A tankless electric water heater works differently than traditional tank heaters. Instead of heating and storing a tank full of water, they use high-powered heating elements to instantly heat water as it flows through the unit. This on-demand design provides the following benefits:
- Endless Hot Water: Tankless heaters supply hot water endlessly without running out. This allows you to take long showers, fill multiple tubs, run the washing machine and dishwasher simultaneously, and more without worrying about hot water capacity.
- Energy Efficiency: Because they only heat water when needed instead of maintaining a temperature tank, tankless units use up to 50% less energy than tank models. This saves significantly on electricity bills.
- Compact Size: Taking up about the size of a carry-on suitcase, tankless heaters free up valuable floor space compared to bulky tank heaters. Their wall-mounted design makes for flexible installation.
- Durability: Tankless models last up to 20 years, nearly twice as long as the lifespan of tank heaters. This reduces the need for frequent replacements.
However, to leverage these advantages fully, tankless electric heaters must be sized, installed, and maintained properly. This 4000-word guide will cover everything you need to know, from planning your installation to troubleshooting issues. Follow along step-by-step to ensure your new tankless unit works safely at optimal efficiency for years to come.
Pre-Installation Planning
Careful planning is required before installing a tankless electric water heater in your home. First, assess if a tankless model meets your household hot water requirements. If so, complete the following pre-installation steps:
Check Local Building Codes
Most localities require permits to install new water heaters. Contact your municipal building department to:
- Learn about permit and inspection requirements
- Ensure your planned installation complies with plumbing and electrical codes
This prevents potential violations that could jeopardize home insurance policies. Also, some municipalities offer rebates and tax incentives for energy efficient electric tankless heaters—so ask about any available savings.
Assess Electrical Requirements
Tankless electric units have high-wattage heating elements that require dedicated, 240-volt circuits. Consult the heater manufacturer’s documentation to determine:
- Recommended circuit breaker amperage
- Wire gauge needed to handle the electric load
- Maximum wire run length from the circuit panel
Most existing electrical panels won’t have adequate capacity to power a tankless unit. Upgrades like installing new wiring, subpanels, or service upgrades may be needed—adding $1000 or more to installation costs.
Pick an Installation Location
Ideal tankless water heater placement depends on:
- Distance from Fixtures: The closer the unit is installed to fixtures (sinks, showers, etc.) needing hot water, the less heat loss occurs in supply pipes. Mount as close as allowable by codes.
- Venting Requirements: Tankless heaters vent large volumes of moist exhaust when operating. Consider vertical and horizontal vent routing limitations specified by building codes and the manufacturer.
- Freezing Temperatures: Ensure the installation area remains above freezing. Extend supply pipes through heated spaces only and insulate against cold.
Also account for service access—unit dimensions, clearance areas, and any required condensate drains or piping.
Gather Necessary Materials
With planning complete, compile all materials needed for installation:
Tankless Electric Water Heater
- Specified electrical requirements and hot water output rate
- Safety certifications like UL listings
- Warranty of 5-10 years minimum
Mounting Bracket & Hardware
- Bracket sized for water heater dimensions
- Corrosion-resistant bolts & fasteners
Electrical Supply Components
- Dedicated double pole circuit breaker
- 240V-rated copper wire of specified gauge & insulation
- Conduit, connectors, and junction boxes
- GFCI outlet or wiring junction (for service access)
Plumbing Components
- Unions, adapters, isolation valves
- Approved vent materials (stainless steel, PVC, CPVC)
- Condensation drain tubing
- Pipe insulation with appropriate temperature rating
Installation Tools
- Wrenches, pliers, screwdrivers
- Pipe cutter, hacksaw, hole saw
- Drill and drill bits
- Multimeter
- Level
- Flashlight
This comprehensive list of materials ensures you can install your tankless water heater according to code. Next comes the hands-on installation process.
Step-by-Step Installation
With planning and materials ready, now follows the key procedure for installing the tankless water heater safely and effectively:
Step 1: Turn Off Water & Power Supplies
Start by switching off electrical and water supplies at main breakers/valves. This safeguards against electric shock or water release hazards during the tankless heater’s installation.
Step 2: Remove Old Water Heater (If Replacing)
When replacing an existing tank heater:
- Disconnect old water, electrical, and vent connections. Measure each supply line.
