Everyone wants to save energy. The tough part is figuring out how to do it.

To that end, Perkins + Will, an architectural firm with a large focus on green, is publicly releasing an internal software tool that effectively sets parameters for reducing the overall greenhouse gas emissions and energy consumption of a particular building.

You plug in the energy consumed per square foot in  similarly situated buildings and the fuel mix (the percentage of coal, nuclear and renewables) in the geographic region where the building will be erected, and the e2 Energy Estimating Tool gives recommendations on reducing power consumption or supplanting traditional power with onsite or offsite green energy.

"It empowers architects to be able to ask for things," said Doug Pierce, the Perkins + Will senior associate who came up with it. "If we've got numbers and goals and metrics, the chances are much better that you will be able to accomplish something."

Building operations represent one of the prime areas for curbing greenhouse gases. Roughly 40 percent of the total energy consumed in the U.S. (and 76 percent of the electricity) goes toward keeping the lights, appliances and HVAC systems up and running in homes and office buildings – and many of these systems are not particularly efficient.

At the same time, reducing building power consumption is incredibly challenging. In commercial buildings, for instance, owners often aren't motivated to invest in energy efficiency because the tenants pay utility bills. In Chicago, several large office buildings are equipped with cheap, inefficient electrical heating systems. The vast majority of the homes in the U.S. were constructed during eras when energy bills weren't a concern (see Controlling Energy Consumption a Million Square Feet at a Time).

Additionally, green building revolves mostly around curbing power consumption by exploiting natural light or ambient air conditioning (see Eleven Cool Names and Concepts to Watch in Air Conditioning). It is less about producing energy with solar panels or small wind turbines. It might sound silly, but the importance of conservation at times has been overlooked because it involves not doing something versus replacing a fossil-fuel source.

The parameters for e2 dovetail with the goals set out in Architecture 2030, the net zero energy plan endorsed by the American Institute of Architects. Under it, the idea is to reduce energy consumption in buildings steadily over the next few decades until it's possible to economically build net zero energy buildings in 2030. Buildings slated for 2010, for instance, should consume only 60 percent of the energy of a contemporary building. In 2020, the goal will be to be able to erect buildings that consume 80 percent less power. (The data for average energy consumption of similar buildings comes from Energy Star databases.)

California's Arnold Schwarzenegger has also endorsed a plan to change state building codes so that homes will be net zero by 2020 and commercial buildings will be net zero by 2030.

Although it will vary by project, most of the energy gains from the tool will come from gains in efficiency, but it will also show how reductions can be made through adding onsite renewable power sources. The tool lets building owners count power generated under local renewable power standards, but power generated under RPS is discounted. In some states, the RPS standard includes hydroelectric power.

The tool does not take into account energy reduced by adopting green building materials. It also does not, as yet, calculate the cost savings possible by adopting more energy-efficient practices.

Join industry leaders and influencers at Greentech Media's Green Building Summit in Menlo Park, Calif., June 11.