What Is the Apparent eXeL Solar Water Heater and How Does It Work?

The Apparent eXeL is a hybrid solar water heater built by Apparent Inc., a company based in Novato, California. It's a pre-assembled system built from three parts: a custom stainless steel tank in 65 or 105-gallon capacities, a dedicated photovoltaic solar panel array with its own racking and wire harness, and a patented low-voltage DC heating assembly — a proprietary heating element paired with a smart controller. The panel array feeds that heating element directly, under 60VDC, so there's no inverter converting the power and no pump circulating fluid the way an older solar thermal collector system worked. The Otter Squad is an authorized installer of the eXeL in Livermore, and this page walks through what the system actually is, how it works, what an install involves, and who it fits.

The three parts, and why "no inverter, no pump, no refrigerant" matters

Most hot water systems homeowners already know fall into a handful of categories: a gas or electric storage tank, an electric tankless unit, a heat-pump water heater, or an older solar thermal collector system that circulates fluid through roof panels and a pump. The eXeL is a different design from all four.

Its PV panel array generates direct current electricity and sends it straight to the tank's low-voltage DC heating element, according to Apparent's spec sheet, with an input voltage range of 12.5 to 52VDC and a maximum DC output of 1,300 watts from the panel array. Because that power goes directly into the heating element as DC, the system doesn't need an inverter to convert it to AC first. And because the heat transfer happens through electrical resistance in the element itself, not through a fluid loop, the system doesn't need a pump to circulate anything or a refrigerant to carry heat the way a heat-pump unit does.

Fewer moving parts is the practical takeaway. No pump means no pump to fail. No refrigerant means no refrigerant line to leak or service. No inverter means one less component converting power and generating its own heat and wear along the way. That's a meaningfully simpler design than the solar water heaters homeowners from an earlier generation might remember, and it's a big part of what an authorized installer is trained to explain honestly — including where it still needs real maintenance.

What "no inverter, no pump, no refrigerant" does and doesn't mean for upkeep

Simpler wiring doesn't mean zero maintenance, and it's worth being precise about what the spec sheet actually supports. Per Apparent's documentation, the tank's titanium-encased heating element and stainless steel construction eliminate the need for a sacrificial anode rod, which is one maintenance item a standard tank water heater does require over its life. The system's DC protections include a 70VDC/50A fuse, and the electronics and heating element carry their own 2-year warranty separate from the tank's 8-year warranty and the panels' 10-year warranty.

What the fewer-parts design doesn't eliminate is the need for a working PV array, kept reasonably clear of debris and shading, and a working 110V AC backup circuit, since that circuit is what keeps hot water flowing on a cloudy stretch or overnight when the panels aren't carrying the full load. Those are the same categories of upkeep any electrical and plumbing system needs; the eXeL's design just gives fewer components inside that upkeep loop than an inverter-and-pump system would.

How the cloudy-day and grid-backup function works

Livermore gets more sun than a lot of the Bay Area, but no PV array runs at full output every day of the year. The eXeL's standard 110V AC grid backup is built into the system for exactly that gap. According to Apparent's materials, the backup connection takes over automatically whenever the panel array isn't generating enough DC power to fully carry the heating load, so the tank keeps producing hot water through overcast mornings, winter stretches, or overnight without any manual switching by the homeowner. That same backup circuit is also what makes the system capable of running fully off-grid if that's ever needed, since the tank isn't solely dependent on either power source to function.

The default factory temperature setting is 125°F, adjustable up to a 158°F maximum, with over-temp protection built in at 170°F plus or minus 5°F, per the spec sheet. A WiFi-enabled smart app lets a homeowner check tank temperature and monitor estimated energy savings from a phone. Apparent's own marketing cites savings of up to approximately 25% on the monthly water heating cost; that figure comes from Apparent, not from measurements The Otter Squad has taken on a specific Livermore home, and it should be treated as the manufacturer's claim rather than a guaranteed number for any one household.