- Drain tank water into buckets and dispose of properly.
- Detach the tank from wall-mounting bracket and lift free of installation site.
- Cap any open pipes/wires with plugs. Clean area of any leakage or debris.
If installing a new tankless unit (not replacing an existing heater), skip to next step.
Step 3: Mount the Tankless Water Heater
Determine the ideal position per earlier planning then:
- Mark the bracket holes and drill any necessary pilot points for fasteners.
- Anchor mounting bracket to framing secure enough to hold the water heater’s full weight when filled.
- Lift unit and hang on bracket, inserting bolt heads into keyhole slots.
- Secure bottom of heater to wall with provided screw clamps if necessary.
Step 4: Connect Water Supply Piping
Run new hot and cold water supply lines of the same diameter as existing plumbing or per specifications. Key guidelines:
- Install shut-off valves near the heater inlet/outlet connections
- Use unions/adapters to transition pipe sizes if necessary
- Extend heating elements’ life by installing sediment filters on cold inlet
- Maintain smooth water flow transitions—avoid pressure-reducing valves
- Insulate all accessible hot & cold pipe sections near the unit
- Install condensation drain tubing with downward slope for moisture removal
Follow manufacturer instructions to connect inlet and outlet plumbing to labeled unit ports using provided gaskets/fittings.
Step 5: Install Electrical Supply
IMPORTANT: An electrician should complete final electrical connections per NEC codes. Key requirements:
- Dedicated double pole circuit breaker on panel with #10 AWG copper wires minimum
- Stranded AL/CU wire only inside conduit between circuit breaker and heater
- Overcurrent protection through conduit via intermediate junction boxes
- Place conduit penetration on unit’s electrical junction box knockout
Connect all ground and neutral wires. Ensure electrical cover plates and knockout plugs are reinstalled to maintain safety ratings after connections finished.
Step 6: Install Flue Venting
Tankless heaters require proper exhaust venting to remove byproducts of gas heating. Install vent materials approved by the manufacturer:
- Stainless steel vents for durability & resistance to corrosion
- Clearances from combustibles per rating sticker instructions
- Avoid 90° elbows when possible to reduce vent restriction
- Slope horizontal pipe runs back towards unit at 1⁄4 in per foot
Vent piping connects to the threaded heater exhaust connection. Secure joint with silicone sealant safe for exhaust temperatures.
Step 7: System Purge & Leak Check
With all connections complete, purge air and debris from plumbing to avoid damage:
- Close outlet valve on heater and open inlet valve.
- Open nearest hot water faucet. Let water run until flows full from faucet.
- Close faucet and open heater outlet valve. System now purged.
Check carefully for leaks at all connections and fittings using a flashlight. Tighten any seeping joints then verify leaks stopped. Monitor joints closely over first days of operation. Small leaks may go unnoticed until water damage is significant.
Post-Installation & Maintenance
Once installation finishes, a few final steps ensure your tankless water heater reliably delivers hot water for years of service life.
Power On Electrical Supply
With plumbing leaks verified fixed, restore power to new tankless unit at the circuit breaker while water remains running. Check for proper operation using the manufacturer troubleshooting guide if needed.
Flush the Heat Exchanger
Mineral sediment accumulates inside the units narrow heat exchanger channels during construction. Flush the exchanger per manufacturer instructions using system purge valves. Repeat flushing annually along with:
- Checking vent piping and drain lines for blockages
- Hot/cold pipe insulation integrity
- Servicing filters and heating elements
- Verifying electric connections are corrosion-free
Adjust Water Temperature
The final step sets hot water output temperature on the unit or adjustable thermostatic tap:
- Use an accurate digital thermometer to measure temperature
- Start around 120°F then have users test shower/tap for preferred temp
- Maximum is 125°F to avoid scalding per plumbing codes
Also Read: Under-Sink Water Heater Installation in 5 Easy Steps
Wrapping Up
We’ve covered the entire process of installing an electric tankless water heater successfully. While the installation is advanced, properly sizing and placing your unit as outlined simplifies each step. Refer to the manufacturer literature if unsure about any specifics. Additionally, consult licensed tradespeople in your area to assist if necessary.
Done correctly, your new high-efficiency electric tankless heater will supply endless hot water for all household needs while saving on operational costs for years to come. Maintain it properly and your family can enjoy reliable hot water for the next 20 years.