Toaster Ovens' Versatility Makes Them Slower And Less Convenient Than Slot Toasters

What They Have In Versatility, They Sacrifice In Convenience, Speed, And Precision

How Design Differences Between Toaster Ovens and Toasters Affect Toasting Performance

The Simple, Effective Design of a Slot Toaster

Slot toasters may be simple, but their design is highly optimized for making toast quickly and evenly. With heating elements positioned close to both sides of the bread, they provide intense, direct radiant heat that ensures fast browning. Their simple controls allow users to easily adjust the level of doneness, and the spring-loaded mechanism automatically ejects the toast once completed. The design of the toaster has remained largely unchanged for decades and consists of the following:

1. Outer shell
2. Levers
3. Timer (electronic or bimetallic)
4. Spring-loaded carriage
5. Resistive wire heating elements
6. Electromagnet

When the lever is depressed, the carriage lowers the bread while side rails hold it in place. The heating elements and electromagnet activate, locking the carriage down as toasting begins. Browning controls adjust the toasting time, either via a bimetallic thermostat in older models or a digital timer in newer ones. When the cycle ends, the heaters turn off, the electromagnet releases, and the toast pops up.

Toaster Ovens are Small Ovens Designed to Toast Well

A toaster oven is very similar in terms of design to a full-size oven, just small enough to fit onto a countertop. The name "toaster" comes from the fact that they feature upper and lower heating elements in close proximity to the cooking tray, making them effective at quickly browning foods. They consist of the following components:

1. Outer housing
2. Cooking chamber
3. Glass door
4. Heating element
5. Controls
6. Temperature sensor
7. Fan and motor (in convection models)

In a toaster oven, the upper and lower heating elements generate the radiant heat needed for toasting while also warming up the cooking chamber. The controls allow users to switch between cooking modes like bake, broil, and toast, which determines which heating elements are activated. Toaster ovens also feature both temperature and time controls to regulate cooking.

In toast mode, the temperature is preset to a high "toast" setting, acting as a safety cap rather than a precise cooking temperature. This means the elements will remain on for almost the entire toasting cycle, only shutting off if the internal temperature exceeds 500–600 °F, which typically doesn't happen under normal operation. Essentially, this allows the heating elements to stay active throughout the entire duration of the toasting cycle.

The timer determines the level of toasting. Most toaster ovens use a simple dial or digital timer marked with toast shade indicators, usually coinciding with a range of 0 to 10 minutes, to help users achieve their preferred browning level.

A more in-depth design study of toaster ovens can be found in our article comparing toaster ovens to full-size ovens.

How Heating Elements and Heat Transfer Differ in Toasters and Toaster Ovens

The heating elements in toasters consist of parallel rows of resistive wires on insulating sheets along both sides of each slot. As current flows through these wires, they glow red-hot and provide direct radiant heat to both sides of the bread simultaneously.

Parallel wires distribute heat evenly, while the spring-loaded carriage centers the bread, keeping the elements 1–1.5 cm away. This close distance allows the elements to quickly and efficiently transfer heat, ensuring fast and even browning.

Conversely, toaster ovens use either Calrod™ or quartz heating elements in a tubular format (we also go more into depth about the difference between these heater types in our article comparing toaster ovens to full-size ovens).

There are usually between 2 and 6 of these elements, and they're located equally above and below the toasting rack. However, the elements are much farther away in a toaster oven—typically between 4–8 cm (1.5–3.1 inches). This greater distance significantly reduces the intensity of the radiant heat, meaning the bread receives less direct energy compared to a slot toaster.

The reduction in heat follows the inverse square law, which states that radiant energy intensity decreases with the square of the distance:

Radiant heat weakens quickly as distance increases. The closer the bread is to the heating elements, the more intense the heat it receives and the faster it toasts. Thus, even toasting requires a careful balance between heater spacing and distance from the bread:

• If the heaters are spaced too close together, more radiant heat will concentrate on the innermost slices, causing hotspots.
• If spaced too far apart, the radiant heat may be wasted through the glass door or into the cooking chamber's metal walls.
• If the heaters are too close to the bread, they will not evenly distribute radiant heat onto multiple slices.
• Too far away, and the intensity is reduced so much that toasting takes an extremely long time.

The graphic below roughly illustrates this concept:

An example of this uneven heat distribution can be seen in the Panasonic FlashXpress NB-G110P, where the lower edge of the toast (closest to the glass door) is left under-toasted:

Now that we have a basic understanding of how toasters and toaster ovens generate and transfer heat, we can better explain how these design choices impact real-world toasting performance.

Performance Testing Between Toasters and Toaster Ovens

Image Analysis for Toasting Evenness

Our toast analysis journey started in October 2023 when we started working on the launch of our toaster reviews. We developed a method to objectively measure the evenness of toast via image analysis. A photo cube was designed to take overhead photos of toast against a green background, with even lighting to ensure consistency regardless of ambient lighting changes in the lab.

To perform the image analysis, we developed a Python script that begins by extracting the toast slices from the green background. Then, it converts the image to grayscale and assigns a pixel intensity value (from 0 to 255), which corresponds to different levels of browning. A mean pixel value of around 180 is expected for untoasted bread, while a mean pixel value of 60 showcases charred or burnt toast. The graphics below explain the process:

This code analyzes one slice of toast at a time. Since some toaster ovens toast up to nine slices simultaneously, the Python code was adapted to analyze the upper and lower faces of all slices in a single photo for each face:

Our toaster R&D article provides a more in-depth explanation of our image analysis.

