As the demand for renewable energy continues to grow, homeowners are increasingly exploring solar energy to reduce their carbon footprint and lower energy costs. Solar energy is not just one-size-fits-all—there are two primary approaches:
Passive Solar: where you design in strategies to use the ‘free’ heat from the sun.
Active Solar: a mechanical system that allows you to harness thermal or electrical energy from the sun for use in a building.
Understanding the differences between these systems is essential when considering the best solution for your home.
What is Passive Solar Energy?
Passive solar energy is a design approach that maximizes the power of the sun for heating, cooling, and lighting in a building without mechanical devices. The solar component is baked right into the fabric and design of the building. It relies on the orientation and space planning of the building to take advantage of natural solar energy.
How Passive Solar Design Works
Passive solar systems rely on a building's design to collect, store, and distribute solar energy. This can include positioning windows to face south (in the Northern Hemisphere) to capture maximum sunlight during the winter months, using thermal mass (such as concrete or stone) to store heat, designing the building to take advantage of natural ventilation for cooling and air movement, as well as using shading and insulation to regulate indoor temperatures.
Integrating Passive Solar into A House
Passive solar design is relatively easy to integrate into the construction of homes, particularly in climates where heating is a significant concern. For example, homes can have windows that are carefully sized and situated to allow for heat collection and natural ventilation. Materials such as concrete floors or thick brick walls can store heat during the day and release it slowly during cooler nights.
One of the key parts of passive solar design is ‘store’: making sure the heat that is collected through the windows stays inside the building envelope. An airtight envelope with high insulation levels make the best storage device for solar energy in a house.
Pros and Cons of Passive Solar Design
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Disadvantages: |
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Low-cost implementation, especially if integrated during the home’s construction. |
Limited ability to control temperatures compared to active systems, especially in extreme weather. |
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No need for additional mechanical systems or ongoing maintenance. |
Effectiveness is highly dependent on building orientation, window placement, and climate. |
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Reduces energy consumption by naturally moderating temperatures. |
Retrofitting an existing home to incorporate passive solar design can be challenging and costly. |
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Environmentally friendly, as it relies solely on natural sunlight without electricity or fuel consumption. |
What is Active Solar Energy?
Active solar energy systems use mechanical or electrical devices to capture, convert, and distribute solar energy. These systems typically involve solar panels, pumps, or fans to collect and circulate heat or electricity. Active solar is most commonly associated with photovoltaic (PV) panels, which convert sunlight into electricity.
Two Types of Active Solar Energy Systems
There are two ways to extract energy from sunlight. The first type creates electricity from ‘semi-conductor’ materials that create electrical charges. The second type works on the same principle as passive solar: it collects, stores, and distributes the sun’s energy as heat.
Active solar systems are used for electricity generation, heating, cooling, and water heating.
Active solar systems rely on panels, typically installed on the roof or in other sunny locations, to capture sunlight. Solar panels use Photovoltaic (also known as PV) cells to convert sunlight into electricity.
Active solar systems that produce thermal energy use panels or tubes as solar collectors that heat fluids or air, which is then stored and circulated via piping or ducting.
Pros and Cons of Active Solar Energy Systems
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Disadvantages: |
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High efficiency in converting solar energy to electricity or heat. |
Higher initial costs due to the need for solar panels, batteries, and other equipment. |
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Can dramatically reduce or eliminate reliance on grid electricity. |
Potential dependence on grid electricity during extended periods of low sunlight unless a battery storage system is in place. |
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Scalable to meet the energy needs of homes of varying sizes. |
Requires regular maintenance of mechanical components, like pumps and inverters. |
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Ability to store energy in batteries for later use, providing reliability even on cloudy days. |
4 Key Differences Between Active and Passive Solar
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Energy Capture: Active systems use mechanical or electrical components to capture and distribute solar energy, while passive systems rely on building design and materials to harness sunlight naturally.
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Cost: Active solar systems require a significant upfront investment for equipment and installation, while passive solar systems can be more affordable, particularly if planned during the home’s construction.
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Maintenance: Active systems need ongoing maintenance for mechanical parts like inverters, pumps, and batteries. Passive systems, on the other hand, have minimal maintenance requirements as they rely on static building features.
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Control: Active systems offer greater control over energy output and storage, making them more adaptable to changing weather conditions. Passive systems depend entirely on the design and natural environment, making them less versatile.
