The Sun — a Reliable Source of Energy
Sun Across America
The United States is well suited for the use of solar power. Most of the nation is exposed to high levels of irradiation every day. Even in parts of the country confronted with rainy summers and dark winter months, solar power can still be put to use economically.
Ample Sun throughout the Nation
Depending on the location, the average annual energy exposure ranges from approximately 950 to 2,150 kWh/m². This broad range reflects the diversity of American climates — from the sun-drenched Southwest to the more temperate Northeast. Even regions with moderate sunlight can support viable photovoltaic installations when systems are properly designed.
| Region | Typical Annual Irradiation (kWh/m²) |
|---|---|
| Southwest (AZ, NM, NV, CA deserts) | 1,800 – 2,150 |
| Southern & Central Plains | 1,500 – 1,900 |
| Southeast & Mid-Atlantic | 1,300 – 1,700 |
| Midwest & Great Lakes | 1,100 – 1,500 |
| Northeast & Pacific Northwest | 950 – 1,300 |
Types of Solar Systems
Solar energy can be harnessed through two primary approaches, each suited to different applications:
Photovoltaics
Photovoltaic (PV) systems convert sunlight directly into electricity using semiconductor materials. They work with both direct and diffused sunlight, making them effective even under cloudy skies. PV is the technology behind SMA's inverter product lines.
Solar Thermal
Solar thermal systems capture the sun's heat to warm water or air for residential and commercial use. These systems rely primarily on direct sunlight and are commonly used for domestic hot water and space heating.
Direct vs. Diffused Sunlight
Understanding the difference between direct and diffused sunlight is key to evaluating a site's solar potential:
- Direct sunlight reaches the earth's surface without obstruction — essential for concentrating solar thermal systems and optimal PV output.
- Diffused sunlight is scattered by clouds, haze, or atmospheric particles. Modern photovoltaic modules can still generate meaningful power from diffused light, which is why solar remains practical in less sunny climates.
Both forms contribute to the total irradiation figures cited above, and a well-designed PV system accounts for the local balance between them.
Solar power systems are designed to capture the sun's energy and convert it into usable electricity through photovoltaic technology. The core components include solar panels, which contain cells that generate direct current electricity when exposed to sunlight, and an inverter that transforms this into alternating current for household or commercial use. A well-designed system can supply a significant portion of a building's energy needs, reducing dependence on fossil fuels and lowering utility costs over time. Modern solar installations are durable, require minimal maintenance, and can be customized to fit various roof types and energy consumption patterns, making them a practical choice for homeowners and businesses alike.
How Photovoltaics Work
Photovoltaic cells — typically made from silicon — absorb photons from sunlight and release electrons, creating a direct current (DC). An inverter then converts this DC into alternating current (AC) suitable for household use or feeding into the utility grid. SMA, as the world's leading manufacturer of PV inverters, produces devices that maximize this conversion efficiency while providing robust monitoring and data communication capabilities.
How Solar Thermal Energy Works
Solar thermal collectors absorb sunlight and transfer the resulting heat to a fluid — typically water or a water-glycol mixture. This heated fluid is then circulated to a storage tank or directly to a heating system. Common applications include domestic hot water, pool heating, and space heating in residential and commercial buildings.