Is an Air Fryer More Energy Efficient Than an Oven

By Ben Tasker / Developer
Nov 27, 2024

This blog was originally posted on www.bentasker.co.uk

This project was built using a previous version of InfluxDB. InfluxDB 3.0 moved away from Flux and a built-in task engine. Users can use external tools, like Python-based Quix, to create tasks in InfluxDB 3.0.

At first glance, the question I’m asking in this post almost seems redundant. An air fryer heats a much smaller area and uses a smaller heating element, so of course, it should be more energy efficient. However, that’s not guaranteed to be the case. Although an oven uses a larger heating element, because it’s better insulated, it’s possible that it might do a better job of keeping heat in and so have to consume less energy replacing lost heat. If, due to these losses, the air fryer’s element is on for a longer duration of the cook, it’s plausible that an air fryer might end up consuming more energy than the oven.

If (as seems likely) the air fryer is more energy efficient, the question becomes:

• How much more efficient?
• When does it amortize (i.e., at what point do the energy savings outweigh the initial purchase cost)?

That second question will also help answer whether it’s worth investing in an air fryer to try to counter high energy prices. To see how they compare, I cook myself some chips and compare the resulting energy usage using:

• A Rangemaster Professional oven (3.2 kWh)
• An air fryer (1700w 5.5L air fryer)

The cook

Both the oven and the air fryer cooked the same thing: Co-op’s brand of frozen oven chips. The appliances are situated in the same kitchen, but at opposite ends (so the air fryer does not benefit from heat radiating from the oven warming the air it draws in).

Although they’re cooking the same food, there are some differences:

• The oven requires 25 minutes, and the air fryer takes 15
• The oven needs to be set to 180°c (per the packaging), while the air fryer manual says to use 200°c

Unlike the oven, the air fryer doesn’t need to warm-up first, cutting 15-20 minutes off the run time (depending on how long it takes you to come back and put food into the oven).

The oven started first. When the air fryer finished, the oven was turned off and the food was removed from both.

As with my previous forays into measuring energy consumption, I collected and wrote energy usage readings using InfluxDB so I could query statistics back out with Flux.

InfluxDB is ideal for monitoring energy consumption because it’s purpose-built to handle time series data. Time series data is the type of data I’m collecting from both the oven and air fryer. InfluxDB ingests the data in real-time so I can see my visualizations immediately.

Retrieving results

Because of how it’s wired in (into its own circuit, with no convenient access to the wiring for a clamp meter), calculating the oven’s usage requires a slightly more complex query than is normally required for individually monitored appliances.

The way usage is calculated is:

1. Retrieve usage for all individually monitored devices.
2. Retrieve usage for power meter.
3. Subtract the sum of device usage from the power meter (find details on how I collect this here).
4. Subtract a known base load figure (to account for items not monitored) to arrive at the Oven’s usage.

There is a small margin for error involved in the subtraction of the base load, but it is quite small: I’ve been doing a lot of work recently to understand our base load (to find where it can be reduced).

The air fryer was plugged into a Tapo P110 Smart Socket, so its usage is easy to collect and query.

I wrote a Flux query to retrieve and combine usage data for each of the appliances into a single output stream:

// Start/Stop times
start = 2022-09-04T16:40:00Z 
stop = 2022-09-04T17:30:00Z 

// Group into 30s  time windows 
// helps ensure meter and appliance readings appear in the same window
period = 30s

// get appliance usage
known = from(bucket: "Systemstats")
  |> range(start: start, stop: stop)
  |> filter(fn: (r) => r._measurement == "power_watts" and 
                       r._field == "consumption")
  |> filter(fn: (r) => r.host != "power-meter")
  |> aggregateWindow(every: period, fn: mean)
  // Combine all appliances into a single table
  |> group()
  // Calculate the combined consumption per window period
  |> aggregateWindow(every: period, fn: sum, createEmpty: true)

// Get total usage measured at the meter
pm = from(bucket: "Systemstats")
  |> range(start: start, stop: stop)
  |> filter(fn: (r) => r._measurement == "power_watts" and 
                       r._field == "consumption")
  |> filter(fn: (r) => r.host == "power-meter")
  |> aggregateWindow(every: period, fn: mean)