What is the best type of energy for a house?
Both active and passive solar energy systems offer valuable ways to harness the power of the sun.
Clean energy, like solar power or wind power, gives individuals and society a leg up when it comes to minimizing energy usage. A solar energy system to produce electricity is more common than wind for homes, because a home solar electric system can be installed on the roof, and doesn't have any moving parts.
Passive solar does that at the design stage, so it’s definitely worth it to spend some time figuring out seasonal design features for new builds and renovations. Gather the sun’s heat to keep the interior of the house warm and deflect or reject it to keep the house cool.
Can you power your entire home with solar?
Absolutely.
That’s what the terms ‘net zero energy’, or ‘zero net energy’ refer to: houses that produce as much energy in a year as they consume. Most often, the cost effective solution is to power home with solar panels.
Solar electric systems are a good match for electrification projects where oil or gas furnaces and boilers get switched out for heat pumps. Electrification programs aim to minimize greenhouse gas emissions by reducing reliance on fossil fuels.
Active solar gets ‘bolted on’, but there still needs to be planning for orientation as well as roof size and shape to optimize a solar PV system. Management of occupant loads becomes more crucial the closer the house gets to Net Zero Energy targets.
What is the Cost of Solar Panels?
Solar panels cost money. There's no way around that. Installation costs have come down significantly over the past decade, and most experts agree that if panels are installed for $3 per Watt, there is a reasonable payback the system, based on the average costs of electricity provided by the regional utility company.
There are a range of tax credits and financial incentives for green energy that can help reduce the costs of installing solar panels.
Minimize Loads, Maximize the Investment
It's important to minimize occupant loads and create a high performance building envelope for an all-electric building brimming with energy efficiency features. Making sure the system is optimized for energy production falls to the solar company installing such a system. Look at at future energy costs, a house that generates it's own electricity is immune to price swings and, potentially, grid outages, as well.
The more the annual electricity usage goes down, the fewer solar panels needed. Energy production needs to be optimized at the design stage. One thing homeowners can do right now is look at their utility bills and see how much electricity they are using. It's relatively easy to translate energy costs associated with gas and oil use into equivalent kilowatt hours to see how much power they would use in their current situation.
Solar Panel System Components
A solar panel setup includes the collector panels, and then what's commonly called the 'balance of system', often shortened to BOS. Going with high quality solar panels with good efficiency ratings is the best investment, as more power will be generated with the same number of panels. In a grid-tied system, the next biggest expense after the panels themselves is the inverter. Net metering systems need inverters that meet utility company requirements for connection.
After installation, there are minimal maintenance costs and no moving parts.
Number of Panels
How many panels are required to generate enough electricity to bring a house to a net zero energy target is based on a few factors. First, the actual location of the house. Sunlight hours vary significantly across the continent. Second, the roof orientation, because that affects how much sunlight gets converted. Third, the pitch of the roof. Fourth, the amount of shading on the roof.
The location of the house, the roof orientation, the shading and the pitch of the roof determine how much electricity can be generated.
The power usage of the house will determine if a rooftop installation can completely power the house or not. If there is not enough power generated, look to higher efficiency panels for more energy, or ways to reduce the energy usage to fit the rooftop installation. In some areas, excess solar energy can be sold back into the grid to further reduce electricity costs. In other areas, more solar panels are not allowed. Systems can also be set up to charge (and be charged by) an electric vehicle.
Building Codes Are Moving to Net Zero
Building codes are moving us down the path to Net Zero Energy by 2050. Electrification and renewable energy systems are how we get there, once we've improve the building envelope.
Active solar is ideal for homeowners seeking higher efficiency and control over energy generation, while passive solar is a cost-effective, low-maintenance solution for energy savings through thoughtful design. The choice between the two depends on your energy needs, budget, and whether you're building a new home or retrofitting an existing one.
We say there's no need to choose between the two. Passive solar design reduces the amount of energy usage in a home and reduces reliance on fossil fuels. That can lead to an optimized load for an active system to provide enough electricity for the home via a rooftop installation. Both passive and active systems have great environmental benefits and combat greenhouse gas emissions.
Why not use both?
Learn more about passive and active solar (and wind) in our Renewable Energy Sources for Housing Course.
