What to Know Before Installing a Tankless Water Heater in Missouri
Tankless water heaters are growing in popularity across Missouri, and for good reason. These energy-efficient systems heat water on demand, take up less space, and never run out of hot water like traditional tanks. But before you make the switch, there’s one major factor homeowners often overlook: your home’s electrical system.
Whether you're in Wildwood, Pacific, Union, Washington, or Eureka, installing a tankless water heater often requires significant electrical upgrades — especially if you’re going electric instead of gas. In this article, we’ll walk you through what you need to know before installation, including power requirements, panel capacity, and how Cain Electric ensures a safe, code-compliant setup.
How Tankless Water Heaters Work
Traditional water heaters store and maintain hot water in a tank. Tankless units, also known as on-demand water heaters, heat water only when it’s needed. This reduces standby energy loss and offers a continuous supply of hot water.
Electric tankless systems do this by rapidly heating water as it passes over high-powered electric heating elements. That heating power draws a lot of electricity — more than most standard home circuits are built to handle.
Power Requirements for Tankless Water Heaters
Most electric tankless water heaters require between 120 and 150 amps of dedicated power, depending on the model. This is in addition to your home’s existing electrical load.
If you’re switching from a tank-style electric heater, which typically uses a single 30-amp breaker, you’ll need to make major adjustments. Many tankless models require three separate 40-amp double-pole breakers and heavy-gauge wiring.
That means:
Your panel must have room for multiple new breakers
You’ll need thick wiring (often 8 AWG or larger) run directly from the panel to the unit
Your panel may need to be upgraded to 200 amps or more if it isn’t already
For homes with 100-amp or even 150-amp panels, installing an electric tankless system without upgrades is often not feasible or safe.
Signs Your Electrical Panel May Not Be Ready
Not sure if your system can handle a tankless water heater? Look for these warning signs:
Your panel is rated at 100 amps or less
You’ve experienced breaker trips when running multiple appliances
Your panel is full or lacks space for new breakers
Your lights flicker when using major devices like HVAC or laundry machines
You’re already running other high-demand appliances like EV chargers or electric ranges
Cain Electric offers full panel evaluations to determine if your home is ready for a tankless upgrade — and what changes may be required.
Learn more about our residential electrical services here.
Gas vs Electric Tankless Units
If you're still deciding between gas and electric tankless systems, here are a few considerations.
Electric tankless water heaters are often easier to install where gas isn't available, but they require much more electrical capacity.
Gas units are more common and don’t draw from your electrical panel, but they require venting and natural gas or propane lines.
Electric units are more compact and generally require less maintenance, but can be costlier to operate in areas with high electric rates.
If you choose electric, be prepared to upgrade your panel or circuits — especially in older homes.
What About Backup Power?
If you’re investing in a tankless water heater and also have or plan to install a whole-home backup generator, you’ll need to factor that in.
Electric tankless systems may not be compatible with smaller generators. Since they require a high surge of amperage when activated, they can easily overload portable or undersized standby units.
We recommend pairing electric tankless systems with larger whole-home generators rated for high-load appliances or using gas tankless models that are easier to support during outages.
Explore our whole-home generator installation services here.
Energy Savings vs Upfront Costs
Tankless water heaters can reduce energy usage over time, but the upfront cost is often higher — especially when you factor in:
Panel upgrades
New wiring and dedicated circuits
Permitting and code compliance
Unit cost and plumbing labor
It’s an investment, and like any major system change, it pays to do it right the first time. That’s where Cain Electric comes in.
Why Choose Cain Electric?
We’ve helped dozens of Missouri homeowners successfully transition to tankless systems. Our licensed electricians work alongside your plumber or contractor to ensure the electrical side of the install is:
Up to code and safe
Sized correctly for your system
Protected with proper grounding and GFCI where required
Built to handle future upgrades like solar, generators, or EV charging
We serve homeowners in Wildwood, Eureka, Washington, Union, Pacific, and surrounding areas. Whether your home is brand-new or decades old, we’ll make sure your electrical system is ready for modern demands.
Thinking About Going Tankless? Call Cain First.
Before you install a tankless water heater, make sure your home’s electrical system can handle it. Cain Electric provides honest assessments, fair pricing, and expert installation to make your upgrade safe and smooth.
Contact us today to schedule your panel evaluation or installation quote.