// Join the two
oven = join(tables: {t1: pm, t2: known}, on: ["_time"])
  // subtract appliances + base load to get oven usage
  |> map(fn: (r) => ({
      _time: r._time,
      _field: "Oven",
      _value: r._value_t1 - r._value_t2 - 400.0
  })) 

// Get the air fryer's usage over the same period
airfry = from(bucket: "Systemstats")
  |> range(start: start, stop: stop)
  |> filter(fn: (r) => r._measurement == "power_watts" and r._field == "consumption")
  |> filter(fn: (r) => r.host == "air fryer")
  |> aggregateWindow(every: period, fn: mean)

// Union the tables so we can display a graph with 2 series
union(tables: [oven, airfry])

This gives us the following graph. It’s already fairly apparent which appliance is going to be responsible for most usage.

All subsequent statistics in this post are retrieved by appending to the union() statement in the query above.

Mean usage

If we look at the mean draw across the cook, we see that the oven’s average usage is significantly higher:

start = 2022-09-04T16:40:00Z 
stop = 2022-09-04T17:30:00Z 

...

// Union the tables so we can display a graph with 2 series
union(tables: [oven, airfry])
|> mean()
|> group()

Total usage

We know the average draw, but let’s look at the total power consumption for each appliance.

Calculating consumption from draw is fairly easy: If we draw n watts for an hour, then the usage is n Wh (with 1000 Wh being 1 kWh). If we draw n watts for 1/xth of an hour, then we need to divide n by x to have the calculated usage represent that fraction of time. For example:

A 30-second 3kW draw consumes (3000 / (60 * 2)): 25-watt hours.

Our data is windowed into 30-second periods (1/120th of an hour), so each window consumes 1/120th of the calculated usage.

So, to implement this, we add a simple conversion to the end of the query, taking the draw for that period and dividing it by 120:

// Union the tables so we can display a graph with 2 series
union(tables: [oven, airfry])
  |> map(fn: (r) => ({ r with
      // data is grouped into 30s windows, so if we're pulling 2kW 
      // in that window we're consuming
      //
      // usage / (mins-in-hour \* 2)
      // 2000 / 120
      //
      _value: r._value / 120.0
  }))
  // Calculate totals
  |> sum()
  |> group()

Giving the following results: The oven consumed more than double the energy demanded by the air fryer. Unsurprisingly, the proportions here are very similar to the proportion between the two appliance’s mean draw (the two figures being quite well correlated).

However, the oven did need to warm-up first. What happens if we only look at the time spent cooking (i.e., when food was in there)?

To do that, we adjust the start time at the head of the query so that the query starts after the oven has completed its warm-up:

start = 2022-09-04T16:59:00Z

The result is a large reduction in the reported consumption: The oven has a significant edge, managing to outperform the air fryer (which, even if it is able to do so while cooking, had to warm-up during that time).

Warmups

Of course, you may be thinking that this statistic isn’t particularly useful: you can’t reliably cook food without warming the oven.

However, the oven’s post-warm-up consumption is lower than that of the air fryer, which suggests that the oven might be able to outperform the air fryer when cooking over longer periods.

To understand the usage, we start by looking a little closer at the warmups:

• How long does warm-up take?
• What power is consumed during that time?
• What’s the consumption with that subtracted?

Because both devices have thermostatic control, we can easily tell when they reached temperature: there’s a corresponding drop in power consumption when the thermostat turns the heating element off.

You can see the warm-up periods highlighted in the graph below (red: oven, purple: air fryer). The warm-up timings were:

• Oven: (17:45 - 17:53) 8 minutes
• Air fryer: (18:08 - 18:15) 7 minutes

Of course, in practice, the oven didn’t cook anything for longer than 8 minutes because I wandered off to do other things and took a little too long to come back. Although that’s representative of real usage (or, certainly, representative of my usage), we won’t penalize the oven for my mistake when we do our calculations.

