Sustainability | Renewable Energy

Zero Net Energy Homes - CA leads the Way

Cottle NZE Home

California has an ambitious goal of making all new homes zero net energy (ZNE). This effort had its foundations with The Cottle Home, CA's first ZNE home.

As part of commencing the efforts towards zero net energy in California, One Sky Homes introduced The Cottle Zero Energy Home; which is the very first of its kind. The Cottle Zero Energy home was completed in 2012 in San Jose, CA, at a cost of $2.2 million. The Cottle ZNE Home features 30 6.2KW photovoltaic (PV) solar panels, solar water heaters for heating water, and a high-efficiency electric heat pump for HVAC.

More than the luxurious build of the home, its biggest selling point is its efficient use of energy. Generally speaking, one house in California will most likely consume energy worth over $100 monthly. On the other hand, with The Cottle Home, the energy consumption is $15 (or usually less, and only due to standard utility connection fees) monthly.

ZNE building construction in CA

The construction of The Cottle Home was the foundational part of the plan of transforming California into a more sustainable state; and it serves as an example for other states to develop similar initiatives. California has recently mandated that all new home construction must be zero net energy (ZNE).

All new commercial buildings in the state must be ZNE by 2030. For more information on CA's goal to make all new residential construction ZNE starting 2020, please see: More information on Ca's ZNE plan>>>

 "As spelled out in the California Energy Efficiency Strategic Plan, the state has ambitious goals for the development of zero net energy buildings. These include:

  • All new residential construction will be zero net energy (ZNE) by 2020.
  • All new commercial construction will be ZNE by 2030
  • 50% of [existing] commercial buildings will be retrofit to ZNE by 2030
  • 50% of new major renovations of state buildings will be ZNE by 2025.

In 2016, the Department of General Services issued these definitions of zero net energy:

  • ZNE building - An energy-efficient building where, on a source energy basis, the actual annual consumed energy is less than or equal to the on-site renewable generated energy.
  • ZNE campus - An energy-efficient campus where, on a source energy basis, the actual annual consumed energy is less than or equal to the on-site renewable generated energy.
  • ZNE portfolio - An energy-efficient portfolio in which, on a source energy basis, the actual annual consumed energy is less than or equal to the on-site renewable generated energy.
  • ZNE community - An energy-efficient community where, on a source energy basis, the actual annual consumed energy is less than or equal to the on-site renewable generated energy."   (FROM-

CA's ZNE Building Mandate

California's zero net energy building mandate may not be an easy feat, but the California state government is serious about such endeavor. One of their more specific goals is to create awareness about what zero net energy is, what the benefits of ZNE buildings are, and ultimately, to increase demand of ZNE homes from the public.

The CA state government is also aimed towards making sure that technological tools for ZNE homes are available, which will make the shift easier for all stakeholders. It is paramount to make sure that building codes and regulations are aligned with the policies for zero net energy.

Lastly, the state, and PG&E (the biggest utility in California), also provide incentives to trigger participation in state ZNE building programs from the public, and to ensure the achievement of the state's goal by 2020.

Benefits of ZNE buildings

A ZNE home (or commercial building) reduces space heating, cooling and water heating loads. More high-end insulation is required, along with air tight construction and advanced home air filtration and conditioning. Appliances in the home or building should also be of the highest efficiency that is affordable.

A ZNE home uses higher efficiency lighting. After the building has been made as energy efficient as possible, a PV system is installed to provide the electricity used in the building and offset electricity supplied by the utility, so the building produces as much energy as it consumes (a ZNE building can also produce more energy than it consumes - in which case, it's known as a plus-energy building).

Here is a snippet from about the benefits of zero energy homes -

"Zero energy homes are just like any home—except better. They are regular grid-tied homes that are so air-tight, well insulated, and energy efficient that they produce as much renewable energy as they consume over the course of a year, leaving the occupants with a net zero energy bill, and a carbon-free home.

A zero energy home is not just a “green home” or a home with solar panels. A zero energy home combines advanced design and superior building systems with energy efficiency and on-site solar panels to produce a better home. Zero energy homes are ultra-comfortable, healthy, quiet, sustainable homes that are affordable to live in."


A 2019 update to California's progress of ZNE building construction in the state can be found in this article from CNBC-

  • "In California most new homes and multi-family residential buildings up to three stories high will include solar rooftop panels beginning in 2020.
  • Net-zero energy homes can produce as much energy as they consume and are built to optimize energy efficiency through airtight construction of roofs, walls, windows and foundations.
  • The U.S. has an estimated 5,000 net-zero energy single-family homes today; California could add 100,000 a year."   FROM -

All over the world, a higher level of emphasis is being placed on environmental sustainability; as evidenced by the increase in efforts towards energy efficiency and green building. Building developers are in a constant search of new technologies with the promise of reducing the carbon footprint of buildings; and optimizing the use of available energy without causing harm to the environment. The state of California is one of a few places worldwide that is achieving this goal. This is best represented through California's ambitious goal of making all new residential construction zero net energy starting 2020.

Please also see these articles, which include details on ZNE buildings in other locations:

The Bullitt Center Seattle


The Greenest City District in Europe


Vaxjo, Sweden - passive building construction methods

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