U. C. Irvine
Physics and Astronomy
October 2007
Introduction
We show that in SouthernCalifornia, the three household energy domains of electricity, hot waterheating, and space heating use about equal energy. We provide a simplestrategy to reduce greenhouse gases from electricity and hot water heating to athird of their present values at modest cost. Space heating will requiremore detailed attention from homeowners.
Data Source:
The California Statewide Residential Appliance Saturation Study,2004. Numbers have been rounded offto make the relative magnitudes easier to perceive, and any errors in thecalculations are my own.
Total Electricity usage (all applications) per year for comparison:
USA 12,000 kWh per capita
California 8,000 kWh per capita
Average of SC Edison and San Diego Gas and Electric
Household electricity use: 6,000kWh per household per year for 3 residents averageper household. So the household use per capita is 2,000 kWh or about ¼ ofper capita electricity from all applications.
Household Natural Gas use:400 therms per household x 30 give 12,000 kWhequivalent electricity. Since much of the electricity is generatedby natural gas, it is not totally unreasonable to compare these two in kilowatthours. We note that heating water and households by natural gas usestwice the power of household electricity.
Total average household power usage:
6,000 kWh electricity plus 12,000 kWh gas equivalent = 18,000 kWhper year.
Proposed standards for low energy usage per year
The average household area for the above data is 1500 square feet.
A standard being considered by
0.23 x 1500 x 12= 4140 kWh per year. This is supposed to include the gasusage as well.
A shorter term goal to comply withthe Mayor’s Program would be a 20% reduction, bringing the total down to 16,000kWh per year.
An alternative standard is areduction to a sustainable production of carbon dioxide which is only 20% ofthe current rate. If that is applied separately to the household total of18,000 kWh per year it would give a goal of 3,600 kWh which is less than the“international” standard. A goal of 80% GHG generation below 1990levels by 2050 has been set forward in Executive Order S-3-05 by GovernorSchwarzenegger, and could be about the same as the above since per capitaelectricity has been stabilized in California.
Comparison: Thus the current average usage is 5 times the Governor’s2050 goal.
Solar Water Heating
Installing solar water heating for somewherearound $3,000-$7,000 is said to save 2/3 of the water heating section of thegas bill. (The EPA quotes 50% to 80% savings.) (You can get a 30%tax credit up to $2,000 until Jan. 1, 2008 on a solar water system.) With anaverage of 400 therms total gas usage, the water heating portion average is onaverage 50% at 200 therms. Saving 2/3 of this cuts out 200*(2/3)*30=4000kWh. This cuts the 12,000 kWh down to 8,000 kWh equivalent forgas. At the rate of $1.20 per therm over baseline, the 200 therms savedresults in a $240 savings per year. Separately or in addition, low flowshower heads, turning down the hot water tank temperature, using economy cycleson the dishwasher and washing machine, and cold water clothes washing will savegas.
Compact Fluorescent Bulbs and Other Electricity Savings
The first thing we can do in thehouse is to replace all lighting with Compact Fluorescent Bulbs, which takeonly ¼ of the power for the same light. Since
lightingis 22% of home electricity, removing ¾ of it saves 17% or 1/6 of the total6,000 kWh, leaving only 5,000 kWh of household electricity. At$0.10 per kWh, this gives a yearly savings of $100. This is where moreenergy efficient appliances and air conditioning come in, as well as solaradaptation by awnings, tinted or upgraded windows and use of fans to lessen thecooling needs of the house. Getting rid of a second fridge, replacing anold one, turning off equipment when not in use, and avoiding 400 watt plasmascreen televisions also help.
California’s Greenhouse-Gas-Free Power
The greenhousegas free electricity production does not have to be counted in the electricityaccount. By 2010 or at the latest 2017, 20% of the Stateof California’s electricity will be produced by renewable resources(currently 11%) from large scale solar thermal, concentrator solarphotovoltaic, wind and geothermal. Add this to the hydroelectric share of19% and the nuclear share of 13% will give 52% of electricity which isgreenhouse gas (GHG) free. The remaining 48% of the 5,000 kWh RenewableElectricity Production h electricity gives 2,400 kWh GHG pollutingelectricity per household (currently 16% coal and 42% natural gas). Inthis we are assuming that the almost double (1.78) CO2 polluting coalproduction of electricity from out of state sources is replaced by therenewable resources. (This will certainly occur by 2027 when the Coalcontracts of Los Angeles and Anaheim run out.) The Governor has alsoproposed a 33% renewable fraction by 2020. This would bring us to 65%renewable electricity, and the remaining 35% of 5,000 kWh would be 1,800 kWhGHG polluting. This would reduce us to only generating greenhouse gasesfrom 30% of the initial electricity we used.
