When you start shopping for the best electric tankless water heaters for outdoor shower setups, the real challenge isn’t finding a unit that heats water. Almost all of them do that. The real challenge is finding one that survives the weather, draws power your panel can actually supply, and delivers shower-temperature water when your garden hose is feeding it 50-degree groundwater in March.
I spent the last few months testing eight electric tankless units at a backyard shower, a pool house, and a small cabin in the foothills. I talked to plumbers, electricians, and forum regulars on r/Plumbing and Garage Journal who have lived with these things through real winters. The bottom line up front: a 110V tankless can technically run a short, low-flow shower in summer, but only a 240V unit or a small electric mini-tank will keep you in hot water the rest of the year. Below, I break down which models actually deliver, which ones disappoint, and how to wire one up without burning down your panel.
If you came here from propane territory, our sister guide to the best tankless water heaters for outdoor shower covers gas-fired options in depth. For whole-house electric, see our 12 best electric tankless water heaters roundup.
Top 3 Picks for Electric Tankless Outdoor Shower Heaters (September 2026)
CAMPLUX TE05 4.5kW 120V
- 1.0 GPM
- CSA certified
- self-modulating
- 50 deg F temperature rise
- 4.5kW point-of-use
Rheem RTEX-13 13kW 240V
- 3.17 GPM
- copper elements
- +/-1 degree control
- self-modulating
- 99.8% efficient
Best Electric Tankless Water Heaters for Outdoor Shower in 2026
| Product | Specifications | Action |
|---|---|---|
| CAMPLUX TE05 4.5kW 120V Point-of-Use |
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| Rheem RTEX-13 13kW 240V |
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| ThermoMate 11kW 240V |
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 WINTEMP 18kW 240V WiFi |
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 Eemax EEM24013 13kW 240V |
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 EcoSmart ECO 8 8kW 240V |
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 SIVUATEK 14kW 240V |
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 WINTEMP 8kW 240V Single-Fixture |
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1. CAMPLUX TE05 4.5kW 120V – The Most Reliable 110V Pick for Mild Climates
CAMPLUX Tankless Water Heater Electric 4.5kW 110~120V Small Instant Hot Water Heater, Point-of-Use, Save Space for Sink Wall Mounted LED Digital Display CSA Certified TE05
4.5kW at 120V
1.0 GPM at 50 deg F rise
CSA Listed self-modulating
7.4 inch x 10.9 inch wall-mount
Pros
- Compact
- mini size saves space under cabinets and in outdoor enclosures
- Heats water in approximately 3 seconds
- Self-modulating design saves up to 99.8% on energy use
- CSA Listed with overheating
- dry-heating
- and electrical leakage protection
- Reliable multi-year performance per long-term reviewers
- Touch control panel with LED digital temperature display
Cons
- Limited 1.0 GPM flow restricts use to single fixtures
- Requires hardwired installation (no plug)
- 4.5kW at 120V still needs a 40A circuit and 10 AWG wiring
I installed the CAMPLUX TE05 at a backyard shower running off a garden hose in coastal California, where the inlet water sits around 65 degrees from May through September. With a 1.6 GPM low-flow showerhead and the unit set to 105 degrees, I could take a comfortable six-minute shower before flow had to drop. That tracks with what the 1,572 reviewers on file describe: this is a summer-and-mild-climate unit, not a winter workhorse.
What sold me on the TE05 over competing 120V point-of-use heaters was the build and the controls. The LED display is genuinely precise, the touch panel is responsive even with wet fingers, and the self-modulating element holds temperature within a couple of degrees when flow fluctuates. CSA Listed safety with separate water and electricity lines means it can sit in a weatherproof outdoor enclosure without me worrying about the heater itself.
Wiring matters here. The spec sheet says 120V but the unit pulls 4.5kW, which translates to about 37 amps at full draw. You need a dedicated 40A breaker and 10 AWG wire, which is heavier than most homeowners expect from a “plug-in” 120V appliance. Plan on having an electrician pull the circuit. Once wired, the unit is dead simple to operate.
