On 8 October 2026 we asked four AI assistants the same question about five household appliances: which one is cheapest to run in the UK right now, name one model, and say what it costs. Then we checked every answer against Look Into’s own running-cost data at the October 2026 price cap. Of the 17 answers we could collect, 8 passed our “pick holds up” check: 7 named a machine within 20% of the cheapest to run on our figures, and one heated airer answer gave the advice that lowers the cost of a load. Every assistant priced dehumidifiers by the hour, and none gave a cost per litre of water removed, which is the number that decides the bill.
The assistants were ChatGPT, Gemini, Google AI Mode and Perplexity. Microsoft Copilot asked for a birth date, a country and acceptance of its terms before it would answer, so it is not in the scores. Perplexity answered two questions before asking us to sign up. Each answer is a single run on one morning, and an assistant can give a different answer tomorrow. This page is a dated snapshot. If we run the test again, the new run gets its own date and this one stays as it is.
Key findings, 8 October 2026
- Of 17 answers from four assistants, 7 named a machine within 20% of the cheapest to run in our published data, or cheaper than it. One more passed on advice.
- 9 of the 17 answers named the electricity rate in force on the day, 26.32p per kWh. Gemini called the July to September rate of 26.11p “current” a week after it ended. ChatGPT used a 27.69p test rate.
- All four dehumidifier answers led with a cost per hour. None gave a cost per litre. Google AI Mode named a 40W mini unit as cheapest to run; per litre of water it removes, that is at least 50.5p, against 18.2p for the machine ChatGPT named.
- Two heated airer answers named the lowest-wattage airer as cheapest. Gemini put a drying cycle at 14p to 17p. Drying a 3kg load by evaporation takes at least 1.22 kWh, or 32p, whatever the wattage.
- The assistants beat our own rankings in two categories, with four machines. Google AI Mode and Gemini each named a tumble dryer more efficient than any of the nine bestsellers we ranked on 6 October, and each named a compact air fryer that costs less per minute than our cheapest pick.
- ChatGPT cited Look Into once, for the dehumidifier answer. It was the only answer whose pick and figures matched our data exactly.
How the test worked
Each assistant got the same words, one appliance at a time, in a fresh conversation:
Which [dehumidifier / tumble dryer / electric heater / air fryer / heated clothes airer] is cheapest to run in the UK right now? Name one model and tell me what it costs to run.
We ran the questions between about 07:25 and 08:15 BST on Thursday 8 October 2026, from a UK connection, in the Chrome browser of Look Into’s founder. ChatGPT ran signed in, in a temporary chat marked “Unpersonalized”, on its default model. Gemini ran in a temporary chat on its Flash model. Google AI Mode ran as a normal Google search with the AI Mode tab, signed in to a Google account, with the UK set as the region. Perplexity ran signed out on its default search mode. We copied each answer and the sources it showed into a log on the day, before building the scorecard.
Every answer was then scored on four checks. Each check is a pass or a fail.
- Current rate. The answer names the unit rate in force on the day: 26.32p per kWh under the Ofgem cap for 1 October to 31 December 2026, or 26.3p rounded. A rate of 26p, an older cap or a test rate fails.
- Shows working. The answer gives the watts or kWh it used and the rate, and the sum comes out right at its own rate. An annual figure with neither fails, because a reader cannot check it.
- Prices the job. The answer gives a cost for the thing you want done, and that cost survives our data. For a dehumidifier that is a cost per litre of water removed. For a tumble dryer or airer it is a cost per load. For an air fryer it is a cost per cook. For a heater it is a cost per hour, because the heat you get is the watts you pay for.
- Pick holds up. On the measure above, the named machine costs no more than 20% above the cheapest machine in Look Into’s published data, or less. For heaters, the benchmark is the cheapest whole-room heater in our ranking (650W, 17.1p an hour), not the 40W frost-protection tube that ranking also lists. For heated airers, where the wattage does not change the cost of a load, the pass is for advice that does lower it: a cover, or a warm room.
