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On the Path toward Zero Carbon Homes: The Comparative San Diego Case Study. Barbara C. Farhar, Ph.D. National Renewable Energy Laboratory (Ret.) Senior Research Fellow, IBS Presentation for Center for Science and Technology Policy Research University of Colorado at Boulder

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on the path toward zero carbon homes the comparative san diego case study

On the Path towardZero Carbon Homes: TheComparative San Diego Case Study

Barbara C. Farhar, Ph.D.

National Renewable Energy Laboratory (Ret.)

Senior Research Fellow, IBS

Presentation for Center for Science and

Technology Policy Research

University of Colorado at Boulder

October 20, 2008

outline of presentation on study highlights
Outline of Presentation on Study Highlights
  • Study background and methods
  • Home sales prices/builder incentives
  • Uptake of optional PV systems
  • Who are the homebuyers?
  • Resale value
  • Purchase decision and satisfaction
  • Utility data analysis
  • Toward zero-carbon buildings
photo of shea homes development
Photo of Shea Homes Development

SheaHomes at Scripps Highlands

sheahomes home
SheaHomes Home

SheaHomes Home

the anatomy of high performance by sheahomes
The Anatomy of High Performance by SheaHomes

The Anatomy of High Performance by SheaHomes

comparison home
Comparison Home

Comparison Home

preliminary work
Preliminary Work
  • Project advisory group
  • Numerous interviews of SheaHomes executives/staff, organizations partnering with the builder, and other interested parties
  • Qualitative face-to-face interviews with 43 respondents in 25 SheaHomes households on reasons for purchase and perception of their energy features

Period of study: 2001 - 2006

other qualitative data
Other Qualitative Data
  • Background information/observation home sales processes
  • Focused interviews with lookers for new homes
  • Other artifacts, such as TV coverage, print news clips, press releases
  • Interviews with utility staff on grid-tied PV, net metering, dates of meter reading of study households, and other points
sheahomes and comparison homeowners surveys
SheaHomes and Comparison Homeowners Surveys
  • Based on earlier qualitative analysis
  • Universe of study: 306 SheaHomes, 103 comparison homes (63% response rate)
  • Four overlapping mail questionnaires

Other Quantitative Data

  • Home sales and characteristics (SheaHomes data)
  • Public records on sales
  • Utility data for 132 SheaHomes and comparison homes (who gave permission) collected on
  • Therm and kWh usage and costs
  • Monthly combined utility costs
home sales prices
Home Sales Prices
  • High-performance homes are competitive on the market
  • Based on actual sales data, per square foot, they sold for 9.2% less than comparison homes, on average
sales prices controlling for presence of pv system mean price sq ft
Sales Prices Controlling for Presence of PV System(Mean Price/sq.ft.)
  • PV - $198.45
  • Non-PV - $194.36
  • Comparison - $215.89
  • p=.000
optional pv system prices
Optional PV System Prices
  • 1.2 kW system: $6,000 (later, $7,000)
  • 1.2 kW upgrade: $4,000
  • 2.4 kW system: $10,000 (later, $11,000)
builder incentives and net costs
Builder Incentives and Net Costs
  • Incentives to builder: $750 solar water heating rebate from CEC (SB 1345) (~44%)
  • 50% subsidy PV system cost from CEC (first time to California builder)
  • 15% state tax credit on system cost
  • Net cost of providing each 1.2 kW PV system standard was $3,380
  • Estimated net cost of offering the swh and PV was $512,910, or $1,751 per house (n=293 in total; 120 of them PV homes)
  • SheaHomes: “We didn’t lose money.”
other benefits to sheahomes
Other Benefits to SheaHomes
  • Homes sold out a year faster than expected
  • Partnerships with new organizations
  • Extensive media coverage worth $1 mn in advertising in less than a year
  • Enhanced reputation and community goodwill
  • Favorable relationship with the City
other costs to sheahomes
Other Costs to SheaHomes
  • Learning curve
  • Selling and scheduling optional PV systems
  • Obtaining the rebates
  • Interconnectivity issues
  • Other issues
uptake of optional pv systems
Uptake of Optional PV Systems
  • All SheaHomes highly efficient, came with solar water heating standard
  • 120 of 306 SheaHomes had PV
  • Most PV systems came standard
  • Only 260 homes were PV-eligible
  • Only 12% of all PV-eligible homes were sold with PV optionally
  • However, 56% of those who could have purchased optional PV systems were not told about the option
  • Of those actually offered PV systems, the uptake rate was 44%

SheaHomes Buyer Quotes

  • “It’s best to integrate the solar electric system into the entire home purchase rather than having it offered as an option in a piecemeal way. It should all be rolled into the overall price.”
  • “We wanted to get the house because the system was already there. We didn’t have to decide about it. We’re glad it’s here. We’re lucky to have the PV.”
  • “We feel the builders know what they are doing, so if they offer the solar as part of the package, there must be a reason.”
who were these homebuyers
Who Were These Homebuyers?
  • Buyers of high performance homes and buyers of new conventional homes shared the same demographic characteristics, environmental attitudes, and early adopter chacteristics
  • As expected, buyers mostly represented upper-middle class married couples with children, or mature couples
  • They were relatively affluent with well paying occupations

Respondent Household Demographics

No demographic differences between SheaHomes and comparison homes, except income

Gender: Male -- 56%; female -- 44%

Age: 44% up to 39; 30% between 40 to 49; 26% were 50 years of age or older

Marital status: 95% married

Households: 68% -- two adults with children; 32%-- two adults


Respondent Household Demographics (cont’d.)

