CRAFTSMAN CMXTEPA0018 Electric Tankless Water Heater: Never Run Out of Hot Water Again!

For anyone who grew up in a house with a basement, there was a sound. It was a low, guttural rumble, followed by a resonant whoomph as the pilot light ignited the burner. It was the song of the beast in the corner—a hulking, cylindrical steel giant, swaddled in a thin layer of insulation. That giant was the tank water heater, a faithful, unquestioning servant that provided the comforting magic of a hot shower. For the better part of a century, it was the undisputed king of domestic comfort, a silent partner in our daily rituals. But it was a hungry king, and a wasteful one. And its reign is coming to an end.

The story of that familiar tank begins in the smoky, industrious twilight of the 19th century. As cities grew and a new middle class emerged, the demand for indoor plumbing and modern conveniences skyrocketed. A Norwegian mechanical engineer named Edwin Ruud, who had immigrated to Pittsburgh, saw a need. In 1889, he designed and patented one of the first automatic, gas-powered storage water heaters. It was a revolutionary idea: use a small, efficient flame to heat a large reservoir of water and keep it hot, ready for use at a moment’s notice. He was, in essence, canning heat. This “storage paradigm” was a brilliant solution for its time, and it fundamentally shaped the architecture and lifestyle of the 20th-century home.

But this century-old solution carries a hidden tax, a quiet penalty dictated by the unforgiving laws of physics. The culprit is the Second Law of Thermodynamics, which, in simple terms, states that heat naturally moves from a warmer place to a cooler place. Your 40- or 50-gallon tank heater, holding water at a toasty 120°F or more, is constantly at war with the cooler ambient air of your basement or utility closet. This ceaseless, silent escape of energy is called standby heat loss.

Think of your old water heater as a wooden bucket filled with water, but the bucket has dozens of tiny, invisible leaks. To keep it full, you must constantly add more water, whether you’re drinking from it or not. Similarly, your tank heater must periodically fire up its heating mechanism just to replace the heat that has bled away into the surrounding space. It’s working while you’re at work, while you’re on vacation, while you’re fast asleep. According to the U.S. Department of Energy, water heating is typically the second-largest energy expense in a home, accounting for around 18% of the average utility bill. A significant portion of that cost is simply paying to re-heat water that got cold while sitting around.

This is where a fundamental shift in thinking occurs, a move from the storage paradigm to an on-demand one. It’s a philosophy embodied by devices like the CRAFTSMAN CMXTEPA0018 18kW Electric Tankless Water Heater. This machine doesn’t store anything. It has no reservoir, no pilot light, no standby mode. It sits dormant and silent, consuming virtually no power until the exact moment you demand its service.

When you turn on a hot water tap, you’re not calling upon a reserve; you are issuing a command. A sensor detects the flow of water and instantly unleashes a controlled torrent of energy. The science behind this instantaneous warmth is Joule Heating, another fundamental 19th-century discovery. It dictates that running an electric current through a resistor generates heat. Inside the CRAFTSMAN unit, powerful heating elements act as these resistors. The system’s 18,000-watt capacity isn’t a measure of constant energy consumption, but a measure of its immense responsive power. It’s the equivalent of a car’s horsepower; you don’t use all of it while cruising, but you need it for immediate, powerful acceleration. The tankless heater is a miniature, dedicated power plant for your plumbing, capable of ramping up from zero to full output in a fraction of a second.

Now, this is the part of the story where a practical-minded homeowner might raise an eyebrow, a reaction echoed in many online reviews and DIY forums. To deliver that much power that quickly requires a robust electrical infrastructure—specifically, in this case, two 40-amp breakers and thick, 8-gauge copper wiring. Some see this as a flaw or an expensive hassle. In reality, it is an immutable consequence of the laws of physics. You cannot move a massive amount of electrical energy safely without a wide, clear path. The heavy wiring is not a product shortcoming; it’s an electrical superhighway built to handle the immense power required for instant comfort, ensuring safety and preventing a system meltdown.

This same physics-based reality governs the unit’s performance across different climates, another point of confusion for some users. The key metric is “temperature rise”—how many degrees the heater must raise the incoming water’s temperature. Imagine the heater’s effort level. In Miami, where the groundwater might be a mild 70°F, getting it to a 115°F shower temperature is a light jog—a 45°F rise. At that pace, the CMXTEPA0018 can sustain a healthy flow of 2.85 gallons per minute. But take that same unit to Montreal in January, where the water entering the house can be a bone-chilling 38°F. To reach the same 115°F, the heater is now in a full sprint, needing to achieve a massive 77°F rise. This intense effort means it can only heat a smaller volume of water at a time, reducing the flow rate. It’s not that the machine is weaker; it’s that the laws of thermodynamics are making it work significantly harder.

The transition from the rumbling beast in the basement to a sleek, wall-mounted digital unit is more than just an appliance upgrade. It reflects a profound evolution in how we think about resources, space, and time. We’ve moved from a philosophy of hoarding—storing vast quantities of energy and water “just in case”—to one of intelligent, lean, on-demand management. The space once occupied by that steel giant can now become a pantry, a workshop, or simply open space. The energy once wasted keeping water hot overnight can now remain in the grid until it’s truly needed.

The old tank water heater was a loyal servant, a product of an era of abundance and brute-force engineering. The CRAFTSMAN tankless unit, and others like it, represent a new kind of partner. It’s smarter, more efficient, and more attuned to the rhythms of modern life. It understands that the greatest luxury isn’t having a massive reserve of hot water, but the ability to create the perfect amount of it, endlessly, at the precise moment you desire. It’s a quiet revolution, happening right inside our walls.