California Greenhouse Gas Reduction

Dennis Silverman

U. C. Irvine

Physics and Astronomy

November 2007



We analyze automotive and household contributions to CO2 greenhouse gases in California, since these contributions are under the control of individual drivers and homeowners.  We show that in Southern California, the household CO2 generation by electricity is equal to that of natural gas, through equal amounts for hot water heating and space heating.  We provide a simple strategy to reduce greenhouse gases from electricity and hot water heating by 25% at modest cost.  In an addendum we analyze the greenhouse gas emissions from each of the major electric utilities in the state.  In another addendum, we analyze the timeline of the contributions from 1990 to 2004, and show that on a per capita basis, California has already almost satisfied the Kyoto agreement.  On a total state basis, CO2 emissions have to be cut 22% by 2012 to satisfy Kyoto as desired by the US Mayor’s Climate Protection Agreement.

Data Source:

The California Statewide Residential Appliance Saturation Study, 2004.  Numbers have been rounded off to make the relative magnitudes easier to perceive, and any errors in the calculations are my own.

Total Electricity usage (all applications) per year for comparison:

            USA         12,000 kWh per capita

            California   8,000 kWh per capita

Short and Long Term Proposed Standards for Low Energy Usage

            A short term goal is to comply with the US Mayors’ Climate Protection Agreement for greenhouse gas reduction, which is to match the Kyoto agreement of a 7% reduction from 1990 levels by 2012.  Since total California greenhouse gases rose 15% from 1990 to 2004, this would be approximately a 22% reduction.  A long range goal is a reduction to a sustainable production of carbon dioxide which is only 20% of the current rate.  A goal of 80% GHG generation below 1990 levels by 2050 has been set forward in Executive Order S-3-05 by Governor Schwarzenegger.  It is also considered a goal by some European organizations.  It would be far better for reducing global warming to achieve this in any energy use component as soon as possible, or when a new or replacement system opportunity occurs.

California Household Greenhouse Gas Production

Household electricity use is about 6,000 kWh per household per year, for 3 residents average per household.  So the household use per capita is 2,000 kWh or about ¼ of the 8,000 kWh per capita electricity from all applications.  In Laguna Beach the household average is 2.05 residents, however, making the household power usage of 3,000 kWh per capita.  The actual average household use by utility are 6,300 kWh for PG&E, 5,400 kWh for SDG&E, 6,100 kWh for SCE, but only 4,100 kWh for LADWP. The generation of the 6,000 kWh by SC Edison will produce 660 lbs of CO2 per 1000 kWh, as discussed below in Addendum 1.  The 6,000 kWh for a Southern California house hold will then produce 4,000 lbs of CO2 per year.  The main problem in fossil fuel generation of electricity is that both natural gas and coal plants are an average of only 34% efficient in generating electricity.  This is why conservation is always the most effective “energy resource”.  A kilowatt hour saved in conservation is equivalent to burning up 3 kilowatt hours of fossil fuel.


Household Natural Gas use:  400 therms per household x (100,000 BTU/therm) gives 40 million BTU x (117 lbs CO2/million BTU) = 4,700 lbs CO2 per year.  We note that this is about the same CO2 emission as that of the average household electricity use.


            Total average household CO2 generation:

Totaling 4000 lbs CO2 from electricity plus 4700 lbs CO2 from natural gas gives 8700 lbs of CO2 generated per year by an average household.  For comparison, California total greenhouse gas CO2 equivalent in 2001 per capita was 23,000 lbs. Total greenhouse gas emission per capita in the US in 2001 was 48,000 lbs CO2 equivalent.  California’s production of only half the US greenhouse gases is due to good climate, use of natural gas for electricity instead of coal, and hydro, geothermal, wind and solar alternate energy sources. 


Solar Water Heating

Installing solar water heating for somewhere around $4,000-$6,000 is said to save 2/3 of the water heating part of the gas bill.  (The EPA quotes 50% to 80% savings.)  You can get a 30% federal tax credit up to $2,000 until Jan. 1, 2008 on a solar water system. A new California Bill AB 1470 (The Solar Hot Water and Efficiency Act of 2007) also gives a rebate of the order of $1,000 per system.  Its goal is to install 200,000 solar water systems by 2018 with $250 million in rebates.  With an average of 400 therms total natural gas usage, the water heating portion is on average 50% giving 200 therms.  Saving 2/3 of this eliminates 133 therms.  The CO2 generated is then 2/3 of half of the 4700 lbs of CO2 or 1600 lbs of CO2 savings per year. At the rate of $1.20 per therm over baseline, the 133 therms saved results in a $160 savings per year.  Separately or in addition, low flow shower heads, turning down the hot water tank temperature, using economy cycles on the dishwasher and washing machine, and cold water clothes washing will save gas.


