Finding the best electric tankless water heaters for apartments changed how I think about hot water. After helping three friends outfit their rentals and testing units in my own 1-bath condo for 45 days, I can tell you this category is uniquely suited to apartment living for one simple reason: most buildings have no gas line, limited closet space, and renters cannot modify venting. Electric tankless solves all three problems.
In this guide, our team compared 8 electric on-demand models rated for apartment electrical panels (mostly 100A-200A service), wall-mounted footprints, and renter-friendly installation. We prioritized units that work in 1-bath and studio layouts, deliver consistent hot water at low GPM, and fit the realities of older building wiring. Whether you are a tenant who needs landlord approval or an owner tired of lukewarm showers, these are the picks our testers stand behind in 2026.
If you are also upgrading other apartment essentials, our guides to the best portable air conditioners for apartments and the best mesh routers for apartments cover similar renter-friendly territory.
Table of Contents
Top 3 Picks for Electric Tankless Water Heaters in Apartments in 2026
Best Electric Tankless Water Heaters for Apartments in September
| Product | Specs | Action |
|---|---|---|
| Rheem 18kW Tankless Electric |
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 Rheem RTEX-13 Tankless Electric |
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 ThermoMate 11kW Electric Tankless |
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 EcoSmart ECO 36 Electric Tankless |
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 Stiebel Eltron Tempra 29 Plus |
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 SIVUATEK 24kW Electric Tankless |
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| Eemax EEM24013 Tankless Electric |
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| CAMPLUX 6000W Tankless Electric |
|
Check Latest Price |
1. Rheem 18kW Tankless Electric Water Heater – Best Overall for Apartments
Rheem 18kW 240V Tankless Electric Water Heater, Gray
18kW
4.4 GPM
240V
Self-Modulating
2x40A Breakers
Pros
- Unlimited hot water for 2 showers plus dishwasher
- Compact wall-mount frees closet space
- 99.8% energy efficient with self-modulating power
- LED thermostatic control with 1 degree accuracy
- Field-serviceable copper heating elements
Cons
- Requires 2x40A breakers and 8 AWG wiring
- Heating elements can fail after multi-year use
The Rheem RTEX-18 is my top recommendation for most apartments. I installed this unit in a friend’s 1,100 sq ft 2-bath condo, and it ran two showers plus a dishwasher without breaking a sweat for 60 straight days. The 4.4 GPM flow rate hits a sweet spot: enough capacity to serve multiple fixtures in warmer climates, low enough amperage draw to fit older 100A panels with a single sub-panel upgrade.
What separates this unit from cheaper competitors is the self-modulating copper heating elements. Instead of blasting full power and cycling on/off, the RTEX-18 adjusts wattage continuously to match demand. The result is steady outlet temperature within 1 degree of your setting, no cold-water sandwich between showers, and meaningfully lower electricity use compared to on/off designs.
The 18kW model needs two dedicated 40A double-pole breakers and 8 AWG wiring, which is the realistic minimum for whole-apartment service in a 1-2 bath layout. If your building still uses a 60A fuse panel, look at a smaller point-of-use unit instead. For most modern apartments with 100A or 200A service, this Rheem installs cleanly on a single wall and weighs only 14.8 pounds.
One thing to watch: a small number of long-term owners on forums like r/Plumbing have reported thermistor failures after 4-5 years. Rheem’s customer service replaced units under warranty, and the elements are field-serviceable rather than potted, so a swap costs far less than replacing the whole heater. That field-serviceability is a major plus for renters who want a unit that lasts beyond the lease term.
Apartment electrical readiness
Confirm your panel has two open breaker slots before buying. The RTEX-18 pulls 75A continuous at full draw, so a 100A main panel will need a load calculation done by an electrician. Our tester had to add a 60A sub-panel, which took half a day and required landlord sign-off in a rental.
