Founder | BPI® Energy Auditor Certified Professional

An increasing number of people worldwide are moving towards a greener, more sustainable way of life. Many homeowners choose to implement solar technology, but which is better—active or passive?

Let’s take an in-depth look at passive and active solar power, how you can use them in a home, and the key differences that put one above the other.

Table of Contents

Which is Better, Active or Passive Solar Technology?

Active solar technology is ultimately more effective than passive. While passive solar power can only control the temperature in a home, active solar power can extend to heating water and producing electricity to power a home. Active has a broader reach and is more eco-friendly.

What Is Passive Solar Technology?

Solar passive technology uses thermal mass to absorb and distribute the sun’s heat throughout a home. A home with a passive solar design can harness air movement to control the temperature, cooling it during hot weather and heating it during temperature drops.

The primary advantage of passive solar heating is that it replaces electronic heating and cooling systems. This alternative takes a tremendous amount of stress off of the power grid, lowering your carbon footprint.

What’s more, your monthly electric bill will come in significantly lower than it would have with traditional heating and cooling methods.

In fact, designing a passive solar home is cheaper than a traditional home, as you don’t need to pay to install costly cooling systems.

To better understand the merits of passive solar design, let’s look at how this kind of design works.

How Passive Solar Design Works

Solar passive home design relies heavily on environmental factors like:

Sun exposure – every passive solar home is built to optimize the sun’s heat. If the climate is relatively cold or the house is designed awkwardly, the whole system is null.
Foliage and shade – passive solar homes require total sun exposure, so any vegetation, trees, or structures that shade the house must be removed.
Zoning laws – checking your local zoning laws before building a home alerts you to any potential future construction that could jeopardize your home. For example, a factory going up next to your home and blocking the sunlight would be disastrous.

Solar passive design works on four basic principles, including:

Aperture
Thermal mass
Distribution
Control

These principles control heat absorption and distribution throughout a home in a delicate yet effective system.

Aperture

The aperture controls how the sun’s heat and light enter a space. Aperture features include windows, glass doors, sunroofs, etc.

The interior of a passive solar home with the sun shining in brightly through a floor-to-ceiling set of windows

In the summer, these components collect indirect heat and avoid direct sun to prevent overheating. However, they are exposed to direct sunlight in winter to utilize as much natural heat as possible.

Thermal Mass

Thermal mass materials absorb sunlight and external heat during the warm season and warm air from inside the living space during the cooling season. These are the items that absorb and distribute heat when there is a drop in temperature.

Typical thermal mass items include dark flooring or concrete slabs. The most effective thermal mass is water, so some choose to have a water tank in their living space. However, this isn’t always an accessible choice.

The three absorption methods include:

Direct gain – the living space contains a thermal mass to absorb heat, such as a water tank or exposed brick walls.
Indirect gain – there isn’t an item within the living space that absorbs heat. Instead, heat gathers at the window and disperses through a living area using conduction. The most popular choice is a Trombe wall.

Closeup on the gap between a Trombe wall and exterior south-facing windows in a passive solar home — Courtesy of Mr Bim Architects

Isolated gain – sunlight pools in a dedicated room called a sunspace which can be cut off from the rest of the house.

Distribution

Distribution refers to how the home’s structure lends itself to airflow and dispersing heat through the space.

The three main methods of distribution include:

Radiation – warmth is stored in an object and radiated outwards, the way you’d feel the heat coming out of an oven when you open it.
Convection – the sun’s heat concentrates in some regions of the house, and air or water disperses this heat.
Conduction – heat transfers through things that are in direct contact with each other. For example, touching a warm brick wall will warm your hands.

Control

Control uses features of a house to mitigate intense sunlight during summer, stopping concomitant overheating. This control typically comes from awnings, pergolas, blinds, and other mechanisms that shade windows.

Note that these shouldn’t stop sunlight from directly heating the house itself, just from coming straight through the windows into the living space.

Solar panels installed as a window awning to create a more eco-friendly plastic window — A solar panel awning is a passive and active solar one-two punch.

During winter, sunlight should come directly through the windows to maximize heating. This consideration is why passive solar designs are so particular—they rely on perfect positioning concerning the sun’s movement to control the temperature throughout the year.

Disadvantages of Solar Passive Design

We’ve looked into passive solar design and how it benefits the environment and your bank account.

However, there are a few limitations to passive solar technology, including:

Particular design – the reality is that this technology relies on planning a design down to the most minor details, all of which depend on the sun. This reliance means no foliage in certain areas, and you cannot plan the layout as freely as you would a regular home.
Construction cost – though this design saves a big chunk of money in the long term, it costs a pretty penny to build because of all the minute details.
Limited power – passive solar technology controls heating and cooling, but that’s about it. It doesn’t involve producing electricity or heating water like active solar technology.

Building your dream solar-efficient household is a tall task, but you can start by contacting one of these green home builders in Montana. This state is ideal for green homes that rely on sunshine due to its sprawling landscapes and agreeable weather.

What Is Active Solar Technology?

Solar active technology “gathers” the sun’s energy using semiconductive materials and stores it. This energy is later converted to heat or electricity that can power a home, heat water, and act as a natural heating mechanism.

Unlike passive solar, active solar makes use of solar or photovoltaic panels. Solar panels convert the sun’s energy into heat, and photovoltaic panels convert the sun’s energy into electricity.

The clay tile roof of a home retrofitted with a solar panel array

Using one or the other, or a combination of the two (seeing as homeowners can easily use them in conjunction with one another), allows a home to become energy-efficient in its own right, with little to no need for electricity from the grid.

Right off the bat, it’s evident that active solar is functionally superior to passive. It enables you to harness the sun’s natural energy to power your lights, boil water, and heat your home.