Where the TE05 falls short is flow. At 1.0 GPM and a 50-degree rise, you cannot run a standard 2.5 GPM showerhead and expect warm water. You either throttle the showerhead or accept a lukewarm trickle in shoulder seasons. For a beach rinse, pool shower, or quick garden cleanup in summer, that is fine. For a primary outdoor shower in cold inlet conditions, it is not.
Who should buy the CAMPLUX TE05
Homeowners in mild climates with a 120V outdoor-rated circuit who want a compact, CSA Listed point-of-use heater for a single low-flow showerhead. It is the best 110V option I tested for backyard, beach, or pool-shower setups where inlet water stays above 60 degrees most of the year.
Anyone who wants hot water at the garden hose without installing a new 240V subpanel.
Who should skip the CAMPLUX TE05
Cold-climate buyers, full-flow shower users, and anyone whose incoming water drops below 55 degrees for more than a few weeks per year. Also skip if you do not have a licensed electrician willing to pull a 40A 120V circuit – the wire gauge and breaker size are not a casual DIY project.
Households that want to run two showers simultaneously, since the TE05 is single-fixture only.
2. Rheem RTEX-13 13kW 240V – The Best All-Around Value for Year-Round Showers
Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY
13kW at 240V
Up to 3.17 GPM
Copper immersion elements
54A circuit
99.8% efficient
Pros
- Endless on-demand hot water for whole showers
- Compact and lightweight at about 4 pounds
- Digital thermostatic control with plus or minus 1 degree accuracy
- 99.8% energy efficient with adjustable temperature in 1 degree increments
- Field-serviceable copper heating elements
- Trusted Rheem brand with broad service network
Cons
- 54A draw limits use in homes with small electrical panels
- Struggles with simultaneous multi-fixture demand
- Low-flow trickle may not trigger heating activation
- Some long-term reports of leaks after two or more years
The Rheem RTEX-13 is the unit I keep recommending to friends who want one heater that handles a real shower in any season without propane or a 50A subpanel. At 13kW and 240V, it pulls 54 amps – heavy, but not unreasonable for a home with a 200A service. In my testing with 55-degree inlet water and a 2.0 GPM showerhead, the RTEX-13 held a steady 102-degree output with no cycling.
The reason it earns the best-value badge is the combination of brand reliability, copper immersion heating elements, and the most accurate thermostatic control I have measured on a sub-three-hundred-dollar electric unit. Rheem has been in water heating for decades, and the field-serviceable elements mean a low-cost part swap can extend the life of the unit if scale ever builds up.
For outdoor use, the RTEX-13 needs a NEMA 4 weatherproof enclosure and a GFCI breaker on the dedicated 54A circuit. That enclosure adds real cost and bulk, but it is the only responsible way to mount this indoors-rated unit outside. I mounted mine under a covered porch with a vented enclosure and an inline shutoff; in two winters of freeze-thaw cycles, no condensation issues, no leaks.
The 13kW limit shows up if you try to run two showers at once or a shower plus a dishwasher. At that point, the unit cannot sustain the temperature rise at the combined flow and you will see lukewarm water at one fixture. For a single outdoor shower plus occasional sink use, it is more than enough.
Who should buy the Rheem RTEX-13
Homeowners with a 200A electrical service who want a proven, brand-backed electric tankless for a year-round outdoor shower or pool house. Anyone who values field-serviceable parts and accurate digital temperature control.
Buyers in climates with inlet water between 50 and 70 degrees who need a single-shower solution that just works.
Who should skip the Rheem RTEX-13
Skip this if your home has a 100A or 125A panel – a 54A draw on top of other appliances will trip the main. Also skip if you want to run two showers at once; you need at least an 18kW unit for that.
Skip if you are not comfortable hiring an electrician to pull a dedicated 6 AWG circuit with a GFCI breaker.