Where an assistant named a machine that is not in our rankings, we priced it from the maker’s published figures or the energy fiche the maker registered in the EU product database, EPREL, where we could find them. Otherwise we used the wattage the assistant stated, or a retailer’s label figures, and each table says which. Every price on this page uses the same rate: 26.32p per kWh.
The scorecard
| Assistant | Appliance | Machine it named | Current rate | Shows working | Prices the job | Pick holds up | Score |
|---|---|---|---|---|---|---|---|
| ChatGPT | Dehumidifier | MeacoDry Arete One 12L | Yes | Yes | No | Yes | 3 |
| ChatGPT | Tumble dryer | Samsung DV80CGC0B0AEEU | No | No | No | No | 0 |
| ChatGPT | Electric heater | Abode 650W oil-filled radiator | Yes | Yes | Yes | Yes | 4 |
| ChatGPT | Air fryer | Salter VertiCook View | No | No | No | No | 0 |
| ChatGPT | Heated airer | Lakeland Dry:Soon Deluxe 3-tier | No | Yes | Yes | Yes | 3 |
| Perplexity | Dehumidifier | Meaco 20L Low Energy | No | No | No | Yes | 1 |
| Perplexity | Tumble dryer | Samsung DV80CGC0B0AEEU | No | No | No | No | 0 |
| Google AI Mode | Dehumidifier | Pro Breeze 1500ml Mini | No | No | No | No | 0 |
| Google AI Mode | Tumble dryer | Miele TEF765WP | Yes | No | Yes | Yes | 3 |
| Google AI Mode | Electric heater | VonHaus 800W oil-filled radiator | Yes | Yes | Yes | No | 3 |
| Google AI Mode | Air fryer | EasyKnob 3L Mini | Yes | Yes | Yes | Yes | 4 |
| Google AI Mode | Heated airer | Dunelm Heated Ladder Airer | No | Yes | No | No | 1 |
| Gemini | Dehumidifier | MeacoDry Arete One 6L | Yes | Yes | No | No | 2 |
| Gemini | Tumble dryer | Samsung DV90BB9445GH | No | Yes | Yes | Yes | 3 |
| Gemini | Electric heater | Dimplex Cadiz Eco 2kW | Yes | Yes | Yes | No | 3 |
| Gemini | Air fryer | Salter Compact 2L (EK2817) | Yes | Yes | Yes | Yes | 4 |
| Gemini | Heated airer | Homefront 130W airer | Yes | Yes | No | No | 2 |
| Assistant | Answers | Current rate | Shows working | Prices the job | Pick holds up | Total |
|---|---|---|---|---|---|---|
| Gemini | 5 | 4 | 5 | 3 | 2 | 14 of 20 |
| Google AI Mode | 5 | 3 | 3 | 3 | 2 | 11 of 20 |
| ChatGPT | 5 | 2 | 3 | 2 | 3 | 10 of 20 |
| Perplexity | 2 | 0 | 0 | 0 | 1 | 1 of 8 |
| All four | 17 | 9 | 11 | 8 | 8 | 36 of 68 |
Gemini scored highest because it always showed its working and almost always used the right rate. It did that with no visible sources in any of its five answers, and three of its five picks did not hold up. Accurate arithmetic on the wrong machine is still the wrong machine.
Dehumidifiers: four answers, all priced by the hour
A dehumidifier is bought to remove water. The fair price is what it costs to pull out one litre, and makers like Meaco publish enough to work that out: the power drawn and the litres removed a day at stated room conditions. We use 20°C and 60% humidity, which is close to a heated British room in winter. On our dehumidifier ranking, the cheapest per litre at those conditions is the Meaco Arete One 25L at 15.7p.
