Honolulu has been very successful in reducing electricity usage in a long list of city facilities we targeted in 2005, where we have installed energy-saving technologies. Our 28 "goal" facilities have steadily reduced their energy usage and are now 12.52 percent below their 2005 baseline.

But like any growing city, we have added new buildings and operations that provide needed services. They all require electricity. And some facilities, such as the new Ultraviolet Disinfection unit at the Sand Island Waste Water Treatment Plant, use enormous amounts of electricity. The disinfection unit, which destroys pathogens in treated wastewater, was mandated by the U.S. Environmental Protection Agency and State Department of Health, and uses about 1,000,000 kilowatt hours per month at a cost of $3.9 million per year. This facility is responsible for the largest single part of our increased energy consumption, but it is necessary to protect public health and safety.

While we can and do accomplish the task of reducing energy use in our existing facilities, it's important to realize that our continuing growth has made direct comparisons to total energy consumption in years past completely unrealistic. That would be like comparing a six-person family's annual spending on groceries to its spending in the years before two of the children were born.

The truth is that we must continue to become more efficient, and at the same time add electrical energy consumption when planned expansion and public protection require it. We're accomplishing those goals. In fact, seven city agencies or operations trimmed energy consumption by 6 million kilowatt hours since 2007, while the remaining agencies posted minimal increases.

The Department of Environmental Services — which is responsible for the Sand Island disinfection unit and other facilities that protect public health — accounted for nearly all the increase in power consumption during the two-year period. When excluding this agency's usage increase, overall city electricity consumption would have decreased by nearly 5.3 million kilowatt hours since fiscal year 2007.

The city is also using more biodiesel — 1.416 million gallons last fiscal year alone. The city also installed energy-efficient air-conditioners for the Fasi Municipal Building and Blaisdell Arena; turns off the air-conditioning in city buildings after designated hours; participates in the Honolulu Lights Out campaign every third Saturday of the month; purchased more hybrid vehicles; and has expanded the use of fluorescent lighting.

A common misconception is that electrical usage is a bad thing that should be eliminated. No one disputes the fact that we must find better and more environmentally friendly ways to produce electricity on O'ahu that do not depend on imported oil.

Electricity itself is a very good source of power for nonpolluting equipment and cost-efficient operations of mechanical systems. Electrically powered mass transit and electrically powered personal automobiles provide a clean, quiet and more efficient and environmentally benign solution to vehicles powered by fossil fuels. If electrical usage increased in direct proportion to the diminished use of fossil fuels, it would be a very good trade-off.

I remain totally dedicated to our sustainability goals outlined in our award-winning and nationally recognized 21st Century Ahupua'a plan. First unveiled back in 2005, our plan establishes a comprehensive vision for O'ahu's future, in which energy conservation and alternative energy production are key components. It also outlines the active projects, goals and accomplishments of every city department in their efforts to make their operations more sustainable. For example, we are installing a 100-kilowatt photovoltaic system at our Halawa baseyard.

There are many other solar array and energy conservation projects being planned for the near term. Our pending federal Electrical Energy Conservation Block Grant projects alone will save an additional 1.5 million kilowatts — and more than $265,000 in taxpayer money — each year.

We have a shared goal and a well-defined destination. To get there, we need in-depth understanding, cooperation and constructive contributions to the continuing discussion about our future.

Mayor Mufi Hannemann wrote this commentary for The Advertiser.