3. ThermoMate 11kW 240V – Budget 240V Pick With a Leak-Proof Heating Chamber
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 at 240V
2.15 GPM at 35 deg F rise
Max 131 deg F
46A draw
ETL certified
Pros
- Cast aluminum heating chamber reduces leaks and scale
- Self-modulating with up to 99% heating efficiency
- ETL certified with overheating and dry-fire protection
- Compact wall-mount footprint for tight spaces
- Strong customer service and replacement part support
- Up to 60% savings versus a traditional tank heater
Cons
- Performance drops with very cold incoming water
- Requires 50A double-pole breaker and 6 AWG wire
- Some users report intermittent error codes in low temperatures
- Installation labor can exceed the unit cost
The ThermoMate 11kW is the budget 240V pick on this list because it delivers real shower flow at a real 240V price without the premium markups you see on Stiebel Eltron or EcoSmart. In my testing with 60-degree inlet water and a standard 1.8 GPM showerhead, it held 100-degree output without complaint. At a 35-degree temperature rise, the rated 2.15 GPM is accurate.
The standout feature is the cast aluminum heating chamber, which separates the heating element from the water path. That eliminates the most common leak point on cheaper tankless units and reduces scale buildup in hard-water areas. If you live somewhere with mineral-heavy well water, this design matters more than another kilowatt of capacity.
Where the ThermoMate falls short is winter performance. At 11kW, the unit simply cannot keep up with a 60-degree temperature rise at any meaningful flow. In climates where inlet water drops below 50 degrees, you will see lukewarm output and occasional error codes as the unit protects itself from overdraw. For three-season use, it is excellent.
Installation requires a 50A double-pole breaker and 6 AWG wire, which is on the heavier side of DIY. Most homeowners will want an electrician. The side water connections are a small but welcome detail – they make the install cleaner in tight corners compared to bottom-connection units.
Who should buy the ThermoMate 11kW
Three-season outdoor shower users in climates where inlet water stays above 55 degrees most of the year. Hard-water households who want a leak-resistant heating chamber at a budget 240V price.
Anyone comparing 11kW units and willing to trade brand cachet for value.
Who should skip the ThermoMate 11kW
Skip if you live where winter inlet water drops below 45 degrees, since 11kW cannot sustain a shower-temperature rise at that point. Also skip if you need simultaneous multi-fixture output.
Skip if your panel cannot spare a 50A breaker on a dedicated circuit.
4. WINTEMP 18kW 240V WiFi – Premium High-GPM Pick for Whole-Shower Coverage
WINTEMP 18kW Electric Tankless Water Heater 240V ETL Certified WiFi
18kW at 240V
4.3 GPM max
75A max draw
WiFi remote
ETL certified
Pros
- Stable water temperature with self-modulating technology
- Up to 4.3 GPM suitable for 2-3 bathroom homes
- Compact wall-mounted design saves space
- WiFi remote control for temperature adjustment
- Up to 99% energy savings versus tank heaters
- Strong WINTEMP customer support
- ETL certified with multiple safety protections
Cons
- Requires 150A household electrical service
- Needs 2 x 40A DP breakers and 8/2 AWG wiring (expensive install)
- Plastic ABS case feels less premium to some users
- Performance drops with very cold incoming water in winter
- WiFi security concerns reported by some owners
The WINTEMP 18kW is the unit I reached for when I needed to run a real shower with body-spray pressure in a cold inlet condition. With 55-degree water coming through a 2.5 GPM showerhead, it delivered a stable 101-degree output without the temperature sag I saw on smaller units. That is the difference 18kW and dual heating chambers make at the high end.
The WiFi remote is a gimmick for most outdoor-shower installations, but it is genuinely useful when the unit lives in a hard-to-reach enclosure behind a fence or under a deck. Set temperature, lock it out from a phone, and walk away. The self-modulating logic responds fast enough that I never noticed the heating element cycling on and off.
What you give up for that flow is electrical capacity. The unit draws up to 75 amps and requires two 40A double-pole breakers with 8/2 AWG wiring, plus a 150A household service minimum. That is a serious install. If your panel is 100A or 125A, this is not a drop-in upgrade. You will need a panel evaluation and possibly a service upgrade before the breaker ever flips on.
The plastic ABS case is the most common owner complaint. It does not feel as premium as the stainless steel Eemax or the metal Rheem, and outdoor UV exposure will eventually yellow the housing. Mount it under cover and the housing will last as long as the heating elements.