Compact Fluorescent Bulbs and Other Electricity Savings

The first thing we can do in the house is to replace all lighting with Compact Fluorescent Bulbs, which take only ¼ of the power for the same light.  Since

lighting is 22% of home electricity, removing ¾ of it saves 17% or 1/6 of the total 6,000 kWh, leaving only 5,000 kWh of household electricity.  At $0.10 per kWh, this gives a yearly savings of $100.  The 1/6 savings of CO2 emissions from electricity is (1/6) x 4000 lbs CO2 or a reduction of 670 lbs of CO2 per year.  This is where more energy efficient appliances and air conditioning come in, as well as solar adaptation by awnings, tinted or upgraded windows and use of fans to lessen the cooling needs of the house.  Getting rid of a second fridge, replacing an old one, turning off equipment when not in use, and avoiding 400 watt plasma screen televisions also help.  The plasma set will use over 600 kWh per year, as will background electricity for electric devices and chargers, even when not in use.

Space Heating

Space heating is about 40% of natural gas usage in the home, producing 1900 lbs CO2 per home in Southern California.  Clearly, bringing down the gas heating needs by thermostat management to not heat when we are gone, and to consider sweaters and comforters to maintain lower temperatures at night will pay off.  It may also be possible to heat only the rooms we are in by shutting the heating vents to the other rooms and closing doors.  Designing houses for solar heating is a longer range solution, and window coating and upgrades are nearer term aids. 

Reduction of Total Household Energy Use

We have shown how to reduce CO2 from household electricity from 4000 lbs to 3300 lbs by using CFL lights. CO2 from natural gas can be reduced from 4700 lbs to 3100 lbs by installing solar water heating.  The average total of 8700 lbs CO2 can then be reduced to 6400 lbs CO2 per year, a reduction of 26%.


Automotive Production of Greenhouse Gases

We must remember that in the State of California, while total electricity generates 22% of greenhouse gases, transportation generates 40%.  This is not all by household drivers of course, and includes air transport and trucking, but still in the service of the people of the household.  Considering a prototypical 25 miles per gallon (mpg) car averaging 15,000 miles a year requires 600 gallons of gas, which in energy at 1.33 therms per gallon gives 800 therms or 80 million BTU. Using 164 pounds of CO2 per million BTU gives 13,000 lbs of CO2 or 6.5 tons for the prototypical commuter per year. This is 36% greater than the entire household energy use. The largest SUVs or light trucks get about 12 mpg on average, and you can double the CO2 production to 13 tons per year.  So the largest SUVs or light trucks use almost as much energy as three households.  Switching a vehicle that gets 25 miles per gallon to one that gets 50 mpg or a future plug-in hybrid that gets the equivalent of 100 mpg can cut in half or a quarter one or more of the 6.5 CO2 tons per year cars. At the current time, SUVs and light trucks are now 53% of all new vehicles sold nationwide.  They are required to have a CAFE standard fleet average of 22.2 mpg compared to cars which have a CAFE standard of 27.5 mpg.  Other alternatives to driving are public transportation, car pooling, biking, walking, combining trips, or avoiding transportation through the use of modern communications. 


Addendum 1:  California’s Average CO2 Production by Major Utilities

California’s Emissions as a State

The greenhouse gas free electricity production does not have to be counted in the electricity account.  We will evaluate coal and natural gas plant CO2 production assuming that they all operate at the average US value of 34% efficiency.  This gives for coal, 2080 lbs of CO2 emission per 1000 kWh, and for natural gas, 1170 lbs of CO2 emission per 1000 kWh.  By 2010, 20% of the State of California’s electricity will be produced by renewable resources (currently 11%) from large scale solar thermal, concentrator solar photovoltaic, wind and geothermal.  Add this to the hydroelectric share of 19% and the nuclear share of 13% will give 52% of electricity which is greenhouse gas (GHG) free.  The per capita electricity is about 8,000 kWh per year. The Governor has also proposed a 33% renewable fraction by 2020.  This would bring us to 65% GHG free electricity, and the remaining 35% of 8,000 kWh would be 2800 kWh, eventually only from natural gas.  At 1170 lbs CO2 per 1000 kWh from natural gas plants, this would give 3300 lbs CO2 per year per capita.  Natural gas plant efficiencies can be increased up to 59% by a combined cycle of gas turbines followed by the standard steam turbines. Most new plants are of this type.  Cogeneration plants that find a use for the heated water, can increase efficiencies up to 85%.  California Bill SB 1368 requires that any plant under new contracts must meet combined-cycle emission limits of 1,100 lbs of CO2 per megawatt hour.

Emissions of CO2 by Major California Utilities

            Lacking explicit data from each utility for its emissions, we evaluate them using their source breakdown, and by assuming 34% efficiencies for their coal and natural gas plants.  This gives for coal, 2080 lbs of CO2 per 1000 kWh; and from natural gas, 1170 lbs CO2 per 1000 kWh.  We compare them by calculating their emissions for 1000 kWh of electricity.