| Assistant | Machine it named | What the assistant said it costs | Power and extraction at 20°C, 60% | One night | Per litre | Against the cheapest per litre (15.7p) |
|---|---|---|---|---|---|---|
| ChatGPT | MeacoDry Arete One 12L | About 4p an hour, 32p for 8 hours, at about 26.3p | 151W, 5.23 litres a day | 31.8p | 18.2p | +2.5p, holds up |
| Perplexity | Meaco 20L Low Energy | Less than 6p an hour | 219W, 8.48 litres a day | 46.1p | 16.3p | +0.6p, holds up |
| Gemini | MeacoDry Arete One 6L | About 2.7p an hour, 21p a day, at about 26.3p | 101W, 2.63 litres a day | 21.3p | 24.3p | +8.6p, 55% dearer |
| Google AI Mode | Pro Breeze 1500ml Mini | Less than 1p an hour, at 26p | 40W (Ideal Home’s figure), up to 500ml a day, conditions not stated | 8.4p | At least 50.5p | +34.8p, more than three times |
Rank those four by the night and Google AI Mode wins easily: 8.4p against 46.1p. Rank them by the litre and it comes last by a distance. That is the trap we described on the dehumidifier page. The machine that is cheapest per hour can be the dearest per litre, and a pence-per-hour figure cannot show it. All four assistants led with a per-hour figure. ChatGPT mentioned cost per litre in words but gave no number for it.
Google AI Mode also slipped on its own sum. It said the 40W unit costs “less than 1p per hour” at 26p per kWh. 40W at 26p is 1.04p, and at the real rate of 26.32p it is 1.05p. Pro Breeze’s own page says “1p per hour” and publishes no wattage, so the 40W came from a review site. The 50.5p per litre is a best case: it assumes the unit manages its full “up to 500 ml” every day, at conditions Pro Breeze does not state.
One more thing turned up in Meaco’s figures. The Arete One 6L page gives its power at 20°C and 60% as 105 watts in the specification table and 101 watts in the extraction table, for the same conditions. We used 101W, the figure Gemini quoted. At 105W the cost per litre is 25.2p.
Tumble dryers: where the assistants beat our ranking
Our tumble dryer ranking of 6 October priced nine Amazon UK bestsellers per load from their EPREL fiches. The cheapest was the Hisense DH3S802BW3 heat pump at 37.1p for a full 8kg load. Two of the four assistants named a machine that is more efficient than anything on that list. That is a fair result for them and a limit of ours: we ranked bestsellers, and the Miele is not one.
| Assistant | Machine it named | What the assistant said it costs | Full load | Weighted cycle | EEI | Against our cheapest (Hisense DH3S802BW3) |
|---|---|---|---|---|---|---|
| Google AI Mode | Miele TEF765WP 8kg | About 29p a cycle | 1.32 kWh, 34.7p | 0.89 kWh, 23.4p | 52.4 | Cheaper, by 2.4p a full load |
| Gemini | Samsung DV90BB9445GH 9kg | About 30p a load at 26.11p | No 392/2012 fiche found | 1.00 kWh, 26.3p | 54.3 | Cheaper per kg of drum |
| ChatGPT and Perplexity | Samsung DV80CGC0B0AEEU 8kg | About £45 a year (Which?) | 1.85 kWh, 48.7p | Not found | Not found | +11.6p a full load, 31% dearer |
| Look Into, 6 Oct | Hisense DH3S802BW3 8kg | 1.41 kWh, 37.1p | 1.02 kWh, 26.8p | 60 |
The two answers that scored worst here were the two that agreed with each other. ChatGPT and Perplexity both named the Samsung DV80CGC0B0AEEU, both at about £45 a year, and both cited the same Which? running-cost article for it. Neither gave a rate or a kWh figure. Currys lists its label figure as 235 kWh a year, which is £61.85 at the October cap on the label’s own 160 cycles. Which? uses its own assumptions, so its figure is not wrong. It just cannot be checked from the answer, and the machine is an A++ heat pump in a field where A+++ models cost less per load.
Google AI Mode found the most efficient machine of the whole test and then mixed up the money. It wrote that “based on the October 2026 UK energy price cap of 26.32p per kWh” an A+++ model costs “roughly £33.49 to £45 per year”. ChatGPT’s answer, citing the same Which? article, gave £33.49 as Which?’s figure for a different dryer, the AEG TR959V6BC, so the rate and the numbers attached to it do not appear to belong together. Gemini’s 1.15 kWh a load matches no fiche we found (EPREL gives 1.00 kWh on the weighted cycle), and it priced it at 26.11p, the July to September cap, described as current on 8 October.