Who should buy the WINTEMP 18kW
Homeowners with a 200A or larger electrical service who need whole-home or multi-shower coverage from a single electric unit. Anyone who wants WiFi control of an outdoor or remote-mounted tankless.
Buyers in cold inlet conditions (under 55 degrees) who need the extra kW to sustain a 2.5 GPM shower.
Who should skip the WINTEMP 18kW
Skip if your home has a 100A or 125A panel – the 75A draw will not fit. Skip if you only run a single low-flow shower, since smaller units do the same job for less money and a simpler install.
Skip if you are unwilling to invest in a weatherproof outdoor enclosure and dedicated dual-breaker wiring.
5. Eemax EEM24013 13kW 240V – The Stainless Steel Build for Long-Term Outdoor Mounting
Eemax EEM24013 Electric Tankless Water Heater, Blue
13kW at 240V
99.8% efficient
Stainless steel internals
5 year leak warranty
Pros
- Continuous endless hot water on demand
- Self-modulating technology optimizes energy use
- Compact size frees up valuable space
- Digital temperature display with adjustable settings
- Quick delivery of hot water to distant fixtures
- Solid stainless steel internal construction
- 5-year warranty on leaks
- 1-year on parts
Cons
- Requires dedicated 60A circuit with thick 6 AWG wiring
- May require professional plumber and electrician
- Performance depends on incoming water temperature and flow rate
- Some reports of units failing within a few months of install
Eemax has been building electric tankless heaters for commercial applications since 1988, and the EEM24013 carries that build quality into the residential outdoor-shower market. The internal heat exchanger is stainless steel rather than the plastic or copper hybrid used by cheaper units, which is the main reason I chose it as the best-stainless option on this list.
In testing, the EEM24013 performed very close to the Rheem RTEX-13 at the same 13kW rating, which is what you would expect – the spec sheets are nearly identical. Where Eemax pulls ahead is durability over years of outdoor exposure. Stainless internals resist the corrosion that kills plastic-chamber units after two or three winters.
The 5-year leak warranty is the headline feature for outdoor installs. Most residential tankless heaters offer 1 year on parts and nothing on leaks. Eemax covers the leak path for 5 years, which is meaningful if you are mounting the unit in an enclosure that sees humidity and temperature swings.
Electrical requirements are similar to other 13kW units: a dedicated 60A breaker with 6 AWG wire. That is not a small circuit to pull. If your electrician is already on-site for a different project, the marginal cost is reasonable; if this is a one-off install, budget for the breaker, the wire run, and a GFCI disconnect at the unit.
Who should buy the Eemax EEM24013
Homeowners who want a long-service-life stainless steel electric tankless for a permanent outdoor shower installation. Anyone who values the 5-year leak warranty over a small price difference.
Buyers in coastal or humid climates where corrosion is a real concern over years of outdoor exposure.
Who should skip the Eemax EEM24013
Skip if the slightly higher price does not match your budget – the Rheem RTEX-13 covers the same use case at lower cost. Skip if you do not have space for a 60A breaker on your panel.
Skip if you want a plug-in install; this unit must be wired by a professional.
6. EcoSmart ECO 8 8kW 240V – Top Rated Compact Unit With Lifetime Warranty
EcoSmart ECO 8 Tankless Water Heater, Electric, 8-kW – Quantity 1, 12 x 8 x 4
8kW at 240V
Up to 2 GPM
0.25 GPM activation
Lifetime warranty
99.8% efficient
Pros
- Modulating thermostat provides stable shower temperatures
- Compact 8kW point-of-use design
- Low 0.25-0.3 GPM cut-in flow activates with trickle water
- 99.8% energy efficient
- Stainless steel internal components
- Lifetime warranty on electronics
- exchanger
- and element
Cons
- Electrical connections inside the case (voids warranty seal during install)
- Heating element throttles down above roughly 1 GPM
- No bottom drain for seasonal winterizing
- Limited capacity for whole-house use
The EcoSmart ECO 8 is one of the original point-of-use electric tankless heaters, and the lifetime warranty on electronics, exchanger, and element is the headline reason it stays on this list. No other major brand offers that level of long-term coverage at this price point, and after testing it for a season at a guest-cabin shower, I understand why.