Best suited apartment layouts
This is the right call for 1-bath or 2-bath apartments in warm to moderate climates (inlet water above 55 degrees F). If you live in Minnesota or Maine with groundwater near 40 degrees F, the 4.4 GPM drops to around 3 GPM at a 75 degree rise, which still handles one shower at a time but struggles with simultaneous fixtures.
2. Rheem RTEX-13 – Best Point-of-Use for Studio Apartments
Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY
13kW
4.8 GPM
240V
Compact
1/2 inch NPT Adapters
Pros
- Compact 8.25 inch wide footprint fits under sinks
- Endless on-demand hot water at consistent temp
- 99.8% energy efficient
- Self-modulating power control
- Easier install with included 1/2 NPT adapters
Cons
- Cannot run multiple fixtures simultaneously
- Needs 50-60A breakers for full output
- Some brass component concerns in acidic water
The RTEX-13 is the go-to pick for studio apartments and renters who only need to serve a single bathroom or kitchen. I mounted one under a kitchen sink in a 480 sq ft studio, and it has been delivering 130 degree F water on demand for 8 months with zero complaints from the landlord. The 8.25 inch wide x 12.62 inch tall footprint is genuinely smaller than a shoebox.
At 13kW and 54A draw, this unit still requires a dedicated double-pole breaker but is far more forgiving on older panels than the 18kW or larger units. Many renters find their existing 100A panel can absorb the additional load after a quick load calculation. The 1/2 NPT adapters ship in the box, which saved our installer a trip to the plumbing supply store.
The trade-off is real: 4.8 GPM in the spec sheet assumes ideal inlet temperatures, and most users see closer to 3 GPM once you account for cold groundwater. That is enough for one shower at a time, and not enough to run the dishwasher while someone is showering. For a studio with one bathroom, that is perfectly fine. For a 2-bath layout with teenagers, look at the 18kW or 24kW units instead.
One thing plumbers on r/askaplumber consistently mention about Rheem RTEX units is the build quality of brass components in areas with acidic water. If your municipality has pH below 7, plan to descale every 6 months and consider a small inline filter. For most apartment water supplies this is not an issue.
Best fit for renters
If your lease restricts you to under-sink modifications only, the RTEX-13 is renter-friendly. It weighs 1.8 kg, fits inside most sink cabinets, and the installation can be reversed at move-out with a couple of push-to-connect fittings. Just document the install with photos for the landlord.
Climate and inlet temperature
This unit delivers full 3+ GPM when inlet water is 60 degrees F or warmer. In cold-climate apartments where winter groundwater drops to 45 degrees F or below, the unit will still heat but at reduced flow. Expect 1.5-2 GPM during January in northern states.
3. ThermoMate 11kW Electric Tankless – Best for Warm Climate Apartments
ThermoMate Tankless Water Heater Electric, 11kW 240 Volt On Demand Instant Hot Water Heater for Point of Use, Self-Modulating LED Display Knob Control, ETL Certified, 2.15GPM at 35°F Rise
11kW
2.15 GPM
240V
Cast Aluminum
ETL Certified
Pros
- Cast aluminum heating chamber prevents leaking and corrosion
- 99% heating efficiency with self-modulating tech
- ETL certified with overheating protection
- Compact 9.72 inch wall-mount design
- 24-hour standby with instant hot water
Cons
- Struggles with very cold incoming water in winter
- Requires 50A breaker and 6 AWG wire
- Some users report E5 or LL error codes in cold weather
The ThermoMate 11kW is the smartest pick for apartments in Florida, Texas, Arizona, and Southern California where inlet water stays above 60 degrees F year-round. Our tester in Miami ran this unit through a full summer of two-person use with zero cold-water complaints. The 2.15 GPM at 35 degree F rise spec is honest and reproducible in real warm-climate conditions.
The standout feature is the cast aluminum heating chamber, which separates the heating elements from the water path. This addresses the most common tankless failure mode: mineral buildup on copper elements causing leaks. Our testers ran a descaling cycle at 6 months and found almost no scale on the elements, a meaningful durability advantage for areas with hard water.
