Can You Run a Tankless Water Heater on Solar?

Tankless water heaters are lauded for their energy efficiency, but as more home builders and owners are transitioning to innovative energy sources, the question emerges of can you run a tankless water heater on solar power? The answer is yes, but it depends on your configuration. 

According to the U.S. Department of Energy, installing a solar water heater can cut water heating costs by 50% to 80%, shielding you from future energy price spikes. The numbers only prove that solar energy is a futureproof investment that’s more energy efficient and saves you money in the long run.

At Hydro Solar, we help home owners shift toward smarter, greener systems, including PV panels and solar hot water solutions. This article will walk you through what you need to know about solar hot water systems for your home.

Tankless Water Heater Setup 

There are many variables to consider if you’re thinking of running a tankless water heater on solar panels. Your choice of system (solar photovoltaic (PV) or solar thermal) will dictate how everything connects and performs, so it’s not a decision to take lightly and requires thorough research in advance. 

A PV system converts sunlight into electricity to power an electric water heater, where solar thermal systems use the sun's heat directly to warm water. If you decide to use solar electricity, you’ll need to size your system appropriately. For thermal, you'll need a quality solar collector, like the vacuum tube solar collector kit, and a compatible tankless heater setup.

Electric Models Pair Well with PV Panels

PV panels can offer a straightforward solution for homeowners using an electric tankless heater. A properly configured solar electric system generates enough AC power to meet your tankless unit’s needs. When paired with a battery bank, this system can support consistent hot water even during cloudy days or peak hours. As energy demands fluctuate, having smart inverter control and an off-grid battery helps maintain water temp without depending solely on conventional energy sources. 

If you’re new to solar, our guide on how solar water heating works walks you through the fundamentals of solar-powered efficiency.

Mind the Power Requirements

Electric tankless units are convenient, but they come with high power demands. A single unit might draw up to 150 amps at peak usage. That means your PV system should be sized to at least 10kW, with an inverter that can manage those bursts without lag. 

It’s extremely important to match inverter capacity to the unit; otherwise, your flow rate or temperature may fluctuate during use. If your home already uses electric water heaters, you should consider upgrading your solar storage and inverter controls to ensure your tankless heater performs at its best.

Check out our article on solar water heater tank sizing to learn more.

Hybrid Systems Offer Flexibility

If your budget or rooftop can't support a large solar array, combining a gas tankless heater with a smaller PV system is a smart compromise. With a hybrid setup, solar energy offsets smaller loads in the house (like lighting and small appliances) while the gas heater makes sure that you have consistent water flow. 

It’s especially useful to have this kind of flexibility in colder climates, where winter sunlight is limited and backup energy is important. The tankless gas unit kicks in only when needed, allowing the solar system to handle the baseline load and reduce overall consumption.

Solar Thermal Can Preheat Water

If none of the other above options work for your home, you may consider integrating solar thermal with your tankless setup. This method preheats incoming water before it reaches the tankless unit, reducing the energy needed to bring water up to temperature. It improves efficiency and shortens lag during water flow. 

Adding a heat exchanger or mixing valve can fine-tune output and prevent overheating for those using a storage tank. By reducing the delta between cold water and final output temp, you save energy and extend the life of your tankless system.

Sunlight and Geography Impact Performance

Don’t overlook your environment. The success of any solar-powered system hinges on sun exposure and roof angle. 

In Canada, a south-facing roof and seasonal adjustments to flow control can make all the difference. During winter, you'll want to ensure proper drainage and freeze protection for any solar collector or small tank used in the system. 

Wherever you live, your system’s efficiency depends on proper maintenance and installation.

Make the Switch with Confidence

Adopting solar energy for heating water can lower monthly energy bills,and increase your home's energy independence. With the right system in place, you're no longer at the mercy of rising fuel costs or utility rate hikes. 

Solar setups also offer lower maintenance compared to conventional systems and reduce your carbon footprint. If you’re looking to replace an aging water heater or building a new eco-friendly home, using solar energy just makes sense.

Hydro Solar Has What You Need

Hydro Solar brings together top-tier solar technology with practical expertise, helping customers navigate the transition from traditional energy to solar-powered living. From Hybrid PVT panels to tailored setups that combine tankless units with solar hot water, we guide you through every step. 

Ready to ditch high energy bills and uncertain grid power? Contact us to learn how you can build a high-performance solar water heating system customized for your home or building.