Select a Topic Below
Property Values (Solar) |
Electromagnetic Field Impact |
Property Values (Solar)
Property value is dependent on many factors, including the size and amenities of the affected property, improvements made to the property, and the attributes of the surrounding neighborhood. Previous research has suggested that distance to “environmental disamenities” is a contributing factor in adversely affecting property value, although property value declines have been more consistently observed in residential properties that are near higher-risk disamenities (e.g., hazardous waste facilities) or facilities that lack adequate land or vegetation buffers.
Virtually all credible research into property value impacts has derived its conclusions from appraisal studies or econometric techniques. Most appraisal studies use a comparable sales approach, which is largely dependent on the appraiser’s expert judgment in locating and refining a set of comparable sales for analytical purposes. Although appraiser studies often use records of sales prices or assessments from a large number of properties, the analysis is usually confined to descriptive statistics from which only limited inferences can be made. Econometric models attempt to statistically account for factors that influence property values, such as lot size, structural attributes, neighborhood amenities, etc. Econometric studies are data-intensive and often combine data from several distinct sources such as tax rolls, real estate sales records, and survey data.
As the economy transitions to clean, renewable energy, utility-scale solar projects are becoming a common feature of the landscape, and although ground-mounted solar facilities can occupy significant acreage, solar panels, racking, and associated components have a vertical profile that rarely exceeds 12 feet. Still, concerns about alterations to views and other externalities lead to questions about changes to property values and reduced demand for residential properties near solar energy facilities.
While research in this area is nascent, evidence has not revealed significant adverse effects of proximity to a solar installation on residential property values if the solar installation is not visible. This finding has generally relied upon appraisal studies, some commissioned by project developers or affected property owners, using paired sales analysis, that compare sale prices of properties adjacent to a solar facility (adjoining properties) to prices of similar properties in the same real estate market (control properties), or by looking at prices of properties sold prior to and after project development (repeat sales analysis).
Examples include a past siting case in North Carolina for a 21-acre solar facility on a 38-acre parcel in an Agricultural-Residential district, which concluded that utility-scale PV energy systems that are not visible from surrounding properties would have no impact on their market values (Franklin County 2014), and a paired comparison of market values of residential and agricultural properties near operating solar facilities in North Carolina for a proposed 48-acre project outside of Greensboro, NC that came to a similar conclusion (Kirkland Appraisals 2014). While findings from the Franklin County study were based on expert opinion drawn from market valuations of a limited sample of properties near other types of industrial disamenities, the Kirkland study compared adjoining to non- adjoining residential sales prices at three comparable solar facilities in the state, as well as a survey of builders, developers, and investors to conclude the project would have no impact in home values due to the adjacency as well as no impact to adjacent vacant residential or agricultural land.
Of the more recently-published literature, most research has not found a significant relationship between proximity to utility-scale solar facilities on nearby residential property values. This includes evidence gathered from a widely circulated independent survey of home appraisers from multiple states, including Maryland (Al-Hamoodah et al. 2018), a study of utility-scale PV solar installations abutting residential land parcels in the seven-county Twin Cities Metro Area (Marin 2019), and a paired sales analysis of properties adjacent to operating solar projects in Indiana (CohnReznick 2018).
In contrast to these examples, one recent study using a hedonic price model on over 400,000 sales transactions within three miles of solar facilities in Massachusetts and Rhode Island estimated a 1.7% price decline of properties within one mile of operating solar facilities relative to those further away and substantially larger negative effects (a 7% price decline) for properties within 0.1 miles and properties surrounding solar sites built on farm and forest lands in non- rural areas (Gaur & Lang 2020). Comparability to studies cited above is unclear due to the geographic scope of potential effect (3 miles), range of generating capacity (1MW and above), nonrecognition of visual encumbrances, and absence of a disamenity distance variable.
Another recent study examined over 1,500 large-scale PV projects (LSPVPs) and 1.8 million home transactions across six U.S. states that account for over 50% of the installed MW capacity of large-scale solar in the U.S. to determine what effect LSPVPs have on home prices and whether the effect changes based on a number of factors, including prior land use, LSPVP size, and the home’s urbanicity. The study found that homes within 0.5 mi of an LSPVP experience an average home price reduction of 1.5% compared to homes 2–4 miles away. However, these effects were only measurable in certain states, for LSPVPs constructed on agricultural land, for larger LSPVPs, and for rural homes (Elmallah et al. 2023).
Reconciling all these findings in the literature to individual projects is difficult at best since site conditions, project specifications, and the environment in which the project is located is unique. However, project visibility is commonly suggested to be an important mitigating factor in the valuation of properties near solar facilities.