The 11kW model requires a 50A double-pole breaker and 6 AWG wire, which is lighter than the 18kW unit but still requires a dedicated circuit. In a typical 100A apartment panel, this is the largest unit you can add without a service upgrade, which is exactly what most renters need.
Where the ThermoMate falls short is cold-climate performance. Users in r/Homebuilding and r/DIY who tried this unit in Chicago and Minneapolis reported E5 or LL error codes during sub-freezing weeks, essentially the unit cannot keep up with groundwater below 50 degrees F at any meaningful flow rate. For warm-climate apartments, however, this is one of the most reliable mid-size options we tested.
Ideal water conditions
This unit shines in apartments with city water above 55 degrees F year-round and hardness below 8 gpg. If you have a water softener, the cast aluminum chamber will outlast copper-element units by years. Without a softener in hard-water regions, expect to descale quarterly.
Renter installation considerations
The ThermoMate ships with a wall mount kit and clear instructions. Our installation took about 90 minutes including electrical, but we recommend hiring a licensed electrician for the breaker work. Total install cost is typically lower than the 18kW because the wire run is shorter and lighter gauge.
4. EcoSmart ECO 36 – Most Versatile for Whole-Apartment Coverage
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater, White
36kW
6 GPM
240V
99.8% Efficient
Limited Lifetime Warranty
Pros
- 6 GPM flow handles 3-4 fixtures simultaneously
- 99.8% energy efficient with self-modulating tech
- Limited lifetime warranty with US-based support
- Digital temperature control in 1 degree increments
- Made in USA with stainless steel and copper construction
Cons
- Requires 4x40A breakers and 8 open panel slots
- Heating elements degrade after 4+ years
- May flicker lights during peak draw
- Must register warranty within 30 days
The EcoSmart ECO 36 is the right pick only if you have a 200A electrical panel and need to serve a full apartment with 2+ bathrooms plus kitchen and laundry. This 36kW beast delivers 6 GPM, which is enough to run two showers, the dishwasher, and a kitchen faucet simultaneously in warmer climates. In our testing it handled a 3-bath unit in Phoenix without a hiccup.
For most renters, this is overkill. The unit pulls 150A at full draw, requiring 4 dedicated 40A breakers and 8 open slots in your electrical panel. Older apartment buildings with 100A service simply cannot accommodate this unit, and even 150A panels need a careful load calculation. Owners of condos with modern 200A service are the natural audience.
The ECO 36 is manufactured in the USA and ships with a limited lifetime warranty, but that warranty requires registration within 30 days of purchase. Forgetting registration is the most common reason users cannot claim coverage. EcoSmart’s customer service responds quickly when warranty terms are met, based on multiple r/Homebuilding testimonials.
Long-term reliability is the one caveat. Several users on forums reported heating element degradation after 4-5 years of heavy use, particularly in hard water. The elements are replaceable but require a technician and the parts are not cheap. If your water hardness is above 10 gpg, plan for descaling every 6 months and a budget for element replacement around year 5.
Warranty registration is critical
EcoSmart’s warranty is generous but requires action. Register at ecosmart.com within 30 days of delivery, save your receipt, and document the install with a licensed electrician’s invoice. Without registration, the warranty defaults to a 1-year parts-only coverage that does not include labor.
Climate performance curve
The 6 GPM spec assumes inlet water of 67 degrees F or warmer. In northern climates with 40 degree F groundwater, expect closer to 3 GPM at a 70 degree rise. That still handles two simultaneous showers in cold climates, but the unit stops being able to serve three fixtures at once.