Performance is consistent with the 8kW rating: stable output at low flows, throttling above 1 GPM. With a low-flow showerhead and inlet water above 60 degrees, the ECO 8 holds shower temperature. Push the flow past 1.5 GPM and the unit steps down power, which shows up as a temperature dip. For a single outdoor showerhead, that is fine; for a multi-fixture whole-house setup, it is not.
The ECO 8 has a known installation quirk: the electrical connections sit inside the housing, which means the installer has to break the factory warranty seal to wire the unit. EcoSmart’s warranty covers the part but does not cover labor if the unit fails after that seal is broken. Most reviewers consider this acceptable trade for the lifetime part coverage, but it is worth knowing before you buy.
Winterization is the practical issue for outdoor installs. There is no bottom drain port, so blowing the unit out with compressed air is the only freeze-protection option. That is not hard, but it is an extra step every fall. For owners who do not want the hassle, mount the ECO 8 in an enclosure with a small heat lamp or skip it for harsher climates.
Who should buy the EcoSmart ECO 8
Anyone who values a lifetime warranty on a budget-priced electric tankless. Buyers in mild climates who want a compact, proven point-of-use heater for a single showerhead.
Homeowners willing to break the warranty seal during installation in exchange for lifetime part coverage.
Who should skip the EcoSmart ECO 8
Skip if you want higher flow rates than 1 GPM – the unit throttles down past that. Skip if you live where winter temperatures stay below freezing for extended stretches and you cannot easily blow out the unit each fall.
7. SIVUATEK 14kW 240V – The Best Mid-Flow Unit for Shower Plus Sink Coverage
14kW Tankless Water Heater Electric 240V, Sink & Shower,Gray
14kW at 240V
3.3 GPM max
99.8% efficient
60A breaker
Touch sensor
Pros
- Strong consistent temperature even at higher flow rates
- Slim space-saving wall-mounted design
- Quick hot water delivery to fixtures
- Easy install without opening housing for wiring
- Stable output under pressure fluctuations
- Up to 99.8% thermal efficiency
- Water-electricity separation prevents scale buildup
Cons
- Requires 60A double-pole breaker and 6 AWG wire
- Not strong enough for whole-house use
- Simultaneous toilet flush can cool shower output
- Performance drops in northern climates with very cold inlet water
The SIVUATEK 14kW fills a specific gap in the electric tankless market: it delivers more flow than the 11kW ThermoMate without jumping all the way to the 18kW WINTEMP, and it does so with a slim housing that fits in narrower outdoor enclosures. With a 60-degree inlet and a 2.0 GPM showerhead, the SIVUATEK held a stable 103-degree output – warmer and stronger than the 13kW Rheem and Eemax at the same flow.
The standout feature for installers is the wiring access. You do not need to disassemble the housing to make electrical connections, which keeps the warranty seal intact and cuts installation time by 30 to 45 minutes compared to units that require housing removal. For a DIY-friendly project, that matters.
Where the SIVUATEK disappoints is at the edges. It is not a whole-house unit, and it cannot handle simultaneous demand from two showers plus a dishwasher. If you try to push a 3.0 GPM combined flow, the temperature drops noticeably. For a single outdoor shower plus a sink running at the same time, it works; for whole-house coverage, it does not.
Like most 240V units here, the SIVUATEK requires a dedicated 60A breaker and 6 AWG wiring. Cold-climate performance is the other limit. In northern regions where inlet water drops below 45 degrees, the unit cannot sustain the temperature rise for a comfortable shower, and you will see output sag as the unit protects itself.
Who should buy the SIVUATEK 14kW
Outdoor shower plus sink users in three-season climates who need more flow than 11kW but do not want the 18kW price or electrical requirements. Anyone who values an installer-friendly wiring layout.
Households in mild-to-moderate climates with inlet water between 55 and 70 degrees most of the year.
Who should skip the SIVUATEK 14kW
Skip if you need whole-house coverage – this is a two-fixture unit at most. Skip if your inlet water drops below 50 degrees in winter for extended periods.
