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Renewables & Energy Production

Zero Net Energy Homes | Energy Generation Options | Choosing an Energy Generation System | Region Specific Annual Carbon Emissions Per

Quick Facts

  • Before evaluating a home’s energy needs, reduce a home’s power needs through proper sealing and insulation of the building envelope and through installation of properly sized, high efficiency heating and cooling devices and home appliances
  • Thinking of home performance as a system (and acting accordingly) will save money by reducing energy needs, since a smaller (and cheaper) renewable energy system will be needed
  • Technologies such as solar thermal and geothermal heating can substantially lower heating and cooling costs without producing electricity
  • The extra cost for renewable electricity generation (compared to gas powered generation) can pay for itself over time since there are no fuel costs
  • Since many utilities pay homeowners for energy produced on their property by renewable energy, energy bills can have a net zero cost over the course of a year

Zero Net Energy Homes

reduce then produceAfter a home’s energy load is greatly reduced through energy efficiency application (i.e. weatherization and installation of downsized, high efficiency heating, cooling, lighting, and appliances), it can be possible to cover remaining energy needs with renewable generation systems such as solar thermal heating and solar photovoltaic electricity.  The result can be a highly energy-efficient home which consumes no net energy from the utility grid over the course of a year (since seasons balance energy use).  Such homes already exist and are referred to as “zero net energy.”  The “zero net energy” home is the concept behind the Strategic Plan of the CPUC which has set up funding and goals to substantially increase the numbers of zero net energy homes (new and existing) over the next several years.

Energy Generation Options

Most homes are tied to the electrical grid and receive electricity from power plants which are powered by a variety of sources, which have varying levels of pollution and carbon intensity.  Carbon intensity is determined by the amount of greenhouse gases released to generate a certain amount of energy.  Many homes also have access to natural gas lines or buy propane or fuel oil for heating purposes.

Methods of supplying energy to homes include fuel powered generators as well as myriad home scale renewable energy technologies including:

Solar

Wind

Geothermal

  • Electric: also called PV (photovoltaics), these panels generate electricity
  • Thermal: generally used to heat water used for domestic hot water and/or space heating applications
  • A turbine, usually mounted on a tower, produces clean electricity when the wind blows fast enough
  • Heat pumps can have coils run through the ground to capture natural cooling and heating from the earth’s thermal mass; geothermal heat pumps are more efficient than basic heat pumps in extreme climates, but they still use electricity to operate.

Choosing an Energy Generation System

Homeowners may want to produce electricity or energy for their own home for a variety of reasons.  The most prominent reasons are:

  • The desire or need to retain access to electricity in the case of power outages
  • The desire to reduce carbon emissions linked to household energy use

Traditional generators can produce electricity anytime, but they consume fuel. A renewable system will need a battery backup to provide electricity during a power outage.

When choosing a home energy source to lower carbon emissions, it is important to keep the following considerations in mind:

  • The carbon emissions of the local electricity source
  • The carbon emissions of the home energy generation sources available
  • The payoff period of the home energy generation sources being considered
  • The payoff period for heat generating energy sources (which do not generate electricity), such as solar thermal and geothermal, including price of heating fuel and heating load for the home
  • Baseline electricity usage or heating load of the household (to size the system)

When choosing a home energy source for backup power in the case of power outages, it is important to keep the following in mind:

  • A battery is necessary to use renewable energy as a backup to the power grid (and will incur substantial additional cost and maintenance)
  • The carbon emissions of the energy source
  • The payoff period of the system, including cost of fuel if applicable
  • The baseline electricity usage of the household (to size the system)

Region Specific Annual Carbon Emissions Per MWH of Electricity

Carbon emissions from electricity vary with the local energy source.

Annual Carbon Emissions by Electric Energy Source

Energy Source kg CO 2 per MWh *
Coal 755-990
Gas 356-653
Solar PV 39-100
Nuclear 5-22
Wind 6-37
Hydro 3-23

* Range reflects a variety of scientific studies; Source: lightbucket .

Important Disclaimer
Product examples are for informative purposes only and mention of any product does not constitute a recommendation or endorsement of any product.