What an eXeL installation actually involves

Because the eXeL ships pre-assembled, the install is more contained than building a from-scratch solar thermal system, but it's still real electrical and plumbing work. Apparent's own installation guidance recommends professional installation to meet code, not a DIY panel-and-tank kit. The steps below reflect that guidance alongside the standard scope for any water heater swap in Livermore:

• Site assessment. Roof orientation and pitch for the panel array's sun exposure, a mounting location for the tank rated for its weight (about 106 lbs for the 65-gallon tank, about 148 lbs for the 105-gallon tank, before it's filled with water), and the run length between the panel array and the tank.
• Tank sizing. Choosing between the 65-gallon and 105-gallon models based on the household's actual hot water demand.
• DC wire harness run. Connecting the panel array to the tank's low-voltage DC heating assembly, operating well under the system's 60VDC threshold, with the DC protections (a 70VDC/50A fuse) the spec sheet calls for.
• 110V AC backup circuit. Wiring the standard AC connection that powers the grid backup and the WiFi controller.
• Plumbing tie-in. Connecting the tank's 1-inch NPT inlet and outlet, rated to a maximum of 87 psi, into the home's existing water lines — similar in scope to a standard tank swap.
• Permit. Any water heater installation in Livermore needs a City of Livermore Building Division permit, pulled before the work starts, the same as any other water heater swap.

That's a lighter electrical scope in some respects than a heat-pump water heater sometimes needs, since the DC heating path runs off its own dedicated panel array rather than drawing continuously off the home's main electrical panel. It's still a system with real code requirements on both the electrical and plumbing sides, which is why Apparent's guidance points toward a professional install rather than a homeowner project.

Who the eXeL fits

A solar water heater isn't the right call for every roof or every household, and being honest about that is part of what an authorized installer's job actually is. The eXeL fits best where:

• The roof gets real sun exposure, since the panel array needs a mounting location with enough consistent sun through the year to carry a meaningful share of the heating load.
• The household wants an electric replacement path that doesn't add continuous draw to the home's main electrical panel — which matters most on a home with a smaller or already-tight panel, since the DC heating element runs primarily off its own dedicated array rather than the home's main circuits.
• The homeowner is replacing a gas unit and thinking about the 2027 Bay Area gas water heater rule. Under that rule, gas water heaters under 75,000 BTU/hr manufactured on or after January 1, 2027 have to meet a zero-NOx standard that most standard gas units can't meet, which is pushing a lot of Bay Area replacements toward electric options. The rule doesn't affect a gas unit already running in a home, and it stays legal to repair past that date; it only becomes a live decision once the current unit actually needs replacing. Full detail, including the amendment the Air District has proposed since the rule was adopted, is in our 2027 gas water heater rule guide.
• Off-grid or backup-capable hot water matters to the household, since the system's combination of a dedicated DC power source and standard AC backup lets it function without a full utility connection if that's ever needed.

Where a roof genuinely doesn't get enough sun, or a household's priorities point somewhere else, a heat-pump or tankless unit may be the better fit instead, and that comparison belongs in the same conversation, not a separate sales pitch.

Certifications and warranty

The eXeL is listed in the California Energy Commission's appliance database under model numbers ASH66 for the residential unit and ASH105 for the commercial size, both listed October 15, 2024. The system is built to UL 174:2004, the safety standard that also governs standard electric storage water heaters. Per Apparent's documentation, the warranty runs 10 years on the solar panels, 8 years on the water tank, and 2 years on the electronics — meaning the DC heating assembly and smart controller.

Why an authorized installer matters

A solar water heater is still a newer product category for most plumbing companies, and Apparent's own installation guidance points toward professional installation rather than a DIY kit, specifically because the system involves real electrical work at both the panel array and the tank, along with the plumbing tie-in itself. The Otter Squad is an authorized Apparent installer, meaning our crews are trained on the eXeL system specifically — its wiring, its mounting requirements, and how it integrates with a home's existing plumbing and electrical setup — rather than approaching it as a generic tank swap with extra parts bolted on.

That training matters most when a job doesn't go exactly to plan, whether that's a roof structure that calls for a different mounting approach or a sizing decision that depends on how much sun a specific roof section actually gets across the year. An installer who has done the manufacturer's training on this exact system is working from real knowledge of the product, not figuring it out on a homeowner's roof.

Get a straight answer for your home

Whether the Apparent eXeL fits your Livermore home comes down to your roof's sun exposure, your electrical panel, and what you actually want out of a water heater replacement. The Otter Squad installs the Apparent eXeL solar water heater in Livermore as an authorized installer, alongside water heater installation for tank, tankless, and heat-pump options, and will walk through which one fits your home honestly before recommending one over another. Call (925) 397-2271 for a straight answer on your specific home.