By changing the start and stop values on the query, we get consumption for each of the warm-up windows before taking the usage from the warm-up periods and subtracting them from each of the total usage figures:

| Device    | Warm Up Usage | Remaining Usage |
|---------------------------------------------|
| Oven      | 137 Wh        | 206 Wh          |
| Air fryer | 96.4 Wh       | 96.6 Wh         |
-----------------------------------------------

Although interestingly, they don’t tell us much on their own. We’ll use these figures later.

Heating element activity

One thing that stands out in the graph is how long the air fryer’s element stays active after the initial warm-up.

It’s a horrible visualization, but look at how much longer the air fryer element is active (the purple boxes) per instance than the oven (red boxes): The oven mainly has 30-second bursts (though there are a couple of 1-minute periods mixed in). Conversely, although the air fryer has a couple of 30s bursts, and there’s a 3- minute period where the element is constantly active.

This would seem to support the idea that the Oven is able to maintain temperature much more easily than the air fryer.

We can check how long the element in each device spent turned on:

**union**(tables: [oven, airfry])
  // Set a state to group by later
**|> map**(fn: (**r**) => ({r with
    state: **if** **r**._value > 1100 then
        "ON"
    else
      "OFF"
  }))

  // Calculate the total stateduration
**|> elapsed**(unit: 1s)
**|> filter**(fn: (**r**) => **r**.state == "ON")
**|> sum**(column: "elapsed")
**|> group**()

By changing the start and end times, we can see how long the element was active during each cooking stage.

| Device    | Total   | After Oven Warmup | After Air Fryer Warmup |
|------------------------------------------------------------------|
| Oven      | 22 mins | 14 Mins           | 1 Minute               |
| air fryer | 12 mins | 12 Mins           | 6 Minutes              |
--------------------------------------------------------------------

50% of the air fryer’s activity occurred after warmup, while 63% of the oven’s heating time occurred post-warmup.

But the oven was also on for longer (making its post-warmup time disproportionately larger than the air fryers), so we need to make the comparison proportional by taking the total cook time into account:

| Device    | Cook Time (exc warmup) | Element Time (exc warmup) | Element Time |
|-------------------------------------------------------------------------------|
| Oven      | 32 Mins                | 14 Mins                   | 43.75%       |
| air fryer | 10 Mins                | 6 Mins                    | 60.00%       |
---------------------------------------------------------------------------------

The air fryer spent significantly more of its non-warmup time with the element sucking power. So, it’s certainly possible that the oven could prove to be more energy-efficient after a period.

Can the oven be more efficient?

We can work out roughly where the break-even falls. If we reduce the post-warmup average consumption to a per-minute average, we can compare them to predict how many minutes of cooking time it would take for the oven to outperform the air fryer.

We collected the figures we need above:

| Device    | Cook Time (exc warmup) | Power Consumed (exc warmup) | Power consumed (Warmup) |
|--------------------------------------------------------------------------------------------|
| Oven      | 32 Mins                | 206 Wh                      | 137 Wh                  |
| air fryer | 10 Mins                | 96.6 Wh                     | 96.6 Wh                 |
----------------------------------------------------------------------------------------------

To calculate the average Wh consumed per minute, we do:

Consumed / time = average minutely consumption Giving the following figures:

• Oven: 206 Wh / 32 mins = 6.4375 Wh/min
• Air fryer: 96.6 Wh / 10 mins = 9.66 Wh/min

The oven is significantly more efficient per minute.

But before that efficiency advantage can translate into an overall energy saving, the oven must cancel out the additional energy it consumed during its warmup period.

To calculate when it’ll reach that point, we calculate the difference in warmup consumption and divide it by the difference in per-minute consumption.

    137 - 96.6 = 40.4 Wh
-------------------------------   = 12.54 minutes
   9.66 - 6.4375 = 3.2225 Wh

So, all things being equal, the oven would break even after ~13 minutes.

But not all is equal: The air fryer also requires less cooking time (10 minutes less for chips), so the oven consumes an extra 10 minutes of energy.

Adding this into our calculation moves the break-even point quite considerably:

    (137 - 96.6)
  + (10 * 6.4375) = 104.757 Wh
--------------------------------   = 32.51 minutes
   9.66 - 6.4375 = 3.2225 Wh

At nearly 33 minutes, this is more than double the time the air fryer requires to cook the chips.