Southern California Edison Greenhouse-Gas-Free Power
The percentageof greenhouse-gas-free power is different for different power companies in theState. Hydroelectric power is mostly inthe North part of the State. For SCEdison for 2006, nuclear is 17%, renewables are 16%, large hydro is 5%, coal is8%, and natural gas is 54%. Therenewable power is mainly geothermal at 9%, followed by wind at 3%, biomass at2%, and solar and small hydro at 1% each.So for now 38% of SC Edison electricity is greenhouse-gas-free, and by2010, when renewables are increased to 20%, 42% of SC Edison’s power will begreenhouse-gas-free.
San Diego
For SDG&Efor 2006, nuclear is 15%, renewables are 8%, large hydro is 10%, coal is 18%,and natural gas is 50%. The renewablepower 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&Es’power will be greenhouse-gas-free.
Comparison to LADWP, SMUD and PG&E Greenhouse-Gas-Free Power
For comparison, Los AngelesDepartment of Water and Power operates on 48% coal, 30% natural gas, and only6% hydro, 10% nuclear and 6% renewables, for a present total of 22%greenhouse-gas-free. We must mentionhere that coal is twice as CO2 polluting as natural gas for the same energy,further downgrading their greenhouse-gas-free percentage.
The Sacramento Municipal UtilityDistrict (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 shutdown their nuclear plant by a ballot measure).So they are the State leader at 59% greenhouse-gas-free, and by 2010 at20% renewable will be 67% greenhouse-gas-free.
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.
Space Heating
Space heating is about 40% ofnatural gas usage or 4800 kWh equivalent in the home in SouthernCalifornia. Clearly bringing down the gas heating needs by thermostatmanagement to not heat when we are gone, and to consider sweaters and comfortersto maintain lower temperatures at night will pay off. It may also bepossible to heat only the rooms we are in by shutting the heating vents to theother rooms and closing doors. Designing houses for solar heating is alonger range solution, and window coating and upgrades are nearer termaids.
Reduction of Total Household Energy Use
We are now down to about 8,000 kWhfrom gas and 1,800 kWh from electricity for a total of 9,800 kWh total ofGHG producing household usage, down from the initial 18,000 kWh. Thisbrings us down to 2.4 times the proposed standard.
But what about the 5,000 pound Gorillas sitting outsidethe house?
We must remember that while totalelectricity generates 22% of greenhouse gases, transportation generates40%. Thus in terms of the 8,000 kWh per capita for total electricity,transportation generates the equivalent of 14,500 kWh per capita. Now thehousehold of three has an equivalent of 44,000 kWh per household intransportation. This is not all by household drivers of course, andincludes air transport and trucking, but still in the service of the people ofthe household. Taking a prototypical 25 miles per gallon (mpg) caraverage at 15,000 miles a year requires 600 gallons of gas, which in energy isequivalent to 23,400 kWh, although it will generate more equivalent natural gasgreenhouse gases by a ratio of 1.40, leading to an equivalent GHG generation ofnatural gas of 33,000 kWh. That is almost double the entire household energyuse. The largest SUVs or light trucks get about 12 mpg average, and you candouble this figure. So those use as much energy as four households.Switching a vehicle that gets 25 miles per gallon to one that gets 50 mpg or afuture plug-in hybrid that gets the equivalent of 100 mpg can cut in half or aquarter one or more of the 33,000 kWh equivalent cars. Other alternativesare public transportation, car pooling, biking, walking, combining trips, oravoiding transportation through the use of modern communications.
California Greenhouse Gas Emissions From 1990-2004
Total Emissions in MillionMetric Tons of CO2 Equivalent (MMTCO2) rose from 427 in 1990 to 492 in2004, an increase of 15% (the rise occurred between 1996-2001).
The direct CO2 emissions rose from 317 to 356, for a 12% increase.
California population rose from30 million to about 36 million, about a 20% 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%.
Industrialstayed flat from 66 to 67.
Residential decreased slightlyfrom 29 to 28 (this is mainly home natural gas use)
Commercialstayed flat around 12.
Land Use Changeand Forestry Sink stayed flat at around -21.
Conclusions: Most CO2production sources stayed flat despite a 20% population increase. But inthe largest sources, transportation rose with population, and CO2 productionfrom electricity production increased at double the rate of the populationincrease.