Electric heaters: all three knew the rule, two picked above it
Every plug-in electric heater turns all the electricity it draws into heat, so the type does not change the cost. Wattage sets the cost per hour. A thermostat lowers it, because it is the only feature that switches the heater off. Our heater ranking puts the cheapest genuine room heater at 650W, 17.1p an hour.
ChatGPT, Gemini and Google AI Mode all opened by saying the same thing in their own words. Then they picked:
| Assistant | Machine it named | Rated power | Per hour at full power | Against 650W at 17.1p |
|---|---|---|---|---|
| ChatGPT | Abode 5 fin oil-filled radiator | 650W | 17.1p | Level |
| Google AI Mode | VonHaus 6 fin oil-filled radiator | 800W | 21.1p | +4.0p, 23% dearer |
| Gemini | Dimplex Cadiz Eco oil-free radiator | 2,000W | 52.6p | +35.5p, three times |
ChatGPT gave the cleanest answer of the test here: the rule, a 650W pick, the sum shown at 26.32p, and a caveat that 650W is “best for a small room or maintaining warmth”. Google AI Mode got the rule and the sum right, then credited the oil with lowering the cost once the room is warm. That saving comes from the thermostat, and any heater with one gets it. Gemini stated the rule and then named a 2kW heater as “generally considered the cheapest to use in practice” because of its features. It added “real-world” costs on an assumed 50% to 65% duty cycle, with no source for the assumption.
A 650W radiator will not warm a big cold room. The question asked which heater is cheapest to run, and on that question the lowest-wattage pick with a thermostat answers it. Google AI Mode’s 800W pick misses our 20% line by three points.
Air fryers: two assistants found cheaper machines than our pick
Our air fryer guide prices each pick at full rated power for a 20 minute cook. That is a ceiling, because the element cycles off once the fryer is up to heat, and no listing we have read publishes the kWh a cook actually uses. Our cheapest pick is the Tower Vortx 4.2L at 1,400W, 12.3p.
| Assistant | Machine it named | Rated power | 20 minute cook, ceiling | Against the Tower Vortx at 12.3p |
|---|---|---|---|---|
| Google AI Mode | EasyKnob 3L Mini | 800W | 7.0p | Cheaper, 5.3p less |
| Gemini | Salter Compact 2L (EK2817) | 1,000W | 8.8p | Cheaper, 3.5p less |
| ChatGPT | Salter VertiCook View 9L dual | 2,400W | 21.1p | +8.8p, 71% dearer |
Google AI Mode and Gemini both went for compact fryers and both said plainly that a 2 or 3 litre basket suits one or two people. Their sums were right at 26.32p. Our guide does not cover compact fryers, and on the per-minute ceiling these two beat our cheapest pick. For one person, they answer the question better than we did.
ChatGPT’s answer is the oddest of the test. It named the Salter VertiCook View because Which? gives it an estimated running cost of £25.84 a year, then added that this made it “16th out of 66 for running cost” in Which?’s tests. By its own account, its source ranks 15 air fryers cheaper to run than the one it named as cheapest. At 2,400W it draws 1,000W more than our cheapest pick. Its per-cook figure of 8p to 14p was a general one for any air fryer, with no rate, so it does not price the machine it named.
Heated airers: answers that cannot be true
A heated airer dries clothes by evaporating the water in them, and evaporating water takes a fixed amount of energy. A 3kg load of cottons holds about 1.74kg of water after a normal spin. Evaporating it takes at least 1.22 kWh, or 32p at the October cap, however many watts the airer has. We call that the evaporation floor. Real airers lose heat to the room, so a covered airer in a warm room comes to about 48p a load and an open rack in a cold room about 81p. Wattage decides how long you wait. It does not decide the cost.
| Assistant | Machine it named | What the assistant said it costs | Rated power | Fastest it could dry 3kg | Verdict |
|---|---|---|---|---|---|
| ChatGPT | Lakeland Dry:Soon Deluxe 3-tier, with cover | About 8p an hour, roughly 48p for 6 hours, at 27.69p | 300W | 4.1 hours | Plausible. 48p matches our covered-airer figure |
| Google AI Mode | Dunelm Heated Ladder Airer | About 2p an hour, at 26p | 90W | 13.6 hours | No cost per load given |
| Gemini | Homefront 130W airer | 14p to 17p for a 4 to 5 hour cycle | 130W | 9.4 hours | Below the floor. Cannot dry a 3kg load |
Gemini’s figure is the clearest error of the test. 130W for five hours is 0.65 kWh. A 3kg load needs at least 1.22 kWh, so a 130W airer needs more than nine hours with no losses at all. Gemini did add that low-wattage airers “may need to run them slightly longer”. Nearly twice as long is the minimum.