Mean household size: 3.53 occupants (range: 1-11)

Highly educated: 80% at least Bachelor’s degrees; 20% Master’s degrees,

16% with doctorates

Reported occupations: business owners, financial managers, scientists and engineers, doctors and lawyers


Respondent Household Demographics (concluded)

76%of comparison owners report annual household incomes of $200K or more compared with 59% of SheaHomes; 19% of SheaHomes report $200K annual incomes compared with 4% of comparison (p=.048)

One-third plan to stay permanently; 44% didn’t know how long they’d stay

86% moved from the San Diego area

  • Concern about aesthetics could not be discerned in this study
  • Resale prices quite high
  • Homeowner quotes on aesthetics of solar panels
    • “Huh?”
    • “Satellite dishes are more offensive”

Original and Resale Prices(as of 2/7/05)





















home purchase decision process
Home Purchase Decision Process
  • 75% of each category of buyers visited the other development
  • Neither category knew much about energy features when they were shopping
  • The 2001 San Diego electricity crisis did not drive home purchase decisions
  • Most of the comparison buyers were unaware of SheaHomes’ energy-efficiency and solar energy features

Homebuyer Satisfaction

“We would buy our same house again

if we had it to do over.”

(Chi-square test; p=.048)

homeowners differ
Homeowners Differ….
  • On variables affected by their experiences in living in their new homes
  • Especially, the experience of PV ownership changes attitudes, perceptions, and behavior
pv owners
PV Owners
  • Report the lowest monthly utility bills
  • Tend to think electricity rates fell
  • Had a more positive attitude toward SDG&E
  • Used their digital displays for feedback and watched their meters run backwards for “kicks”
  • Changed to some degree their energy behavior because of feedback
  • Report they know more about ee/re
  • Seem more sensitive to savings from solar water heating systems
sheahomes vs comparison homes electricity billing data

Home Category

Avg. Monthly


% Savings

Comparison homes



SheaHomes energy efficiency/ solar water pre-heating (HPH homes)



Shea HPH + 1.2 kW PV



Shea HPH + 2.4 kW PV



SheaHomes vs. Comparison Homes (Electricity Billing Data)
grupe green homes carsten crossing july 2007
Grupe Green HomesCarsten Crossing, July 2007
  • Sold 4.6 near-ZEHs/mo. compared with 1.9 per mo. by 8 other builders
  • Carrying cost $311,000/mo
  • Sold 144 in 31 mos., saving $14 mn. In carrying costs
  • If just 18.8% of accelerate pace of sales due to green features, the program paid for itself.
sheahomes at trilogy green boomer housing
SheaHomes at TrilogyGreen Boomer Housing
  • “Trilogy by SheaHomes sets new green home building standards across the U.S.”
  • “Nation’s largest privately held home builder creates Shea Certified Green Program to reduce carbon footprint in its Boomer Resort Community Homes by as much as 29% in 2008.”
next west home zero carbon home
Next West HomeZero-Carbon Home
  • See photo
  • 426 Spruce, Boulder
  • Bruce Oreck funding
  • Jim Logan, architect
  • Bob Hughes, builder
  • 3,500 sq.ft., 10 kW PV, geothermal heating, ee appliances, advanced insulation, off-the-shelf technologies
next west home
Next West Home
  • Bruce Oreck, owner; Jim Logan, architect
  • Builders should offer ZEHs standard (not optional) (high efficiency, solar thermal, larger PV systems)(other models possible)
  • Include digital displays that conveniently show kWh production and consumption
  • Seek turnkey packages
  • Early adopters relative to ZEHs are builders, utility companies, and ZEH policy makers (not homebuyers)
  • ZEH homebuyers are not a niche market; they are THE market
some policy implications
Some Policy Implications
  • Pass net metering legislation (states)
  • Foster incentives for ZEHs (states, federal)
  • Certify, label ZEHs (EPA)
  • Implement legislation for RPS, solar setasides (states, possibly federal)
  • Phase in ZEH mandates for all new housing (states)
  • Develop ZEH mortgage financing (Fannie Mae, Freddie Mac, HUD)
  • Redevelop disaster areas (FEMA), low-income housing (HUD), and military housing (DOD) with ZEHs
  • Increase support ZEH R&D (DOE)
zehs as best building practice
ZEHs as BestBuilding Practice
  • 10/18/07 CPUC decision 7-10-032
  • Affirmed cost-effective energy-efficiency measures highest energy priority
  • All new residential construction in California to be net-zero energy by 2020
  • All new commercial construction net zero-energy by 2030
boulder policies
Boulder Policies
  • Net zero-energy homes – new homes in Boulder County 5000 sq. ft. starting May 1, 2009
  • Boulder County Ordinance 1A – front-end cost of energy efficiency and renewable energy installations – new or retrofit – funded through bonds to provide low-interest loans repaid through property tax assessment. If it passes
  • Xcel Energy Smart Grid City - Boulder
  • Report at www.nrel.gov Publications data base Author search: Farhar 1st publication listed (2 vols.)
  • Email: [email protected]
  • Phone: 303-492-5452
  • Web site: www.barbarafarhar.com
  • Thank You!