Return to Top
Electromagnetic Field Impacts
Electric and magnetic fields, referred to collectively as electromagnetic fields (EMF), are naturally occurring and result from the generation, transmission, and use of electric power. These fields are present around such things as appliances, electronics, electric wiring, and power lines.
For electric fields, the strength of a field is dependent on the voltage level and the amount of current flow. For example, the amount of current flowing through a power line varies as the demand for electric power changes. Electric fields, measured in units of volts per meter (V/m), are produced by voltage and increase in strength as the voltage increases. Magnetic fields, measured in units of gauss (G) or tesla (T), result from the flow of current through wires or electrical devices and increase in strength as the current increases. Electric fields and magnetic fields are characterized by wavelength, frequency, and amplitude. The frequency of the field, measured in hertz (Hz), describes the number of cycles that occur in one second. Electricity in North America alternates through 60 cycles per second or 60 Hz.
Human Health Considerations
Electric fields are shielded or weakened by materials that conduct electricity (i.e., trees, buildings, and human skin), while magnetic fields pass through most materials and are more difficult to shield. Both electric and magnetic fields decrease rapidly as the distance from the source increases. However, since magnetic fields are not easily shielded, most research in recent years has focused on the potential health effects of magnetic field exposure. Estimated average background levels of 60 Hz magnetic fields in most homes, away from appliances and electrical panels, range from 0.5 to 5.0 milligauss (NIEHS 2002). The Table below shows typical magnetic field levels for common household appliances.
Typical Magnetic Field Levels for Common Household Appliances
|Source||Field Strength at 12 inches (milligauss)||Field Strength at 3 feet (milligauss)|
|Coffee maker||0.09 to 7.3||0 to 0.61|
|Copy machine ||0.05 to 18.38||0 to 2.39|
|Television ||1.8 to 12.99||0.07 to 1.11|
|Vacuum cleaner||7.06 to 22.62||0.51 to 1.28|
|Microwave oven||0.59 to 54.33||0.11 to 4.66|
|Computer monitor||0.2 to 134.7||0.01 to 9.37|
Source: California Department of Health Services
The potential health effects of exposure to EMF in the extremely low frequency (ELF) range from power transmission facilities have been the subject of scientific and public scrutiny for almost 30 years. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) in its 2010 Guidelines concluded that neither a causal relationship between ELF-EMF and increased risk of cancer nor other long-term effects can be established (ICNIRP 2010). Research and assessments done by international expert panels from 2009 to 2018 have reached similar conclusions (Scientific Council on Electromagnetic Fields 2018; SCENIHR 2015).
EMF and Solar Facilities
Photovoltaic (PV) solar panel arrays convert solar energy into Direct Current (DC) electricity. A solar inverter, a component of a PV system, converts the DC output of a solar panel into Alternating Current (AC) that can be fed to the electrical grid. AC electricity produces “power frequency magnetic fields” and DC electricity produces “static magnetic fields.”
Humans are constantly exposed to EMF throughout daily life. While there is no demonstrated causality between long-term (chronic) exposure and adverse health impacts, short-term (acute) EMF exposure may cause negative health effects if the field strength exceeds certain health-based thresholds. The most rigorous exposure guidelines for EMF are those developed by the ICNIRP. For the general public, the ICNIRP has established a threshold for acute exposure of 2,000 milligauss for power frequency magnetic fields (ICNIRP 2010) and 4 million milligauss for static magnetic fields (ICNIRP 2010).
Solar energy systems produce magnetic fields significantly below the minimum thresholds established by the ICNIRP. Solar energy systems will produce power frequency magnetic fields from their AC inverters and grid interconnection, while the DC electricity generated by the PV modules will produce static magnetic fields. A typical solar PV inverter may produce a power frequency magnetic field of about 3 milligauss at a distance of 10 feet; this level is comparable to the levels produced by common household appliances at a distance of only 3 feet.
The United States Department of Energy directed the National Renewable Energy Laboratory (NREL) to conduct a study on the emission of EMFs by solar panels (DOE 2009). NREL found that the magnitude of EMF measured at the perimeter of solar photovoltaic installations has been shown to be indistinguishable from background EMF, and is lower than that from many household appliances such as televisions and refrigerators.
The Table below provides an example of calculated EMF levels for a typical solar PV energy system, specifically the West Linn Highway Solar Project in Oregon. This project evaluation, published by the Oregon Department of Transportation, found that the calculated static field strength at 10 feet from the PV modules was 509 milligauss, well below the ICNIRP static field exposure guideline of 4 million milligauss, and the field strength of the DC to AC power inverters of 3 milligauss (at 10 feet) is well below the recommended exposure limit of 2,000 milligauss for time-varying or power frequency magnetic fields.