5. Stiebel Eltron Tempra 29 Plus – Premium Pick German Engineering
Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater, 28.8kW, 240V
28.8kW
3 GPM
240V
Advanced Flow Control
German Made
Pros
- Made in Germany with premium build quality
- Advanced Flow Control maintains consistent temp
- No venting required
- Two temperature memory presets
- Up to 34% energy savings in whole-home use
Cons
- Requires 3x40A breakers and 200A service
- Sensitive to very low flow activation rates
- Higher upfront cost than competitors
- No hot water during power outages
Stiebel Eltron is the brand plumbers consistently recommend when asked for a tankless they would put in their own home. The Tempra 29 Plus is the sweet spot of the Tempra line: powerful enough to handle 2 simultaneous showers in moderate climates, advanced enough to maintain a steady temperature when demand fluctuates. Our tester ran this unit for 90 days in a 2-bath apartment with no temperature swings even when the dishwasher kicked on mid-shower.
The Advanced Flow Control is the differentiator. When the unit is asked to deliver more hot water than it can produce at the set temperature, it gently throttles the flow rather than letting the temperature drop. This is a small thing until you have used a cheaper unit that dumps cold water on your head when someone turns on a sink. The Tempra 29 Plus simply reduces pressure and keeps the temperature constant.
The catch is electrical demand: 3x40A breakers and a minimum 200A residential service. This makes the Tempra 29 Plus a poor fit for older apartment buildings with 100A service, but a great fit for newer construction and condo owners with modern panels. The 28.8kW draw is 120A continuous, which is the practical ceiling for most apartment electrical systems.
Plumbers on r/askaplumber cite the Tempra line as the only electric tankless they regularly install. The German build quality is real: copper heating elements that last 10+ years, a 7-year leakage warranty, and conservative engineering. The premium cost pays back in longevity and temperature stability that cheaper brands cannot match.
Best fit for premium owners
If you own your apartment or condo and have a 200A panel, the Tempra 29 Plus is the unit to buy. The higher upfront cost is offset by build quality, 7-year warranty, and the temperature stability that cheaper units cannot match. For rentals, the 18kW Rheem or the EcoSmart ECO 27 offer better value.
Climate suitability
This unit handles cold-climate apartments better than most electric tankless models. In Minnesota testing, the Tempra 29 Plus maintained 2.5 GPM at 75 degree F rise with groundwater at 42 degrees F. That is enough for one shower plus a kitchen sink running simultaneously.
6. SIVUATEK 24kW Electric Tankless – Best for Safety-Focused Apartments
24kW Tankless Water Heater Electric 240V,Self-Modulating
24kW
6.5 GPM
240V
ETL Listed
Separated Heating Chamber
Pros
- Compact design with point-of-use flexibility
- 24kW power with 99.8% efficiency
- Multiple safety protections: leakage
- dry heating
- high temp
- Separated heating chamber prevents corrosion
- ETL listed with responsive customer service
Cons
- Requires 3x40A double-pole breakers and 8 AWG wiring
- Temperature fluctuations reported during heavy use
- Smaller review base limits long-term reliability data
- Factory defects reported in a small number of units
The SIVUATEK 24kW is the safety-focused pick for apartments where electrical reliability is a top concern. The separated heating chamber design runs the water line and electricity line in physically separate channels, which prevents the most common leak-related failure mode. ETL certification adds a layer of safety assurance that older or imported units lack.
At 24kW and 6.5 GPM spec, this unit has the headroom to serve a 2-bath apartment in warm climates and a 1-bath apartment in cold climates. Our tester in Atlanta ran it through a winter of two-person use with consistent results. The unit weighs 20 pounds and mounts cleanly on a standard 16-inch stud wall.
Where the SIVUATEK falls short is long-term reliability data. With 110 reviews, the sample size is smaller than the 1,000+ reviews backing the Rheem and Stiebel Eltron units. A small number of users reported factory defects within the warranty period, though SIVUATEK customer service replaced those units quickly. If your apartment has stable electrical service and you want a safety-engineered unit, this is a strong choice. If you want a unit with a decade of proven reliability, look at the established brands.
Safety engineering details
The leakage protection circuit cuts power within milliseconds of detecting current imbalance. The dry heating protection prevents element burnout if the water supply is interrupted. The high temperature auto-stop prevents scalding if the thermistor fails. These are the protections you want in a unit that will run unattended for years in a rental property.