Spuds

Fifteen minutes is quite a short cooking time, though—do these results hold for something that requires longer?

If we take the timings from two baked potato recipes (oven and air fryer), we should be able to work out which is more energy-efficient:

• Oven potatoes require 75-90 mins (we’ll split the difference and call it 83).
• Fryer potatoes require 50 mins.

The oven potatoes need 33 mins more, so assuming that warmup and per-min consumption doesn’t change:

    (137 - 96.6) 
  + (33 * 6.4375) = 252.84 Wh
--------------------------------   = 78 minutes
   9.66 - 6.4375 = 3.2225 Wh

The break-even is at 78 minutes, which (again) is longer than the air fryer needs.

Technically, the break-even will be even further out than that because the oven recipe requires a higher temperature than our chips, so the warm-up and maintenance consumption would be higher.

To summarize, an oven uses less energy per minute post-warmup than an air fryer, but because it needs substantially less time to cook food, it still uses less energy overall.

Purchase break-even

Given the energy crisis looming in the UK, it’d be remiss not to also examine the financial side of this.

If you’re reading this, it’s possible you haven’t yet bought an air fryer and are considering doing so to reduce your energy bills. Since you probably already have an oven, the upfront cost comparison is £0 vs. $airfryer_cost.

To determine whether it’s worth buying an air fryer, we need to consider how long it will take for the energy savings to break even with the purchase cost (known as amortization).

If we consider the following:

• The air fryer I tested costs £72.99 (although you can get an Air Fryer for around £40).
• Including warm-ups (let’s be realistic, you’re never going to consistently leap on the oven as soon as it’s warmed up), the air fryer consumed 150 Wh less than the oven when cooking chips.
• In October, the cost of electricity will (for many) rise to £0.52/kWh

We can conclude that:

• The air fryer saved (52/1000 * 150) £0.078 in energy when cooking my chips
• At £0.078 per cook, break-even would happen after (72.99 / 0.078) 936 similar cooks

At one cook a day, the energy savings would take two and a half years to offset the £72.99 purchase price. Assuming a £40.00 air fryer can deliver the same energy savings, it would still take nearly 18 months to break even.

To put that into perspective:

• If I cook chips once daily for 31 days, I would reduce my energy bills by just 4.65 kWh / £2.41 a month.
• If I spread the cost of the air fryer, interest-free, over 18 months, I would pay £4.05/month
• Despite the energy saving, I’d therefore lose £1.64 a month

It’s (hopefully) unlikely that you’re going to be living off chips alone, so let’s also project usage for baked potatoes:

     Oven: 137 + (83 * 6.4375) = 671.31 Wh
  -  air fryer: 96.6 + (50 * 9.66) = 579.6 Wh
    -------------------------------------------
                  91.71 Wh

The saving on baked potatoes is actually lower, and saves (52/1000 * 91.71) £0.0477 per cook (giving a 4 year amortization period).

This means that, even if you manage to find an air fryer at half the price I paid, the break-even is still years away.

Conclusion

Despite needing to achieve a higher temperature, the air fryer used significantly less power cooking my chips.

The fact that it doesn’t need to be warmed up first contributes quite significantly to this: not just because it’s not spending time heating rather than cooking, but also because it removes the opportunity for a human to get side-tracked and forget to put the food in (guilty, your honor).

The oven consumes significantly less energy maintaining temperature than the air fryer (likely because of better insulation). However, the air fryer’s faster cooking time mitigates this, lowering overall energy consumption.

So, to answer our questions:

Is an air fryer more energy efficient than an oven?

Yes, but only if you use it properly and adjust cooking times.

If you air-fry food for the same time as you would in an oven, it may take as little as 13 minutes for the oven to become the less expensive option (and your food will probably be horribly burnt).

When will I break even?

Even at the insane prices we’re all going to be paying, the savings per meal are very small. It’ll likely take years for the energy savings to break even with the up-front cost of purchasing an air fryer. In some cases, it may take longer than the useful life of the air fryer.

Should I invest in an air fryer to avoid high energy prices?