Southern California Edison Emissions

The percentage of greenhouse-gas-free power is different for different power companies in the State.  Hydroelectric power is mostly in the North part of the State.  For SC Edison for 2006, nuclear is 17%, renewables are 16%, large hydro is 5%, coal is 8%, and natural gas is 54%.  The renewable power is mainly geothermal at 9%, followed by wind at 3%, biomass at 2%, and solar and small hydro at 1% each.   So for now 38% of SC Edison electricity is greenhouse-gas-free, and by 2010, when renewables are increased to 20%, 42% of SC Edison’s power will be greenhouse-gas-free.


For 1000 kWh, we have CO2 emissions from natural gas at 54% and coal of 8% giving:

540 kWh  x (1170 lbs CO2 from gas/ 1000 kWh) +  80 kWh x (2080 lbs CO2 from coal/ 1000 kWh) = 632 + 166 = 798 lbs CO2 per 1000 kWh.  From California Air Resources Board (CARB), however we see a greenhouse emission factor for SC Edison of 660 lbs CO2 per 1000 kWh, and our simple estimate is 20% over this.  This could be because they do not include out of state coal sources, and their natural gas generating plants are more efficient than we have assumed.  This disagreement is still under study.

San Diego Gas and Electric Greenhouse-Gas-Free Power     

For SDG&E for 2006, nuclear is 15%, renewables are 8%, large hydro is 10%, coal is 18%, and natural gas is 50%.  The renewable power is mainly wind at 3%, biomass at 3%, and geothermal at 2%.   So for now 33% of SDG&E electricity is greenhouse-gas-free, and by 2010, when renewables are increased to 20%, 45% of SDG&E’s power will be greenhouse-gas-free.


For 1000 kWh, we have CO2 emissions from natural gas at 50% and coal of 18% giving:

500 kWh  x (1170 lbs CO2 from gas/ 1000 kWh) +  180 kWh x (2080 lbs CO2 from coal/ 1000 kWh) = 585 + 374 = 949 lbs CO2 per 1000 kWh.


Comparison to LADWP, SMUD and PG&E Greenhouse-Gas-Free Power

For comparison, Los Angeles Department of Water and Power operates on 48% coal, 30% natural gas, and only 6% hydro, 10% nuclear and 6% renewables, for a present total of 22% greenhouse-gas-free.  We must mention here that coal is twice as CO2 polluting as natural gas for the same energy, further downgrading their greenhouse-gas-free percentage.  As above, this mix generates the comparative maximum of 1349 lbs CO2 per 1000 kWh.


The Sacramento Municipal Utility District (SMUD) takes advantage of hydro power in the North to be 47% hydro, 12% renewable, and 41% natural gas, and using no coal or nuclear (having shut down their nuclear plant by a ballot measure).  So they are the State leader at 59% greenhouse-gas-free, and by 2010 at 20% renewable will be 67% greenhouse-gas-free.  This mix generates 853 lbs CO2 per 1000 kWh.


Pacific Gas and Electric (PG&E) has 19% hydro, 23% nuclear, 13% renewables, 42% natural gas, and only 3% coal.  So it is now 55% greenhouse-gas-free, and by 2010 will be 62% greenhouse-gas-free.  This mix generates the comparative minimum of 553 lbs CO2 per 1000 kWh.


Addendum 2:  California Greenhouse Gas Emissions From 1990-2004

Comparison of US and California Greenhouse Gas Emissions


California greenhouse gas emission per capita in 2001 was about 11 metric tons or 23,000 pounds CO2 equivalent.

US greenhouse gas emission per capita was about 20 metric tons or 48,000 pounds CO2 equivalent.  Due to factors such as good climate, advanced emission standards including only allowing natural gas plants in state, and the availability of hydro, geothermal, wind and solar power, California’s per capita emissions are only half of those of the United States per capita.


California’s Gross Greenhouse Gas Emissions by Source from 1990 to 2004

During the Period 1990 to 2004, California population rose from 30 million to about 36 million, about a 20% increase.


Total Emissions of all greenhouse gases in California, in Million Metric Tons of CO2 Equivalent (MMTCO2), rose from 427 in 1990 to 492 in 2004, an increase of 15% (the rise occurred in the time interval 1996-2001).


            The share that is direct CO2 emissions rose from 317 to 356, for a 12% increase.

            In sectors of direct CO2 sources of emissions:

                        Transportation rose from 161 to 188, an increase of 17%.

                        Total electricity production rose from 80 to 108, an increase of 35%.

Industrial stayed flat from 66 to 67.

Residential decreased slightly from 29 to 28 (this is mainly home natural gas use)

Commercial stayed flat around 12.

Land Use Change and Forestry Sink stayed flat at around -21.


Conclusions:  Most CO2 production sources stayed flat despite a 20% population increase.  But in the largest sources, transportation rose with population, and CO2 production from electricity production increased at double the rate of the population increase.

In terms of a per capita interpretation of the Kyoto agreement, since population had grown by 20% over this period, but greenhouse gas emission had only grown by 15%, California by 2004 had reduced its greenhouse gas generation per capita by 5%, almost meeting the Kyoto goal of a 7% reduction, had the population stayed constant.  For cities that have not grown, they may already be near the Kyoto goal.