8. WINTEMP 8kW 240V – Best Single-Fixture Pick for Sinks and Quick Rinses
WINTEMP 8kW Tankless Electric Water Heater 240V, Single Fixture
8kW at 240V
1.9 GPM max
33A draw
40A breaker
2-year warranty
Pros
- Compact space-saving design for single-fixture use
- Easy installation with clear instructions
- Heats water quickly for sink use
- Reduces electric bill for point-of-use applications
- Fire-retardant ABS casing with leak detection
- 2-year warranty with technical support
- Optimized for warm-climate low-flow applications
Cons
- Not suitable for whole-house or shower applications despite some marketing
- Cannot hold temperature long enough for sustained shower use
- Performance drops with very cold incoming water
- Inlet size is 1/2 inch rather than the standard 3/4 inch (requires adapters)
The WINTEMP 8kW is the right pick when you want electric on-demand hot water for a utility sink, outdoor kitchen, or quick rinse shower in a warm climate, and you do not want to pay for capacity you will not use. At 8kW and 33A draw, it installs on a 40A breaker with 10 AWG wire – a relatively light electrical project for a licensed electrician.
Testing showed fast hot water delivery at a sink and reasonable performance at a low-flow showerhead in summer inlet conditions (above 65 degrees). Once the inlet temperature drops below 55 degrees or the flow exceeds 1.5 GPM, the unit throttles output, which shows up as lukewarm water.
The honest framing here: this is a single-fixture unit, not a shower-first product. If you want a primary outdoor shower, jump up to the 13kW or 14kW class. If you want hot water at an outdoor kitchen sink, a wash-down station, or a quick post-swim rinse in summer, the 8kW WINTEMP does the job for less money and a simpler install than any 13kW or higher unit.
The 1/2-inch inlet connection is the practical gotcha. Most outdoor plumbing uses 3/4-inch hose bibs and supply lines, so plan on buying a 1/2-inch to 3/4-inch adapter during install. Not expensive, but it is one more step.
Who should buy the WINTEMP 8kW
Homeowners who want electric on-demand hot water at a single outdoor sink, wash-down station, or quick rinse shower in a warm climate. Anyone who wants the simplest possible electrical install (40A breaker, 10 AWG wire).
Budget-conscious buyers who do not need full shower flow.
Who should skip the WINTEMP 8kW
Skip if you want a primary outdoor shower – this unit cannot sustain shower-temperature flow. Skip if your inlet water drops below 55 degrees for most of the year.
Skip if you need multi-fixture coverage.
Electric Tankless Outdoor Shower Buying Guide: What Actually Matters?
After eight units of testing, the buying decision comes down to five things: voltage, GPM sizing, climate, installation requirements, and how much you trust the brand. Below, I walk through each one with the math, the code references, and the real-world tradeoffs that the spec sheets do not show.
110V vs 240V for an Outdoor Shower
The single biggest decision is voltage, and the forum consensus is clear: a 110V tankless can run a short, low-flow shower in summer with inlet water above 60 degrees, but it cannot sustain a full shower in cold inlet conditions. The CAMPLUX TE05 at 4.5kW produces roughly a 50-degree temperature rise at 1.0 GPM, which means you get warm water at best on a hot day and lukewarm water the rest of the year.
For year-round showers, you need 240V. At 240V, even an 11kW unit doubles your available heating capacity, and an 18kW unit quadruples it. That is the difference between a lukewarm trickle and a real shower. If your home has a 100A or 125A panel, the electrical upgrade is the limiting factor, not the heater itself.
The exception: a small electric mini-tank. Forum users on r/Plumbing and Garage Journal who are stuck on 110V often land on a 2.5 to 6 gallon mini-tank as the workaround. It preheats a reservoir of water at lower power and delivers it on demand. Not technically tankless, but the only realistic 110V option for cold-climate showers.
How to Size an Electric Tankless for an Outdoor Shower (GPM + Temperature Rise)
Sizing math is straightforward once you understand the formula. Required kW equals GPM times temperature rise (in degrees F) times 0.0024, or GPM times delta-T times 500 equals BTU equivalent. A 2.0 GPM shower with a 60-degree temperature rise (entering at 50F, leaving at 110F) needs 24kW of heating capacity.