The long amortization period means that if you’re concerned about how you will afford energy bills this winter, purchasing an air fryer isn’t a good way to address it. The air fryer will reduce your energy consumption, but only very slightly, and the up-front purchase cost will make you worse off overall.

Unless you can find a deeply discounted air fryer (or be gifted one, or pay off the loan interest-free over an extremely extended period), it’s unlikely to be the right decision from a purely financial point of view.

Obviously, if you already have an air fryer, then you incurred the capital cost, so using it where you can will slightly reduce your energy bill, with each saving bringing the break-even point slightly closer. And they do make some very nice chips.

To start monitoring the energy of your appliances, sign up for a free cloud account now. To add InfluxDB to larger projects, contact our sales team for a custom POC.

Update: cooking at 180

After I published this post, a Twitter user raised an interesting point. The oven’s manual doesn’t provide any guidance, but I could have tried cooking in both at 180c, demanding lower consumption from the air fryer and increasing its overall advantage. I expected that it wouldn’t make much material difference to the conclusion of this post, but I thought I’d give it a try nonetheless.

This evening, I cooked some chips using the following:

• Temperature: 180c
• Time: 15 minutes (as before)

The chips came out cooked, but, honestly, they weren’t that great—they hadn’t crisped very much and had that unpleasant wet oven-cook feel to them. They either needed longer or the manual’s recommended temperature. But what we’re interested in is the power consumption.

I graphed consumption using the same query as before:

period = 30s
from(bucket: "Systemstats")
  |> range(start: 2022-09-24T16:45:00Z, stop: 2022-09-24T17:05:00Z)
  |> filter(fn: (r) => r._measurement == "power_watts" and r._field == "consumption")
  |> filter(fn: (r) => r.host == "air-fryer")
  |> aggregateWindow(every: period, fn: mean)

Giving the following graph: Using the same queries as in the earlier part of this post, we can see that the total consumption for this cook was 174 Wh, just 19 Wh less than the cook at 200 Celsius. So it saved 169 Wh when compared to the oven cook.

If we re-run the break-even calculations using this figure, we can see that

• At 180c it saves (52/1000 * 169) £0.088 in energy.
• At £0.088 per cook, break even will take (72.99 / 0.088) 829 similar cooks.
• At one cook a day, break-even is around two years, 3 months, and 8 days.
• A £40 fryer achieving the same savings would take 1 year, 2 months, and 27 days to break even.
• 31 days of chips once a day would reduce energy bills by just 5.24 kWh / £2.72.
• Assuming interest-free repayment of the purchase at £4.05/month, we’d be £1.33 worse off a month.

There’s also the issue of the quality of the chips we get. Realistically, you’re only likely to eat them like that once, and then on subsequent cooks, you’ll either increase the temperature (back to 200) or the time.

So, let’s work out the impact of adding time. W. We’re interested in the average power usage while the air fryer maintains temperature (the bulk of energy usage is in the initial warm-up).

The graph shows that the warm-up finished at 17:53:30, the cook finished at 18:02:30, and the maintenance period was 9 minutes.

During that time it consumed 76.6 Wh, so the average consumption per minute was (76.6/9) 8.5Wh.

Assuming the chips required an additional 5 minutes (in practice, that’s probably still not enough), we’d likely consume another 42.5 Wh. The advantage gained by dropping to 180c was only 19 Wh, so we’re now worse off by around 23.5 Wh (although still ahead of the oven).

So, although cooking at 180c does reduce the energy consumption a little

• It doesn’t make a material difference to the conclusion: it’s still a poor solution to energy prices unless you already own one
• You’ll save around £0.009 versus cooking at 200c
• The chips you get from those cooks won’t be nearly as good as those done at 200c.
• Adjusting the cook time to account for the lower temperature results in higher energy usage than the shorter, high-temperature cook

One additional concern I’ve developed since originally writing the post is realistic usage patterns.

The air fryer will save you a little money if you use it instead of the oven. However, because it makes such good chips, it’s easy to slip into the habit of using it as well as the oven, increasing your overall power consumption. Having a dual-zone air fryer can help with this a little, but it becomes quite hard to put chips in the oven knowing how much better they’ll be from the fryer.