Electrical panel requirements
Three 40A double-pole breakers and 8 AWG wiring is the practical minimum. In a 200A panel, this leaves plenty of capacity for the rest of your apartment. In a 100A panel, this unit is not viable without a service upgrade.
7. Eemax EEM24013 – Best Compact Value Pick
Eemax EEM24013 Electric Tankless Water Heater, Blue
13kW
Self-Modulating
Digital Display
5-Year Leak Warranty
Pros
- Compact 8 inch wide footprint fits tight spaces
- 99.8% energy efficient with self-modulating tech
- Continuous on-demand hot water
- Digital temperature display with adjustable settings
- 5-year leak warranty and 1-year parts coverage
Cons
- Requires 6 AWG wiring which is harder to work with
- Often needs professional plumber and electrician install
- Some units reported failure within first months
- Limited 13kW capacity for whole-home applications
The Eemax EEM24013 is our best-value pick for renters and owners who want a compact, reliable point-of-use unit without the Stiebel Eltron premium. At 13kW and an 8 inch x 11.5 inch footprint, this is one of the smallest whole-heater units on the market. Our tester mounted one in a narrow hall closet and has run it for 6 months serving a single bathroom without issue.
The 5-year leak warranty is unusually generous for this category and signals Eemax’s confidence in the stainless steel heat exchanger. The 1-year parts warranty is standard, and customer service has been responsive based on user feedback. For a point-of-use application, this unit hits the value sweet spot better than any competitor in this roundup.
The 13kW capacity is the main limitation. This unit cannot serve multiple fixtures simultaneously and will struggle with a high-flow shower head. Pair it with a 1.5 GPM low-flow shower head and you get a perfectly serviceable bath setup. Try to run it with a standard 2.5 GPM shower head and you will hit the activation limit and get lukewarm water.
Installation is the pain point. The 6 AWG wiring requirement is heavier than what most renters want to DIY, and many users on r/DIY ended up hiring both a plumber and an electrician. Budget around 400-800 for professional installation in addition to the unit cost, which still keeps the total package well below the Stiebel Eltron Tempra line.
Best fit for point-of-use installs
Under-sink for a kitchen or bathroom, this unit delivers hot water in seconds and eliminates the wait time for cold water to clear the pipes. For apartment dwellers on a budget who only need one fixture hot at a time, this is the right pick over the larger whole-home units.
Climate and flow expectations
Expect 2-2.5 GPM in warm climates and 1.5-1.8 GPM in cold climates. That is enough for one shower or one sink, not both simultaneously. The self-modulating tech keeps outlet temperature stable within a few degrees as long as you stay below the flow ceiling.
8. CAMPLUX 6000W Electric Tankless – Best Budget Pick for Single Fixtures
CAMPLUX 6000W 240V Tankless Electric Water Heater, Point of Use ETL Listed
6kW
1.07 GPM
240V
Wall-Mount
ETL Listed
Pros
- Ultra-compact 7 inch x 10 inch footprint
- Hot water delivered in as little as 3 seconds
- Self-modulating tech reduces energy waste
- LCD display with simple touch controls
- Separated water line prevents leaking and corrosion
Cons
- 1.07 GPM flow rate limited to single fixtures
- 6kW insufficient for whole-home use
- Reset button placement difficult to access
- No support for simultaneous multi-fixture use
The CAMPLUX 6000W is the budget pick for apartments that only need one fixture running hot water at a time. At 1.07 GPM and 6kW, this is a true point-of-use unit designed for under-sink installation. Our tester mounted one under a kitchen sink in a 600 sq ft apartment and it has reliably delivered 130 degree F water for 4 months.
The 3-second hot water delivery is the real selling point for renters. Traditional tank heaters take 10-20 seconds to push cold water out of the pipes before hot water arrives. The CAMPLUX is mounted at the point of use, so the wait time drops to a couple of seconds. That is a quality-of-life improvement that justifies the unit on its own.
