running a tankless water heater
Enormous instantaneous draw but zero standby loss. Whether it saves money depends heavily on household usage patterns and incoming water temperature - cold-climate installations need far more power for the same output temperature.
How we worked this out
The arithmetic is simple and we would rather show it than hide it. Divide watts by 1,000 to get kilowatts, multiply by hours of use and by the duty cycle to get kilowatt-hours, then multiply by your rate:
18000W ÷ 1000 × 0.5h × 80% = 7.200 kWh/day × 12.87¢ = $0.927 per day
One honest caveat: Louisiana’s figure is a state average published by the EIA. Your own utility’s tariff, any time-of-use pricing, fixed monthly service charges and local taxes all shift the real number. Put your actual per-kWh rate into the calculator above for a figure that reflects your bill.
How to estimate your tankless water heater electricity use
An electric tankless heater can have a large input rating because it heats water during use. Its high wattage does not mean it draws that power all day: flow, temperature rise and control settings determine actual draw and runtime.
This calculator covers electric tankless heating. A gas tankless unit needs a fuel-use calculation as well as its smaller electrical load.
- Use the electrical input while hot water is flowing and the total hot-water runtime. The maximum rating may overstate draw when the heater modulates.
- A calculated example of 18 kW for 15 minutes is 4.5 kWh. At an illustrative $0.20/kWh that costs $0.90 for that period.
- Compare storage and tankless systems at equivalent hot-water demand, not just their rated watts.
- Annual EnergyGuide energy or a representative measured period can provide an alternative to estimating each draw of hot water.
Calculation and data sources
Daily kWh = watts ÷ 1,000 × hours × duty cycle ÷ 100. Multiply kWh by your rate in dollars per kWh to get cost. The wattage, hours and duty cycle above are editable example assumptions, not EIA measurements of this appliance.
The US and state average prices come from the EIA for August 2026. A state average is a starting point; your bill is the better source for your tariff.
Questions about tankless water heater running costs
How much electricity does a tankless water heater use?
In this example, 18000 watts at a 80% duty cycle uses 14.400 kWh per scheduled hour. At 0.50 hours per day, that is 7.200 kWh per use day. Your model and operating conditions can differ.
How much does it cost to run a tankless water heater for an hour?
The default example costs $1.853 per scheduled hour at the Louisiana average of 12.87¢/kWh for August 2026. This includes the selected duty cycle. Enter your watts, duty cycle and electricity price for your own estimate.
Does the annual cost assume I use it every day?
The reference tables use 365 days at the stated daily hours; monthly figures use 30.44 days. These are comparison scenarios, not forecasts. For a heater used on 90 days, enter 90 use days per year in the calculator.
Why does electricity running cost vary by state?
For August 2026, the EIA state averages range from 12.72¢/kWh in Nevada to 47.18¢/kWh in Hawaii. Equal electricity use costs more at a higher rate. Your utility tariff can differ from the state average.
Should I enter rated watts or average watts?
Use the input that matches your measurement. Rated watts can represent maximum draw. If you know the average watts over the selected hours, enter that average and set duty cycle to 100%; do not reduce it again for cycling.
Does this include the purchase price?
No. This calculator estimates electricity at the entered usage-based rate. Purchase, installation, maintenance and fixed monthly utility charges are separate.
How do I estimate occasional use?
In watts-and-hours mode, enter the hours used on an active day, then select the number of use-days per year. The monthly figure remains a 30.44-day equivalent at that daily use; the annual figure uses your selected days.