Both Toasters and Toaster Ovens Deliver Even Toast

Toasters and toaster ovens both produce evenly toasted batches, with only slight differences in performance. In fact, even the lowest-performing toasters produce less even toast than the lowest-performing toaster ovens. Overall, toaster ovens achieve an average evenness score of 7.9, compared to 7.8 for toasters—a nearly identical result.

Since toaster ovens can often accommodate more than four slices, we conducted two tests: one to assess their maximum capacity toasting performance and another to evaluate their performance with just four slices, allowing for a direct comparison with four-slot toasters.

When using the maximum rack surface area, toasting doneness varies more—especially along the lower edges, where radiant heat can bleed through the glass door. Heat also tends to concentrate toward the center of the cooking chamber, leaving the outer edges of the bread less toasted.

As more slices are added, evenly heating each bread face becomes more challenging, as seen when comparing the average performance of four-slice toasting with max-capacity toasting:

Regardless, if you're used to having a four-slice toaster and don't need to toast additional slices in a single batch, almost every toaster oven we tested delivers similar four-slice performance—even the larger models that offer the added benefit of large capacity for higher-volume cooking tasks:

For example, the Ninja Foodi DT201, which can fit a maximum of nine slices, offers nearly identical four-slice toasting performance to that of our most even four-slice toaster:

However, while the Beautiful 4-Slice Toaster with Touch-Activated Display does this in 2 minutes and 15 seconds, the Ninja takes over double the time at 5 minutes and 25 seconds.

Toasters are More Efficient

While the performance between toaster ovens and slot-toasters is very similar from an evenness perspective, slot-toasters have a huge advantage when it comes to speed. As discussed in the design section, the vastly higher distance between the heaters and the bread in toaster ovens means that the rate at which radiant energy is transferred is substantially slower.

As the table shows, the speed is correlated with size. While toaster ovens with larger cooking chambers can accommodate taller food items and are useful for processes like baking or roasting, the added height and overall volume of the cooking chamber have a negative impact on toasting time.

Even the fastest 4-slice toaster oven we tested, the Panasonic FlashXpress, which takes 2 minutes and 55 seconds, is slower than all but one slot-toaster, the Breville Die-Cast 4-Slice Smart Toaster, which clocks in at 3 minutes and 7 seconds.

That being said, there is a case for time savings when considering the larger batch size that larger toaster ovens can handle. The Ninja takes 05:25 to produce nine slices of evenly browned toast. In comparison, the average four-slice toaster takes 02:24 to make four slices:

While the time per slice is still faster with the average four-slice toaster, the advantage shifts when considering the need to reload the toaster for larger batches. Factoring in the time it takes to remove the toast and insert a new batch—toaster ovens can be a more efficient and convenient option for making larger batches of toast.

From an energy perspective, toasters are also significantly more efficient. The four-slice toasters we tested used an average of 76 Wh or 19 Wh per slice. In comparison, toaster ovens used an average of 136 Wh to make four slices or 34.1 Wh per slice—making toasters nearly twice as energy-efficient for the same task.

Toasters Offer Better Toasting Control Than Toaster Ovens

Another area where toasters outperform toaster ovens is in their toasting range control. Most toasters offer settings from 1 to 5, with some models reaching 7 or higher. Toaster ovens feature similar settings, but the differences between those settings are often minimal—especially in larger models.

In most larger toaster ovens, the first 4–5 settings have very little difference. Typically, they will only produce golden brown toast at the highest setting, so you'll need to run an additional cycle if you want dark toast. Conversely, slot toasters typically produce a wide range of toast, ranging from barely warmed to thoroughly charred:

For a more direct comparison of range control, we selected the BALMUDA The Toaster—the best-performing toaster oven we tested for precise range control:

This model has a performance comparable to most slot-toasters for precision range control. However, it is the second-smallest toaster oven we tested and can only fit two slices of bread. While it does offer excellent range control, its small size makes it difficult to use for other typical toaster oven tasks.

Most users may find the range provided by toaster ovens sufficient. But for those who frequently fine-tune toast for different applications—or simply prefer toast on the darker, charred side—a slot toaster will almost always be the better choice.

Conclusion

While limited in versatility, a slot toaster's simple, optimized design quickly delivers evenly browned toast with precise shade control. If you regularly make toast, it's hard to beat the toaster's small footprint, quick performance, and energy efficiency. For a deeper dive into how we developed our image analysis method to objectively measure toaster performance, check out our Toaster R&D article and watch our video about our toaster testing process.

Toaster ovens, while slower, larger, and less efficient, can be an alternative for larger batches of toast and can provide similar levels of evenness to a toaster, provided you choose the right model. However, when it comes to large quantities of toast, commercial conveyor toasters are already designed to handle multiple slices quickly and consistently, so toaster ovens don't offer any real advantage for toasting over existing products. That said, toaster ovens offer a slew of other cooking methods beyond toasting, including baking, reheating, and, in some models, air frying, making them one of the most versatile countertop appliances available.

To learn more about how toaster ovens compare to other kitchen appliances, check out this article in which we explore the air frying performance of toaster ovens versus basket-style air fryers. We also have an article that shows how a toaster oven fares when compared to a standard, full-size oven.