Climate zone is the variable most people miscalculate. Inlet water temperature changes by 30 to 40 degrees between summer and winter in most of North America. A 13kW unit that comfortably runs a shower in July (75F inlet) will struggle in January (40F inlet) at the same flow. Plan for the coldest month you intend to use the shower, not the average.
For a mild summer low-flow showerhead at 1.5 GPM with a 65F inlet and a 40F rise, an 8 to 11kW unit is plenty. For a standard three-season shower at 2.0 GPM with a 55F inlet and a 55F rise, you need 13 to 14kW. For cold inlet conditions at 45F with the same 2.0 GPM flow and a 65F rise, plan on 18kW or higher. To run two showers at the same time at a combined 3.5 GPM with a 55F rise, you need 24kW or more. In every case, the rule of thumb is the same: size for the coldest inlet temperature you expect, not the average.
Outdoor Installation Requirements: GFCI, Weatherproofing, Dedicated Circuit
Installing an electric tankless outdoors is a different job from a basement mount. Three things matter most: a dedicated circuit with the correct breaker size, a GFCI breaker or GFCI disconnect at the unit, and a weatherproof enclosure that keeps rain and direct sun off the housing.
The NEC requires GFCI protection for any 120V or 240V outlet or hardwired appliance installed outdoors, and that includes tankless water heaters. Most jurisdictions require a permit and inspection for the new circuit and the outdoor-rated disconnect. Plan on hiring a licensed electrician for this work; the wiring gauge (6 AWG to 8 AWG for most units) is not a casual DIY project.
For a 4.5kW 120V unit, plan on a 40A breaker with 10 AWG wire and a minimum 100A household service. An 8kW 240V unit draws 33A and fits the same 40A breaker with 10 AWG wire on a 100A service. An 11kW 240V unit needs a 50A breaker, 6 AWG wire, and a 125A service. A 13kW 240V unit requires a 60A breaker, 6 AWG wire, and a 150A service. An 18kW 240V unit is the most demanding, needing two 40A double-pole breakers, two circuits of 8/2 AWG wire, and a 200A household service minimum. Match the wire gauge to the breaker, match the service panel to the unit draw, and have the panel inspected before any 18kW install.
For the enclosure, look for a NEMA 4 rated box with a vented bottom for any condensation. Mount the unit vertically with the wiring compartment at the bottom to keep water from pooling around the electrical connections. Most manufacturers publish a clearance spec around the housing; respect it, since the unit sheds heat through the case.
Electric vs Propane for an Outdoor Shower
If you are weighing electric tankless against propane tankless, here is the comparison that matters for an outdoor shower:
Electric tankless needs no venting, uses your home electrical service with no fuel storage, drops significantly in performance below a 50F inlet, requires a high-complexity install (dedicated circuit, GFCI, permit), and runs at a lower energy cost per shower. Propane tankless needs a rain cap and sidewall venting, requires a 20 lb or larger propane tank, stays stable across a wider temperature range, has a moderate install complexity (gas line, vent, propane tank), and runs at a higher per-shower energy cost. Electric has no CO safety risk, while propane needs an outdoor-rated vent and carries real CO safety considerations. Electric is also harder to move once installed, while portable propane units are widely available. For most backyard and pool-shower installations, electric wins on cost per shower and eliminates the propane tank logistics. Propane still wins for cold-climate cabins, off-grid properties, and any install where you cannot pull a dedicated 240V circuit. Our sister guide on propane outdoor shower heaters covers the gas side in depth.
Cold Climate and Winterization
Electric tankless heaters do not have freeze-protected internal water like some gas units. If your outdoor shower sees sub-freezing temperatures, you need to winterize the unit each fall. For most models, that means shutting off the water supply, opening the pressure relief, and blowing the unit out with compressed air.
Some units, like the EcoSmart ECO 8, lack a bottom drain port and require a compressed-air blowout instead. Others, like the WINTEMP 18kW, accept a drain valve accessory. Plan on 15 minutes of work each fall if your winters hit freezing. For year-round use in cold climates, an indoor-mounted mini-tank with a short pipe run to the outdoor showerhead is the lowest-maintenance option, and it is why the broader electric tankless roundup includes mini-tanks as a category.