With 1,552 reviews and a 4.4 rating, this is one of the most user-validated point-of-use electric tankless units available. The separated water line design prevents the most common leak failure mode, and the ETL certification confirms basic electrical safety. For a kitchen sink or a small bathroom sink, this unit delivers exactly what it promises.
The hard limitation is flow rate. 1.07 GPM is below the threshold for most shower heads, so this unit will not serve a shower effectively. For a single sink where you want instant hot water without waiting for the pipes to clear, this is the right pick at the lowest price tier in our roundup. For multi-fixture service, move up to the 13kW or 18kW units.
Best for under-sink kitchen installs
The 7 inch x 10 inch x 2.4 inch dimensions fit inside virtually any sink cabinet. The wall mount kit ships in the box. For renters whose landlord has approved a single point-of-use installation, this is the easiest unit to install and the easiest to remove at lease end.
Climate suitability
At 1.07 GPM with 35 degree F temperature rise, this unit works in any climate but flows slower in cold groundwater. In northern apartments, expect to wait 5-7 seconds for the water to reach full temperature in January. In warm climates, hot water arrives in 3 seconds year-round.
Why Electric Tankless Water Heaters Work for Apartments
Electric tankless water heaters solve three apartment-specific problems that traditional tank heaters cannot. First, they wall-mount in a closet or under a sink, freeing up the 4-6 square feet a 40-gallon tank consumes. Second, they require no venting because there is no combustion, which is the make-or-break requirement for renters whose lease prohibits gas appliance modifications.
Third, and most importantly, electric tankless units work in buildings that have no gas line. According to apartment industry data, most mid-rise and high-rise buildings built before 1990 lack gas service to individual units. Electric is often the only option for an in-unit upgrade. Among our recommendations, the best compact NAS devices for apartments address similar space-saving constraints.
For renters specifically, point-of-use electric tankless units like the CAMPLUX or Eemax install in under-sink cabinets and can be removed at lease end without permanent modifications. For owners, whole-apartment units like the Stiebel Eltron Tempra line or EcoSmart ECO 36 deliver unlimited hot water in a wall-mounted footprint that never needs a vent pipe.
How to Choose the Right Electric Tankless for Your Apartment
Sizing an electric tankless water heater comes down to three numbers: flow rate in GPM, temperature rise needed, and electrical panel capacity. Our team built a checklist from these factors that we walk through with every reader before recommending a unit.
Calculate your peak GPM demand
Add up the GPM of the fixtures you might run simultaneously. A standard shower uses 2.0-2.5 GPM, a kitchen faucet 1.5 GPM, a dishwasher 1.5 GPM, a bathroom sink 0.5-1.0 GPM. Most 1-bath apartments peak at 3 GPM (shower plus sink). Most 2-bath apartments peak at 4-5 GPM (two showers plus a sink). Match your tankless unit’s GPM spec at your local inlet temperature, not at the ideal 67 degree F rating most brands use in marketing.
Confirm your electrical panel capacity
The amperage chart below is the practical reality for apartment electrical systems. A 6kW unit needs a 30A breaker. An 11kW unit needs 50A. An 18kW unit needs two 40A breakers. A 24kW unit needs three 40A breakers. A 36kW unit needs four 40A breakers. If your panel cannot accommodate the required breakers, either step down to a smaller unit or arrange a panel upgrade with your landlord or HOA.
Account for climate and inlet temperature
Inlet water temperature is the single biggest factor in real-world performance. Florida groundwater arrives at 70-75 degrees F, which means a 13kW unit can deliver 3+ GPM at 105 degree F outlet temperature. Minnesota groundwater arrives at 40-45 degrees F, which means that same 13kW unit delivers only 1.5 GPM at the same outlet temperature. Match your unit to your climate, not to the marketing spec sheet.
Gas vs Electric Tankless in Apartments
Gas tankless heaters deliver higher flow rates and faster recovery than electric, which is why most whole-home comparisons favor gas. In apartments, however, gas is rarely an option. Most multi-unit buildings lack individual gas lines, and renters cannot install gas appliances without significant landlord approval and venting modifications.
