Keep the hot water on.
Stop tripping breakers.
WatterWise maintains your water heater at full power until your other loads begin to crowd the shore-power limit. Then WatterWise smartly eases your water heater out of the equation, just enough to keep the breaker on, and only for as long as required.
How it works
WatterWise sees how much of your shore-power budget the rest of the boat is using and gives the water heater exactly what's left — no more, no less.
Sees the whole boat
WatterWise watches how much shore power the rest of the boat is using, and watches the water heater itself — keeping the total inside your shore-power limit.
Other loads come first
WatterWise gives priority to everything else on the boat. Whatever capacity is left in your shore-power budget goes to the water heater — second by second, without any manual intervention.
Smooth and silent
Power adjustments to the water heater happen invisibly — no flickering lights, no buzzing fans, no surprises on board. And nothing to manage on your end: no switches to flip, no settings to tune, nothing to babysit.
Watches the voltage too
On a long dock cable, heavy loads pull shore voltage down. WatterWise eases off the water heater before that drop can stress anything else on board.
Your thermostat still calls the shots
WatterWise sits behind your water heater's existing thermostat — never replacing it. The thermostat remains the primary safety device, exactly where the factory put it.
On the same network as your chartplotter
WatterWise can join your NMEA 2000 bus, so the water heater shows up on your MFD like any other system on the boat. See its status from the helm — and turn it on or off from there too.
Live on your phone or laptop
Connect to the boat's WiFi and watch shore-power use, voltage, and water heater behavior in real time. Adjust your target on the fly.
Take the wheel when you want
Force the heater off for the night, or set a fixed power level regardless of budget. A slider on the dashboard puts you in charge — and switches back to auto whenever you're ready.
Wires into the existing run
A single in-line install between your breaker and the water heater. No new plumbing, no replacement parts, no boatyard time.
Built for boats
Designed around the realities of 120VAC shore power: long cable runs, voltage sag, neighbors on the same pedestal, and the breaker that always seems to trip when you're already in the shower.
- Shore power
- 120VAC, 30A target (50A planned)
- Heater compatibility
- Standard 120V resistive marine water heaters
- Existing thermostat
- Always stays in series — non-negotiable
- NMEA 2000
- Status reporting + MFD control (optional)
- Local control
- WiFi dashboard with live gauges and chart
- Sag protection
- Linear pull-down between configurable thresholds
- Temperature sensing
- Heatsink + future tank-probe support
Frequently asked questions
Does WatterWise turn my water heater off?
No. It reduces the heater's effective power smoothly so the total load stays under your breaker. Most of the time you'll never notice — the water still gets hot, just slightly slower while other loads are active.
Does my water heater's thermostat still work?
Yes. The thermostat stays in series with WatterWise, exactly where the factory put it. It's the primary safety device and we don't touch that.
Will it work on a 50A boat?
30A is the first target. 50A support is on the roadmap — the controller architecture handles it, the install hardware is what changes. Join the waitlist and tell us your setup.
Does this work for RVs?
Yes. The electrical setup is nearly identical: a 120V resistive water heater on a shore-power pedestal that trips when other loads pile on. We led with marine because that's where we live, but the problem and the fix work just as well in an RV.
Do I need NMEA 2000?
No. WatterWise runs fully standalone with a WiFi dashboard. NMEA 2000 is there if you want heater status on your MFD or want your chartplotter to be able to enable/disable the heater.
Is this UL/ABYC certified?
Not yet — we're working toward it. The current units are pre-production hardware undergoing testing. Waitlist members will get the first production-certified units when they're ready.
When can I buy one?
We'll email the waitlist when units are available. No date promises until the certifications are real.