By Cala Systems | August 25th, 2025
Cala has reached an important milestone: our intelligent heat pump water heater is now ENERGY STAR® qualified and safety certified, conforming to UL Standards 60335-1, 60335-2-40, and 174.
For homeowners, contractors, insurers, utilities, and others in the building and energy sectors, Cala’s certifications are more than a technical milestone – it’s proof that a new era of home infrastructure is here. Cala has been independently validated to meet the highest standards of safety and performance, but the real story is bigger: years of design and testing are now becoming reality, with intelligence moving from the lab into real homes. This is where hot water stops being a background utility and starts becoming part of a smarter, more resilient, lower-carbon future.
Certification and why it matters
Certification is a formal mark of safety for products that comply with the standards established by Underwriters Laboratories (UL), the global leader in safety science. UL works with experts in each industry to write and update these standards over time, and products achieve certification by undergoing a rigorous design review and testing process with a Nationally Recognized Testing Laboratory (NRTL). For Cala, we worked with Intertek’s Electrical Testing Laboratories (ETL). ETL has deep expertise and a storied history going back to Thomas Edison’s Lamp Testing Bureau.
Cala – and some of its individual parts – required certification to multiple standards addressing different aspects of operation, including but not limited to:
- UL 174 Household Electric Storage Tank Water Heaters
- UL 60335-1 Household and Similar Appliances: General Requirements
- UL 60335-2-40 Household and Similar Electrical Appliances: Particular Requirements for Electrical Heat Pumps, Air-Conditioners, and Dehumidifiers
- UL 60730-1 Automatic Electrical Controls: General Requirements
Certification isn’t optional – it’s required by building inspectors, insurance providers, utilities, retailers and professional contractors.
All of these stakeholders know that the certification mark on the Cala heat pump water heater means Cala has been designed, tested and validated to the most rigorous safety and performance standards.
Why Certifying Cala Was Groundbreaking
Certifying a traditional heat pump water heater isn’t new. Certifying a heat pump water heater that customizes water heating for each home, each day – that’s entirely different.
Cala is a completely new approach to water heating. It combines innovative monitoring, external data, predictive controls, and precision hardware to continuously optimize when, how fast, and to what temperature the water is heated. With Cala, the heat pump water heater becomes an intelligent thermal battery. (Forbes recently spotlighted this aspect of Cala’s design in their piece on “super-smart thermal batteries.” Read more here.)
Certifying Cala required:
- Proving safety in a variable speed compressor: unlike fixed-speed systems, which run at a simple on/off setting, variable-speed designs rely on high-voltage power electronics managed by a sophisticated processor. That added complexity makes them much harder to design, build, and certify.
- Proving safety in autonomous water temperature control: the UL 174 standard for electric water heaters has specific requirements for safely managing water temperature in the tank. Cala’s innovative design complies with this standard while still enabling Cala to heat water to the optimal temperature for each home based on its specific needs and preferences.
Certificating Cala required over 15 months of design, testing, supply chain, and compliance work. Throughout this period, our hardware and software teams worked with suppliers, subject matter experts, and Intertek to systematically demonstrate that Cala delivers safe and reliable performance in both normal and abnormal conditions.
What is ENERGY STAR®?
ENERGY STAR® is the government-backed symbol for performance and energy efficiency, run by the U.S. Environmental Protection Agency (EPA). ENERGY STAR® qualified products are verified to use less energy and save homeowners money on their utility bills. Similar to certification, products achieve qualification by undergoing a rigorous test of performance under conditions designed to represent real water usage in your home. For water heaters, achieving ENERGY STAR® qualification is often required to qualify for utility and state energy efficiency program rebates.
For Cala, being ENERGY STAR® qualified means our water heater delivers the energy savings homeowners, utilities and energy efficiency program managers expect.
Why This Matters Beyond Installation
Cala’s certifications are more than a technical achievement, they’re a milestone for water heating, distributed energy, and intelligent appliances. We’re delivering the water heater of the future - one that learns, adapts, and integrates seamlessly with your life, your home, and the world outside to make them better.
Meeting the standards was required. Redefining how the heat pump water heater is designed - that’s what makes this a milestone. Now the standard is met, the future begins: shipping Cala.