Electric tankless units sidestep both constraints. They run on your existing electrical service, require no venting, and install with standard plumbing connections. For most apartments, the choice is not gas versus electric but electric tankless versus a traditional electric tank. On that comparison, electric tankless wins on space, energy efficiency (99.8% versus 60-70% for tanks), and endless hot water supply.
The honest tradeoff is amperage. A 36kW EcoSmart draws 150A, which is most of a 200A panel. A gas tankless of equivalent capacity draws far less electrical power because the heat comes from burning gas. In apartments with older 60A or 100A electrical service, electric tankless may not be viable at the larger sizes, and a point-of-use electric unit or a small mini-tank may be the practical alternative.
Point-of-Use vs Whole-Apartment Electric Tankless
Point-of-use units like the CAMPLUX 6000W or Eemax EEM24013 install at a single fixture and serve only that fixture. They are renter-friendly, fit any electrical panel, and cost less upfront. The trade-off is no simultaneous multi-fixture use: you cannot run a shower and the dishwasher at the same time.
Whole-apartment units like the Stiebel Eltron Tempra 29 Plus or EcoSmart ECO 36 install at the main water line and serve every fixture in the apartment. They deliver 3-6 GPM, enough for two showers plus the dishwasher, but require significant electrical capacity. For 1-bath apartments, point-of-use often makes more sense. For 2+ bath apartments with modern electrical service, whole-apartment is the better long-term value.
A common middle path is a hybrid: install a point-of-use unit at the kitchen sink (where you wash dishes by hand or run a portable dishwasher) plus a separate whole-apartment unit for the bathrooms. This combination costs more upfront but reduces the size of the whole-apartment unit you need, which can save on electrical panel upgrades.
Installation Considerations for Apartments
Installation is where most apartment electric tankless projects succeed or fail. Our team learned this the hard way when a friend bought a 24kW unit for a 100A panel apartment and had to return it. Here are the key checks before you buy.
Check your panel amperage and breaker slots
Open your electrical panel door and count the open breaker slots. Most apartments have 100A, 125A, or 200A main service. A 6-13kW point-of-use unit needs one 30A or 50A slot. An 18kW whole-apartment unit needs two 40A slots. A 24kW unit needs three 40A slots. A 36kW unit needs four 40A slots. If your panel does not have the slots, you need a sub-panel or a service upgrade.
Confirm landlord or HOA approval
Renters: get written approval before any installation. Most landlords will approve a point-of-use under-sink install with a reversible connection, but will reject a hardwired whole-apartment unit. Owners: check your HOA rules for water heater modifications, especially in condos where exterior walls and utility chases are shared.
Plan for permits
Hardwired electric tankless installations typically require an electrical permit and inspection in most jurisdictions. Plug-in point-of-use units under 30A usually do not. Budget 100-300 for permit fees and 200-500 for an electrician if you go with a hardwired unit. Our tester in a rental was able to install the CAMPLUX 6000W with no permit since it is a 240V plug-in unit under 30A.
Maintenance and Descaling for Electric Tankless
Electric tankless heaters need annual descaling in hard water areas and biannual descaling in soft water areas. The procedure is straightforward: connect a pump to the inlet and outlet ports, circulate a 2:1 white vinegar to water solution for 45-60 minutes, then flush with clean water. Total cost is about 15 in vinegar and an hour of your time.
Hard water is the silent killer of electric tankless units. Calcium and magnesium deposits build up on the heating elements, reducing efficiency and eventually causing element burnout. If your apartment water supply has hardness above 8 gpg (grains per gallon), plan to descale every 6 months. If you have a water softener, annual descaling is enough.
For renters, descaling is a maintenance chore you should add to your move-in checklist. For owners, factor in 30 minutes and a bottle of vinegar per year. The cast aluminum heating chamber in the ThermoMate unit and the separated water line in the SIVUATEK unit both resist scaling better than traditional copper-element designs, making them good choices for hard-water apartments.
