"If you can take some of that global warming potential away by using natural refrigerants inside and then if you make it use less power to do that, then you've got a two-fold benefit to the end user."
Organic food supplier Ceres has joined a list of businesses, from dairy farms to coolstore owners, which have turned to EcoChill. "Our customer base is pretty wide and varied," says Darby. "Really, anyone who needs refrigeration."
Ceres is about to start work on a new distribution centre and is aiming to gain Green Star building accreditation - proof that it meets certain environmental standards.
"By default, refrigeration doesn't help you get Green Star accreditation because there is nothing green about it, whereas the EcoChill system can help," says Darby.
The company takes components made overseas, assembles them into its own designs and writes the software to run the systems, all with an eco-friendly twist.
Formerly known as Arneg, until a couple of months ago the EcoChill name branded one of the products the company developed. "I started to realise that EcoChill was more about what we are trying to do than simply one piece of equipment."
The fresh approach to refrigeration has seen EcoChill grow in a market dominated at one end by overseas-owned firms, and at the other by New Zealand owner-operators.
In an economic environment where companies are more cautious about spending money, Darby says the discerning buyer has emerged. "There is more consideration to 'what's my ongoing operating cost?' and that is where people are prepared to invest a little more upfront for reduced operating costs."
Until a decade ago Darby was employed by Kooline, a New Zealand-owned company not too dissimilar from EcoChill today, where he completed his refrigeration apprenticeship. Then Kooline's New Zealand owners sold the business to multinational conglomerate Tyco.
Darby was told it would be business as usual but when his name disappeared off the payslip, replaced by a number, he knew it was time to move on.
Dipping into his savings, the then 27-year-old and a mate climbed into their vans and started doorknocking potential customers.
His first big client was secured when Darby paid for a $180 Friday-night taxi trip, from a mate's housewarming, via home for his tools, to sort out an on-site problem. The customer was impressed that he showed up and is still with EcoChill today.
His mate has moved on, but taking his place are brother James and father Michael, both qualified refrigeration engineers.
Rounding out the family connection, sister Louise joined the firm early on to sort out the admin side. The company now employs 34 staff in Auckland, Hamilton and Christchurch,
"I'm incredibly proud of the people we have attracted here and the people we've turned out too."
Darby says there is a huge opportunity for EcoChill in the New Zealand market and doesn't rule out taking a leap overseas when the time is right. "The last thing I want is another Tyco-type situation.
"We want to have a sound, New Zealand business that is exporting a good product supplying both local and international markets with EcoChill."