Should You Install an Electric Tankless Water Heater?
We get asked about electric tankless water heaters fairly often, especially by homeowners who want to get away from gas but still like the idea of tankless.
For a whole-house system, our answer is usually:
Probably not.
The problem is not that electric tankless water heaters do not work.
The problem is how much electricity they need.
Whole-house electric tankless uses a huge amount of power
Heating water instantly takes a tremendous amount of energy.
A typical whole-house electric tankless unit can draw 80, 100, 120 amps or even more when operating.
For comparison, many Bay Area homes only have a 100-amp or 200-amp electrical service for the entire house.
Some larger electric tankless models can require multiple double-pole breakers and enough electrical capacity that the water heater alone represents a major portion of the home’s available service.
That can turn what looks like a simple water-heater conversion into a much larger electrical project.
You may need an electrical service upgrade
If your panel does not have enough capacity, installing electric tankless may require more than adding a breaker.
It can potentially mean:
- A larger electrical panel
- A service upgrade
- New heavy-gauge wiring
- Multiple dedicated 240-volt circuits
- Coordination with the utility
At that point, the cost and complexity can outweigh the benefit of going tankless.
This is especially important in older Bay Area homes where the electrical system may already be close to its limit.
Performance still depends on flow rate
Electric tankless has the same basic limitation as gas tankless:
“Endless hot water” does not mean unlimited hot water.
The heater can only raise the temperature of a certain amount of water at one time.
If several showers or fixtures are running simultaneously, the unit has to be large enough to keep up.
And the larger the unit, the more electrical power it needs.
That is where the problem starts feeding on itself.
What usually makes more sense?
If the goal is to move away from gas, we generally prefer a heat pump water heater over whole-house electric tankless.
A heat pump water heater stores hot water in a tank and heats it much more efficiently over time instead of trying to generate all of that heat instantly.
It still usually requires a 240-volt circuit, but the electrical demand is dramatically more manageable.
You also gain the efficiency advantages of heat-pump technology without needing an enormous electrical service just for the water heater.
Are there situations where electric tankless makes sense?
Yes.
Smaller electric tankless units can work well for point-of-use applications, such as:
- A remote sink
- A small ADU
- A workshop
- A bathroom with limited demand
In those situations, the electrical requirement can be much smaller and the installation may make sense.
Whole-house use is where we become much more cautious.
Why we usually don’t recommend whole-house electric tankless
If you already have a house with unusually large electrical capacity and relatively modest hot-water demand, it can work.
But for most Bay Area homeowners converting from gas, we would not spend a large amount of money upgrading the electrical system just to install whole-house electric tankless.
If the goal is electrification, a heat pump water heater is usually the better place to start.
If you’re considering electric tankless, send Water Heater Boys some information about your home, existing water heater, and electrical panel. We can help you determine whether it is realistic before you spend money on equipment.
Request an estimate or call Water Heater Boys at (650) 844-2305.