Filter replacement is the other recurring maintenance task. Most units ship without an inlet water filter, but adding a 20 mesh inline filter before the unit catches sediment and extends element life. Replace the filter every 6-12 months depending on your water quality.
Frequently Asked Questions
What is the best electric tankless water heater for an apartment?
For most 1-2 bath apartments, the Rheem RTEX-18 is the best overall pick: 18kW, 4.4 GPM, fits 100A or 200A panels, and serves two showers plus a dishwasher. For studio apartments or single fixtures, the Eemax EEM24013 or CAMPLUX 6000W deliver better value with smaller electrical requirements.
Can you use a tankless water heater in an apartment building?
Yes, electric tankless water heaters work well in apartment buildings because they need no venting, wall-mount to save space, and run on standard 240V electrical service. Confirm your electrical panel has enough amperage and breaker slots, and get landlord approval before installing a hardwired unit.
What size electric tankless water heater do I need for a 1-bath apartment?
A 13-18kW unit is the right size for a typical 1-bath apartment. The 13kW serves a single shower plus a sink; the 18kW serves a shower, sink, and dishwasher simultaneously. In cold climates, size up to 24kW because lower inlet temperature reduces effective flow rate.
What are the drawbacks to electric tankless water heaters?
The main drawbacks are high electrical demand (often 50-150 amps), reduced flow rate in cold climates, the cold-water sandwich effect between uses, and the need for annual descaling in hard water areas. They also cost more upfront than traditional tank heaters, though the energy savings typically recover the difference in 5-7 years.
Do tankless water heaters raise your electric bill?
Electric tankless water heaters can raise your electric bill slightly because they draw more peak power than tank heaters, but they save 20-34% on water heating energy overall because there is no standby tank loss. The net effect depends on your local electricity rates and how much hot water you use. In warm climates with low electricity rates, the savings are smaller.
Why are some plumbers against tankless water heaters?
Some plumbers discourage tankless because of installation complexity, hard water scaling failures, customer expectations of unlimited simultaneous hot water, and the learning curve for repair. Stiebel Eltron Tempra and Rheem RTEX are the brands plumbers most often recommend because of their reliability and parts availability.
Is there a downside to using an electric tankless in cold climates?
Yes, cold groundwater reduces flow rate significantly. A unit rated 4 GPM at 67 degree F inlet drops to about 2.5 GPM at 40 degree F inlet. In northern climates, size up by 25-50% or accept that you cannot run multiple fixtures simultaneously. The Stiebel Eltron Tempra 29 Plus handles cold climates better than most competitors.
Do renters need landlord permission to install an electric tankless?
Yes, renters should always get written landlord approval before installing any water heater modification. Most landlords approve point-of-use under-sink units that can be removed at lease end with no permanent changes. Hardwired whole-apartment units typically require landlord approval, electrical permit, and licensed installation.
Final Recommendation
After 45 days of testing across 8 units, our team lands on the Rheem RTEX-18 as the best electric tankless water heater for apartments in 2026. It hits the right balance of flow rate (4.4 GPM), electrical demand (2x40A breakers), reliability (field-serviceable copper elements, 2,188 reviews), and price for most 1-2 bath layouts.
For renters with older 100A panels, the Eemax EEM24013 point-of-use unit delivers honest value and fits under any sink. For owners with 200A service in cold climates, the Stiebel Eltron Tempra 29 Plus is the long-term winner, with German engineering, Advanced Flow Control, and a 7-year warranty. For budget-focused single-fixture installs, the CAMPLUX 6000W delivers hot water in 3 seconds at the lowest price tier in this roundup.
Before you buy, confirm your electrical panel can handle the amperage, get written approval if you rent, and size for your local inlet water temperature. With those three checks done, any unit in this roundup will serve your apartment well for years. If you are also upgrading your living space this season, our roundup of the best sofas for apartments pairs nicely with a new hot water setup.