5 Key Factors to Keep in Mind When Constructing a Solar-Powered Home

Essential Insights

Over the past decade, rooftop solar installations have transitioned from being a rarity to a mainstream choice. This shift is highlighted by Home Depot's move to begin selling solar panels in 2001 [source: DOE].

The technology has existed for decades—NASA has utilized solar-powered satellites since the 1960s, and passive solar heating systems, which convert solar energy into heat rather than electricity, have been employed in U.S. homes as early as World War II [sources: Southface, DOE].

However, integrating active solar systems into the mainstream residential market has been challenging. Active solar power relies on photovoltaic cell arrays to transform sunlight directly into electricity, a technology historically deemed too costly for widespread adoption.

The advantages of residential solar power are clear: solar energy is virtually inexhaustible (for the next 5 billion years, approximately), produces clean energy without greenhouse gas emissions, and can significantly reduce electricity costs [source: APS]. However, determining if solar power is right for you involves more than just evaluating the price.

This article explores five critical factors to consider when contemplating an investment in a residential solar-power system. While harnessing photovoltaic energy is an eco-friendly and potentially cost-effective decision, it’s not as simple as relying on the conventional electrical grid.

The first factor to consider might surprise you: What maintenance is required for the solar panels once they’re installed on your roof?

5. Maintenance

Using solar energy to power your home involves slightly more upkeep compared to relying on traditional grid electricity. However, the maintenance required is minimal.

Solar panels are designed without moving parts, making them part of a fully static system. Once installed, there’s little that can malfunction. The primary responsibility for homeowners is to ensure the panels remain clean. This is crucial, as excessive dust or bird droppings can block sunlight, potentially reducing the system’s electricity output by up to 7 percent [source: CalFinder].

This maintenance doesn’t need to be frequent—cleaning the panels with a hose from ground level, just one to four times a year, is typically sufficient [source: CalFinder]. However, if there’s ongoing construction nearby, more frequent cleaning may be necessary to prevent dust buildup from affecting performance.

Beyond cleaning, occasional inspections are necessary to ensure all components are functioning properly. Over time, you might need to replace the inverter or, if applicable, the batteries in a storage system, though such replacements are rare, typically occurring once every ten years.

Next up: Do you have many trees on your property?

4. Surroundings

The location of your home significantly impacts the efficiency of your solar-power system. It’s a straightforward issue: since solar power relies on sunlight, obstacles like tall trees or nearby buildings that cast shadows can hinder performance.

The impact of shade on solar panels is more significant than many realize. Different panel types respond differently to shading. For instance, poly-crystalline panels experience a notable drop in output when partially shaded, whereas mono-crystalline panels cease generating electricity altogether under similar conditions.

To maximize solar power efficiency, it’s crucial to ensure that no shadows fall on the roof’s panel area during peak sunlight hours (usually between 10 a.m. and 2 p.m.), and ideally throughout all sunny periods [source: AEG]. The longer the panels are exposed to direct sunlight, the more effective they are at generating power.

Optimizing efficiency may require trimming or removing trees on your property to prevent shading. If tall buildings nearby block sunlight from reaching your roof, this poses a more challenging issue to resolve.

This leads us to the next critical factor: sunlight availability.

3. Insolation Rating

Sunlight is undeniably crucial for solar power, and its availability varies significantly by region. Understanding the amount of sunlight that reaches the ground in your area is essential when planning a solar-powered home.

The concept here is insolation—a metric that quantifies the amount of solar radiation reaching the ground in a specific area over a set time frame. Measured in kWh/m2/day, it indicates the sunlight available for your solar panels to convert into electricity. Higher insolation values mean greater electricity generation per panel, allowing for fewer panels to meet your energy needs. Conversely, lower insolation values may require more panels to achieve the same output, potentially increasing costs (more on this later).

Residents of cities like Phoenix, Arizona, or Albuquerque, New Mexico, benefit from exceptionally high insolation ratings—6.58 and 6.77, respectively [source: CleanBeta]. In Albuquerque, for example, 6.77 kWh of sunlight hits each square meter daily on average. In contrast, Portland, Maine, receives 4.51 kWh/m2/day, while Chicago gets only 3.14 kWh/m2/day [source: CleanBeta].

Does this mean solar-powered homes are only viable in the Southwest? Not necessarily. It simply implies that a solar system in Chicago will be less efficient than one in Albuquerque. To achieve the same energy output, more panels may be required in areas with lower insolation.

This leads us to the second key consideration: determining the number of panels required.

2. Coverage Area

Contrary to popular belief, the scale of a solar-power system isn’t determined by the size of the home it powers.

Instead, it hinges on two factors: insolation, as previously discussed, and your energy consumption. For instance, a resident of Albuquerque with low energy usage will require a smaller system, while someone in Chicago running an outdated electric furnace constantly will need significantly more panels to meet their energy demands.

To estimate the size of the solar system you require, check your electricity bill to determine your daily kWh usage. The average U.S. household consumes approximately 900 kWh per month, or 30 kWh daily [source: DOE]. Multiply this by 0.25 [source: GE], resulting in 7.5, indicating a need for a 7.5 kW system.

A standard solar panel generates up to 120 watts, or 0.12 kW, per day [source: Richards]. For a 7.5-kW system, you’d need around 62 panels. Each panel typically measures about 56 by 25 inches (142 by 64 centimeters), meaning a 62-panel setup would occupy roughly 700 square feet (65 square meters).

However, this calculation involves additional factors. You must account for insolation, peak sunlight hours per day, and adjustments if using a battery-storage system. Consulting a professional is advisable for precise planning.

Assuming this is the approximate system size needed to power your home, what would be the financial investment for a 7.5-kW solar setup?

Next, we address perhaps the most critical factor: the cost.

1. Expense

In 1956, the cost of solar panels was approximately $300 per watt [source: Southface]. At that price, a 7.5-kW system would have been unaffordable for all but the wealthiest individuals.

Today, prices have dropped significantly. Solar arrays typically cost between $7 and $10 per watt, depending on whether you opt for a DIY installation (closer to $7) or hire a professional (closer to $10). For a 7.5-kW system (7,500 watts), the total cost could range from $50,000 to $75,000.

If your energy consumption is lower, the cost decreases accordingly. For instance, if you use only 600 kWh per month (20 kWh/day), a 5-kW system could meet your needs, reducing the cost to around $40,000.

Significant tax credits can substantially reduce the overall cost. For example, in New Jersey, homeowners purchasing a $50,000 system can receive a $12,500 state rebate in addition to an $11,000 federal rebate, bringing the total cost down to $26,500.

It’s worth noting that solar power doesn’t have to be an all-or-nothing investment. You can choose to partially power your home with solar energy. For instance, a $10,000 investment in a 1.5-kW solar system can supplement your grid electricity usage.

However, even with these savings, the upfront cost of a solar array remains high, and it can take many years to recoup the investment through energy savings [source: WeatherImagery].

A recent innovation in the solar industry has made solar panels more accessible to those unable to afford the upfront costs. Companies across the country now offer solar panel rentals, eliminating the need for a large initial investment. Homeowners pay a monthly fee to use the panels, while the rental company handles ownership and maintenance, effectively removing the financial barrier.