In 1948, engineer Avy Miller formed Laars Engineering as a company dedicated to the concept of heating water quickly by passing water through finned copper tube heat exchangers. Miller realized that moving water at high velocity through "low-mass" heat exchangers such as finned copper tubing could heat water up to nine times faster than through cast iron vessels. Miller designed specialized manufacturing techniques to support this new concept, and the "low-mass" technology found a warm reception in the U.S. market.
First applied to the swimming pool heater market that emerged rapidly in California after WWII, the heat exchanger designs that Laars developed also proved to work well with space-heating boilers and hot water boilers. After all, if a Laars heat exchanger could work well with swimming pool water which uses chemicals and contains impurities, it would work even better with clean domestic hot water and closed loop hydronic systems.