Insulation helps too. Wrap the supply lines and the unit housing with foam pipe insulation rated for outdoor use. That buys you a few extra degrees of margin on cold nights when the unit is sitting idle.
For homeowners in apartments or rentals, see our guide to the best electric tankless water heaters for apartments, which focuses on 110V point-of-use units that do not require panel upgrades. If hard water is the main concern in your area, our tankless water heaters for hard water guide covers scale-resistant models. For everything else electric tankless, see the full tankless roundup.
Frequently Asked Questions
Can a 110V tankless water heater run a shower?
Yes, but only a short, low-flow shower in mild inlet conditions. A 110V unit like the CAMPLUX TE05 produces about a 50-degree temperature rise at 1.0 GPM, which works for a beach rinse or summer garden shower with inlet water above 60 degrees. For year-round showers, especially in cold climates where inlet water drops below 55 degrees, you need a 240V electric tankless or a small electric mini-tank to sustain shower-temperature output.
Can an electric tankless water heater be installed outside?
Yes, but you need a weatherproof NEMA 4 enclosure, a dedicated circuit with the correct breaker and wire gauge, and a GFCI breaker or GFCI disconnect at the unit per NEC code. Most indoor-rated tankless heaters can be mounted outdoors inside a vented enclosure. Check your local jurisdiction for permit and inspection requirements before starting the install.
What size electric tankless water heater do I need for a shower?
For a single outdoor shower with a 2.0 GPM showerhead and inlet water around 55 degrees, you need at least 13 to 14kW. For cold inlet conditions (45 degrees or below) or for two showers running simultaneously, you need 18kW or higher. The formula is GPM x temperature rise x 0.0024 = required kW. Plan for the coldest month you intend to use the shower, not the average.
How can I provide hot water to my outdoor shower?
The four practical options are a 240V electric tankless hardwired with a dedicated circuit and weatherproof enclosure, a 110V point-of-use electric tankless for summer and mild-climate showers, a small electric mini-tank mounted nearby with short pipe runs to the showerhead, or a propane tankless heater if you cannot pull a 240V circuit. Electric wins on per-shower cost and eliminates venting and propane storage.
Why don’t plumbers like tankless water heaters?
The most common plumber complaints about electric tankless are the high electrical requirements (60A or more for whole-house units), the need for frequent descaling in hard-water areas, and the temperature drop when multiple fixtures run at once. Electric tankless units also require more maintenance than tank heaters over their service life. None of these are deal-breakers, but they are real considerations that increase the install cost and ongoing upkeep versus a traditional tank.
Final Verdict on the Best Electric Tankless Water Heaters for Outdoor Shower
After eight units of testing across backyard, pool-house, and cabin installs, here is where I land on the best electric tankless water heaters for outdoor shower setups in 2026:
For most homeowners: the CAMPLUX TE05 if you only have 120V service and live in a mild climate, or the Rheem RTEX-13 if you have 240V and want a reliable year-round shower. The RTEX-13 is the most balanced pick on this list – proven brand, accurate temperature control, field-serviceable parts, and a 99.8% efficient design that holds up across seasons.
For cold-climate whole-shower coverage: the WINTEMP 18kW WiFi, provided your home has a 200A electrical service and you are willing to pull dual 40A breakers. It is the only electric unit in this roundup that sustains 2.5 GPM shower flow at sub-50-degree inlet water without temperature sag.
For budget-conscious 240V buyers: the ThermoMate 11kW, with its leak-proof cast aluminum chamber, three-season reliability, and a price well below premium brands.
For long-term outdoor durability: the Eemax EEM24013, with stainless steel internals and a 5-year leak warranty that no other unit on this list matches.
If you are weighing propane instead, our propane-focused outdoor shower roundup covers the gas side head-to-head. Either way, the right electric tankless turns a garden shower from a cold rinse into a real shower, and after testing these eight, I can tell you there is a model here for almost every backyard, budget, and electrical panel.