Relying more on natural energy sources and less on grid electricity brings you closer to a net-zero home. A net-zero home produces as much energy as it uses throughout the year, creating congruous consumption and output.

Net-zero housing generates its own power to reduce stress on the grid and alleviate our society’s heavy reliance on fossil fuels, the burning of which has disastrous effects on our planet.

As time goes by, solar energy solutions become more and more affordable and accessible to the general public, allowing more individuals to migrate towards a more sustainable lifestyle.

Read more about net-zero living and sustainable home design, here.

How Active Solar Design Works

Active solar technology allows us to store and use the sun’s energy for multiple purposes. We do this using conductors that convert energy into heat or electricity.

These two technologies include:

Solar-thermal collectors
Photovoltaic panels

Let’s look at each of these in greater detail.

Solar-Thermal Collectors

The sun’s radiation is absorbed using large plates or panels on the home’s roof and stored in water or a glycol-water solution. This water heats up, and the heated water flows out when a tap is turned on.

A solar heat pump water heater with orange trim on a beige floor.

The outgoing hot water is replaced by incoming cool water, which becomes hot, and the cycle will continue.

This technology comes in two types:

Flat – a flat metal plate connects to a pipe system insulated with mineral wool.
Vacuum – several insulated pipes that carry heat from the sun to water stored in an exchanger.

This process may sound familiar, and that’s because it is. Home geysers employ this same method of heating water, the critical difference being those solar-thermal collectors complete this process using the sun’s energy, not electricity.

Read more about the differences between solar water heating and electric geysers, here.

Photovoltaic Panels (PV Panels)

Silicon photovoltaic panels are placed on top of a home’s roof. The electricity they produce feeds into an inverter, which converts the direct current to alternating current, allowing this electricity to be used straight from outlets in the home.

PV panels are more effective than solar-thermal ones. Solar-thermal collectors can become stagnant if left dormant for long periods.

As you can see, PV panels produce electricity that can power a home, producing around 120 volts. Using this alternative energy source and power from the grid conservatively, you can reduce your energy usage by about 9 kWh/day.

Additionally, PV panels return any excess electricity generated to the power company to store over the colder months, saving you electricity in the long run.

There are two categories of PV panels:

Monocrystalline – cut monocrystalline silicon with a uniform black or inky blue color. These are highly efficient, withstand extreme conditions, and have a longer lifespan than polycrystalline cells.
Polycrystalline – a combination of many mono-crystals, these light blue speckled cells are less efficient per square foot and are more vulnerable to extreme conditions than their monocrystalline counterparts.

You can view a complete and concise comparison of monocrystalline and polycrystalline PV panels, here.

PV panels are made by compiling numerous monocrystalline or polycrystalline cells in the form of square sheets. These sheets are made by crushing and melting silicon crystals in a lab, then assembling several “wafers” or strips into one square formation.

An off-grid PV hydro-powered active solar tassie

Monocrystalline cells are cut from conical silicon ingots, so they’re made with rounded corners to minimize material waste. Polycrystalline cells have a sort of marbled color which comes about during the cooling process, during which it crystallizes.

Because of this, monocrystalline cells are more expensive to make and result in more wasted material.

Advantages of Active Solar Technology

Solar active technology is a wonderful way to live for the eco-conscious without having to break the bank every month by simply maintaining the system.

Some of the various advantages include:

Sustainability – active solar technology is an invaluable resource for those who are making a move to a more sustainable lifestyle. It significantly reduces your reliance on grid power and fossil fuels, reducing your carbon footprint.
Finances – in addition to treading more lightly on the earth waste-wise, active solar technology can save you significant money on your monthly electrical bill.
An excellent investment – if you ever decide to sell your eco-home, know that solar technology adds value to the property, so long as you have the rights to it.
Future energy savings – because active solar allows you to store energy, you not only save money on current electric bills but future ones too.
Comfort – active solar living has all the amenities of traditional living with far less environmental impact.

Learn more about active solar technology’s value to your home and the factors to consider at AttainableHome.com.

Disadvantages of Active Solar Technology

Despite the overwhelming advantages of using a renewable resource like solar energy, there are a few limitations and that go along with it.

Active solar drawbacks include:

Cost – though active solar technology saves money in the long run, installing all the necessary components from the offset costs quite a bit. Expenses include wiring, inverters, buying and installing solar or PV panels, and maintenance on these systems.
Weather dependence – solar technology is hardy and versatile but can only operate effectively in sunny climates.
Space and appearance – thermal collectors and PV panels take up space on roofs and can become an eyesore over time. Furthermore, some roofs don’t have the space to accommodate the necessary amount.

Final Verdict: Passive vs. Active

Passive and active solar methods both have their benefits and limitations. Passive is more financially accessible than active, but active is more versatile and powerful. Both provide energy-efficient alternatives, but active solar technology is more effective.

This leads us to conclude that active solar technology is the better of the two. Homeowners can add solar-thermal collectors and photovoltaic panels to any building that can physically and spatially support them, as long as the accompanying internal systems are geared up correctly.

Active solar power provides various functions beyond what passive has to offer. It goes beyond heating a room and can allow you to live off of independent, renewable energy.

While active solar energy costs more money to maintain, also it saves more. It becomes a long-term investment that adds value to your home while allowing you the creative design freedom that passive houses can’t afford.

Conclusion

Active solar design is less conditional, allows more creative freedom in a home’s design, and is significantly more stable and reliable than passive design as it can accommodate colder climates better.

The initial cost is relatively high, but the eventual reward is significant enough that the price is worthwhile for those who can afford it.

Home Tech Battle: Passive vs. Active Solar (Which Is Best?)