EMF Levels at the Proposed 3 MW West Linn Highway Solar Project, Oregon
|Source||Field Type||Field Strength at 3 feet (milligauss)||Field Strength at 10 feet (milligauss)||Corresponding ICNIRP exposure limit for the general public (milligauss)|
|Parallel string of PV modules||Static||1,697||509||4,000,000|
|DC to AC power inverters ||Power frequency||344||3||2,000 (see note)|
|Grid interconnection||Power frequency||14||N/A||2,000 (see note)|
Source: Scaling Public Concerns of Electromagnetic Fields Produced by Solar Photovoltaic Arrays
Note: ICNIRP (2010), Table 4 provides EMF exposure guidelines for the general public. For magnetic fields associated with electric current between 25 Hz and 400 Hz, the recommended limit is 200 microteslas or 2,000 milligauss.
According to a 2020 evaluation conducted for a proposed 120 Megawatt (MW) solar project in Connecticut, the static and power frequency magnetic fields created by solar panels, inverters, and switchgear located within the Project site would have no impact on EMF levels experienced at nearby receptors located 150 feet from the property boundary (Exponent 2020). In that case, the only potential increases in EMF would result from overhead 115 kV transmission lines and underground collector lines extending between different portions of the 485-acre site.
The Federal Aviation Administration (FAA) has indicated that electromagnetic interference (EMI) from solar PV facilities is low-risk. Solar panels do not emit EMI, and the associated equipment operates at a low frequency. According to the U.S. Navy’s Renewable Energy Program Office and NREL, EMI and/or radio interference from solar facilities, at sufficient distance, does not pose a significant concern. Inverters should be sited at least 150 feet away from any navigational and communications equipment, and no part of the PV array should be located within 250 feet of an airfield’s navigation system
Return to Top
Definition of Noise
Noise generally consists of many frequency constituents of varying loudness. Three decibels (dB) is approximately the smallest change in sound intensity that can be detected by the human ear. A tenfold increase in the intensity of sound is expressed by an additional 10 units on the dB scale, a 100-fold increase by an additional 20 dB. Because the sensitivity of the human ear varies according to the frequency of sound, a weighted noise scale is used to determine the impacts of noise on humans. This A-weighted decibel (dBA) scale weights the various components of noise based on the response of the human ear. For example, the ear perceives middle frequencies better than low or very high frequencies; therefore, noise composed predominantly of the middle frequencies is assigned a higher loudness value on the dBA scale. Subjectively, a tenfold increase in sound intensity (10 dB increase) is perceived as an approximate doubling of sound. Typical A-weighted sound levels for various noise sources are shown in the Table below.
Typical Sound Levels for Common Sources (dBA)
|Noise Source||Typical Sound Pressure Level|
|Lowest sound audible to human ear||10|
|Soft whisper in a quiet library||30-40|
|Light traffic, refrigerator motor, gentle breeze||50|
|Air conditioner at 6 meters, conversation||60|
|Busy traffic, noisy restaurant, freight train moving 30 mph at 30 meters||70|
|Subway, heavy city traffic, factory noise||80|
|Truck traffic, boiler room, lawnmower||90|
|Chain saw, pneumatic drill||100|
|Rock concert in front of speakers, sand blasting, thunder clap||120|
|Gunshot, jet plane||140|
Sound energy dissipates with increasing distance from the noise source. For every doubling of the distance, the sound pressure level produced by a given noise source decreases by approximately 6 dBA.
Summary of Regulatory Requirements
Maryland noise regulations specify maximum allowable noise levels, shown in the Table below (COMAR 26.02.03). The maximum allowable noise levels specified in the regulations vary with zoning designation and time of day. The noise limit for residential areas is 55 dBA during nighttime hours and 65 dBA during daytime hours. A noise source may not create noise that exceeds the allowable levels, as measured at the receiving property.
Typical Sound Levels for Common Sources (dBA)
Source: COMAR 26.02.03
Note: Day refers to the hours between 7 AM and 10 PM; night refers to the hours between 10 PM and 7 AM.
The State regulations exempt certain noise sources and noise-generating activities. For example, motor vehicles on public roads are exempt from Maryland noise regulations; however, while on industrial property, trucks are considered part of the industrial source and are regulated as such. The regulations also allow for construction activity to generate noise levels up to 90 dBA during daytime hours, but the nighttime standard may not be exceeded during construction.
While the State has established target levels for noise, enforcement authority for noise regulations rests with the local government.
Return to Top
1National Renewable Energy Laboratory, NREL/FS-5J00-67440, April 2017,
Return to Top