INSTASHOWER ULTRA
66K BTU RV Tankless Water Heater with Mixing Tank
$658.99
$819.99
Save $161.00
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More stable hot water from startup to shower.
InstaShower Ultra combines 66,000 BTU output, up to 3.9 GPM flow and a built-in mixing tank designed to reduce cold-water interruption. Segmented combustion targets steady outlet temperature. Heater-only package for owners reusing a compatible existing access door or choosing one separately.
View all features ↓66,000 BTUHigh-output propane water heating
Up to 3.9 GPMFlow for showers and daily use
±1°FTemperature stability target
0.5 GPMLow-flow burner activation
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More options available at checkout
30-day returns
Free contiguous U.S. shipping
2-year warranty
Choose your InstaShowerCompare all models
Fit and installation
- Exterior access door
- Exterior door not included
- Fuel
- LP propane
- Electrical supply
- 12V DC
- Water flow
- 0.5–3.9 GPM
- Altitude
- Up to 9,800 ft
- Size
- 17.6 × 14.3 × 17.6 in
- Weight
- 26.9 lbs / 12.2 kg
Heater-only package for owners reusing a compatible existing access door or choosing one separately.
What’s included
- ✓Water heaterInstaShower Ultra tankless unit
- !Exterior access doorHeater-only package for owners reusing a compatible existing access door or choosing one separately.
- ✓ControllerSmart wired controller
- ✓Safety valve150 PSI pressure relief valve
- ✓Product documentationInstallation hardware and user manual
Gas, water and electrical connection materials vary by RV.
Specifications
- Heat input
- 66,000 BTU
- Hot-water flow
- 0.5–3.9 GPM
- Temperature control
- ±1°F target
- Fuel
- LP propane
- Electrical supply
- 12V DC
- Maximum altitude
- 9,800 ft
Quick answers
Does this package include an exterior access door?
Heater-only package for owners reusing a compatible existing access door or choosing one separately.
What does the mixing tank do?
It buffers and blends water to reduce brief cold-water interruption when shower flow changes.
Does it need 120V power?
Controls and ignition use 12V DC; the burner uses LP propane. No 120V supply is required.
Recommended for your RV setup
Pair the water-heater upgrade with climate equipment matched to the RV roof and duct layout.
For non-ducted travel trailers and fifth wheels
InstaCool Ultra
+$1,299.99
$1,749.99
Add quiet rooftop cooling and heat-pump warmth with a standard non-ducted roof opening and 115V supply.
Check roof fit and options
For larger ducted RVs and cold-weather travel
InstaHeat 35K
+$799.99
$1,299.99
Add stronger propane heat through a furnace matched to the RV cabinet and central duct system.
Check furnace fit and options
InstaShower Ultra
$658.99
$819.99
Save $161.00
ULTRA HEATER · EXTERIOR DOOR NOT INCLUDED
Maximum-flow comfort for an existing compatible door
This heater-only InstaShower Ultra combines 66,000 BTU, up to 3.9 GPM, a built-in mixing tank and a ±1°F target for RVs using a compatible existing or separately selected exterior door.
66,000 BTUHighest heat input
Up to 3.9 GPMHighest flow in the range
Built-in mixing tankSmoother restart
±1°FTemperature-control target
Reduce the frustrating parts of RV showers
Ultra is not only a larger burner. Its water path and staged combustion are designed around temperature stability during real use.
BUILT-IN MIXING TANK
Restart with less cold-water shock
The internal pre-mix system blends water before it leaves the heater, reducing the brief cold interruption that can happen in an RV plumbing loop.
SEGMENTED COMBUSTION
Adjust the flame as conditions change
Lower flame staging helps reduce overheating in warm conditions, while the full burner supports colder inlet water and higher demand.
HIGHER FLOW
Add flow margin for frequent showers
Ultra provides the strongest flow platform in the range, with delivered flow shaped by inlet-water temperature and temperature rise.
WEATHER-READY OPERATION
Travel higher and through colder routes
Correct propane, ventilation, 12V power and winterization remain essential for safe operation.
WHO SHOULD CHOOSE ULTRA?
Ultra performance for an existing compatible door
This heater-only package brings the 3.9 GPM Ultra platform to RVs with a compatible, serviceable exterior door.
A strong fit for frequent showers and higher demand
The 3.9 GPM platform adds more headroom for couples and families who use hot water often.
The mixing tank is the main comfort difference
It is designed to reduce cold-water interruption when the shower stops and restarts.
Pair with a compatible exterior door
A compatible existing door provides the required size, exterior coverage, venting, hinge and latch condition.
Heater-only package for an existing compatible door
Reuse a compatible existing access door or pair the heater with a separately selected door; the heater fits a common 13 × 13-inch opening.
FIT AT A GLANCE
Door options for common RV water-heater openings.
Heater-only package for owners reusing a compatible existing access door or choosing one separately.
- Minimum clear opening
- 13 × 13 in
- Exterior access door
- Exterior door not included
- Fuel
- LP propane
- Electrical supply
- 12V DC
- Maximum altitude
- 9,800 ft
Choose from the actual cutout and exterior coverage; the installation manual covers venting, weather sealing and service access.
Choose the InstaShower flow and package
Choose Ultra for the 3.9 GPM platform and mixing tank when a compatible exterior door is already available.
InstaShower Ultra · Heater only
For maximum flow and tighter control when a compatible exterior door has already been confirmed.
- Heat input
- 66K BTU
- Flow
- Up to 3.9 GPM
- Comfort
- Built-in mixing tank
InstaShower 8 Pro
For regular shower use, up to 3.1 GPM and a ±1°F stability target.
- Heat input
- 60K BTU
- Flow
- Up to 3.1 GPM
- Best for
- Frequent use
InstaShower 8 Plus
For continuous hot water and everyday midsize-RV shower demand.
- Heat input
- 55K BTU
- Flow
- Up to 2.9 GPM
- Best for
- Everyday replacement
See Ultra performance and installation
Mixing-tank operation, full retrofit and owner performance in three practical videos.
▶FULL REPLACEMENT
See a tankless replacement from removal to startup
A complete installation walkthrough covering the opening, connections and first hot water.
▶TEARDOWN + TEST
See the mixing tank and burner before installation
An internal look at the parts designed to improve shower stability and service access.
▶OWNER EXPERIENCE
See why the mixing tank matters in normal use
A practical review focused on cold-water interruption and shower consistency.
Quick answers about the heater-only Ultra package
See how the heater-only package, 3.9 GPM platform and existing-door compatibility support the upgrade.
How does the mixing tank help?
It blends water inside the heater to reduce the brief cold interruption that can occur when an RV shower stops and restarts.
What affects maximum flow?
Ultra provides up to 3.9 GPM; delivered flow varies with inlet-water temperature, water pressure and the requested temperature rise.
Does this package include an exterior access door?
Heater-only package for owners reusing a compatible existing access door or choosing one separately.
What powers the controls and burner?
Controls and ignition use 12V DC; the burner uses LP propane. No 120V supply is required.
What does installation involve?
Standard RV water, LP propane, 12V, venting and weather-sealing connections. Use a qualified installer when local rules or experience require it.
Have a compatible door and want maximum-flow comfort?
Choose the heater-only package above. The installation guide is available for final fit planning.
This product is rated 5.0 of 5.0 stars.
It has received 20 reviews.