A mandatory time-of-listing HES policy requires that homebuyers be provided reliable information about home energy performance before the time of purchase to inform decision making. The policy aims to encourage investments in improvements that lower utility bills, reduce carbon emissions, and increase the comfort, safety, and health of the household. Mandatory programs make home energy information widely available, and are typically less expensive to administer than voluntary programs.

The policy encourages energy efficiency upgrades, especially for older homes, which will result in reduced energy consumption and expenses over time. A 2024 analysis in the City of Portland found that homes with an HES were 10 times more likely to receive an energy efficiency upgrade than homes without an HES. An analysis for Thurston County estimated that the policy would result in a range of 243 to 649 annual home retrofits, resulting in up to $360,000 in total energy cost savings and 670 tons of CO2 emissions reduced per year.

HES assessments are done by private-sector professionals who obtain an HES certification through U.S. Dept. of Energy. 

They will not be conducted by the Thurston County Assessor’s Office or other government employees. 

To learn more about the certification, visit: https://betterbuildingssolutioncenter.energy.gov/home-energy-score/become-assessor

It is estimated that 6 to 8 full-time HES assessors will be needed to meet the demand for energy scores in Thurston County. Other regions have seen a significant increase in the number of local certified energy assessors following the adoption of a new HES disclosure policy. 

The ordinance allows for a year of workforce development and education before the requirement takes effect. 

The ordinance applies to buildings that are covered by the HES rating tool: detached single-dwelling units and attached dwelling units that extend from foundation to roof (e.g., duplex, rowhouse, or townhome). The tool is not suitable for homes in a stacked configuration with other units above or below. It is also not suitable for mobile, manufactured, or floating homes.

No. A large number of rental units in Thurston County are stacked multifamily apartments, which currently cannot be scored in the Home Energy Score model.

No, the ordinance only applies to residential properties.

Before the first sale of a newly constructed subject building, the ordinance allows the seller to either:
A. Provide a HES that was generated from either design specifications or an on-site inspection. 
B. Obtain and replicate a single HES for subject buildings constructed within the same land division using identical design specifications with identical features.
 

The ordinance includes exemptions for: 
•    Subject buildings on federal land or tribal land 
•    Transfer of real property as defined by RCW 64.06.010 (foreclosures, gifts, transfers in connection with marital dissolution, transfers by trustees, etc.) 
•    Cases of undue hardship for the seller

Qualifying low-income households may either be exempt or may receive subsidized Home Energy Score assessments, depending on available funding.  
 

The average cost of an HES assessment is $150 - $350. 

The County will either subsize the HES for qualifying low-income homeowners, or exempt them from the requirements.

The HES score is valid for ten (10) years after the assessment date, provided no changes in the home to the following: 

• Mechanical systems
• Building envelope
• Energy efficiency
• Square footage

The HES is the most commonly used rating system in local government energy assessment and disclosure policies, can be easily applied to existing homes, and has a lower cost than other assessment tools (like the Home Energy Rating System; HERS). 

The HES is an “asset rating” which means it calculates energy efficiency based on the home’s physical assets (size, envelope, and heating/cooling equipment). This approach provides objective energy efficiency information that is independent of occupant behavior. An asset score allows prospective buyers and homeowners to compare the energy performance of multiple homes based on their assets, rather than how they are operated by current occupants.

Operational data (a home’s past utility bills) is often simple to provide and may be more familiar to consumers, but it is heavily dependent on occupant behavior and therefore a poor predictor of future energy costs. Operational data also does not include recommendations for cost-effective energy improvements.

The proposed policy requires energy information to be disclosed at the earliest possible stage in the real estate transaction process (time of listing), which makes the information more actionable for prospective buyers and the market. Early disclosure allows buyers to compare the energy performance, expected energy costs, and recommended efficiency upgrades for all prospective homes. It also may enable buyers to finance recommended energy improvements as a part of their home mortgage, or to qualify for a lower-rate “EnergySpark” home loan.

The home inspection takes place after the purchase offer is accepted. If the HES were done at that time, it would be too late in the real estate transaction to allow prospective buyers to compare homes or to include energy improvements in mortgage products. This type of time-of-sale disclosure may also complicate or delay the real estate closing.
 

An HES program in Thurston County is expected to cost $80,000-$100,000 to develop and launch (one-time cost), then about $25,000 annually to implement it. These costs will be shared among all jurisdictions that adopt the ordinance. Thurston County, Olympia, Lacey, and Tumwater are all considering the ordinance for adoption.  

No. Thurston County and the cities would not require homeowners to make improvements to their home without a program to mitigate the financial impacts on low-income homeowners. The jurisdictions do not currently have the funding to subsidize the cost of energy efficiency improvements on a recurring basis.

Older homes may receive lower scores due to lower efficiency standards at the time of construction. However, observed impacts on sale prices are modest. Communities with HES disclosure requirements have found that a one-point increase in the HES is associated with an average 0.5% increase in sale price (approximately $2,500 on a $500,000 home), while a $100 increase in estimated annual energy costs is associated with a 0.4% decrease in sale price (about $2,000 on a $500,000 home).

Source: https://www.aceee.org/white-paper/2025/07/energy-ratings-home-sales.

Other jurisdictions with an HES policy in place, such as Bend, OR and Portland, OR, report that residents can get assessments scheduled within a few days, and receive the score a few days after that.