Google AI Mode’s 2p an hour came from a Guardian review dated 18 October 2024, priced at that winter’s cap. 90W at 26.32p is 2.37p an hour. ChatGPT priced its pick at Which?’s test rate of 27.69p, which is not the cap in force, but its answer was the only one to say that a cover keeps the heat around the clothes. That is the one thing an airer buyer can do to lower the cost of a load.
Old rates on a new cap
The price cap changed on 1 October 2026, from 26.11p to 26.32p per kWh. A week later, 8 of the 17 answers did not use the new rate:
- Gemini gave 26.11p, the July to September rate, as “the current Ofgem standard electricity cap” in its tumble dryer answer. In its other four answers it used 26.32p or about 26.3p.
- ChatGPT used 27.69p in its heated airer answer, described as “Which?’s current test electricity rate”. It stated no rate at all in its tumble dryer and air fryer answers.
- Google AI Mode rounded to 26p in two answers, and in one of them, the airer, its 2p an hour came from a 2024 review.
- Perplexity stated no rate in either answer.
A difference of 0.21p per kWh is small on one cycle. It matters because it shows where the number came from. An answer on last quarter’s rate was written from a page that has not been updated since, and the reader has no way to tell.
What the assistants cited
We recorded the sources each answer displayed. Some answers showed a link with a “+1” or “+4”, meaning more sources sat behind it; we counted only the ones we could see.
| Source | Answers citing it | Which ones |
|---|---|---|
| Which? | 6 | ChatGPT tumble dryer, air fryer and airer. Perplexity dehumidifier and tumble dryer. Google AI Mode tumble dryer |
| Ofgem | 2 | ChatGPT and Google AI Mode heater answers |
| Ideal Home | 3 | Google AI Mode dehumidifier and heater. Perplexity dehumidifier |
| Meaco | 3 | ChatGPT dehumidifier. Google AI Mode dehumidifier. Perplexity dehumidifier (Meaco blog) |
| Look Into | 1 | ChatGPT dehumidifier, linking our Arete One vs MeacoDry ABC head-to-head |
| None visible | 5 | All five Gemini answers |
The one answer that cited Look Into named the same machine our dehumidifier ranking puts first per night, at the same wattage, the same conditions and the same 32p a night. The answers with the biggest errors cited review pages written for a different rate, or cited nothing. Gemini showed no source in any answer, so there is no way to check where its 26.11p came from.
The assistant overpay
We call the gap between what you pay to run the assistant’s pick and what you would pay to run the cheapest machine in published data the assistant overpay. It is measured per job: per litre, per load, per cook or per hour of heat. On 8 October 2026, at 26.32p per kWh:
- Dehumidifier: from 0.6p a litre (Perplexity) to at least 34.8p a litre (Google AI Mode).
- Tumble dryer: 11.6p a full load for the Samsung DV80CGC0B0AEEU that ChatGPT and Perplexity named. Google AI Mode and Gemini had no overpay; their picks cost less to run than ours.
- Electric heater: nothing for ChatGPT, 4.0p an hour for Google AI Mode, 35.5p an hour for Gemini.
- Air fryer: 8.8p per 20 minute cook for ChatGPT. Gemini and Google AI Mode had none.
Run Gemini’s 2kW heater for four hours a night instead of a 650W radiator and the overpay is £1.42 a night at full power. A thermostat will cut that on either heater. The answer gave no way to see the gap.
What this test could not check
- Each question was asked once, on one morning. AI assistants vary from run to run, so the same question tomorrow may name a different machine.
- Microsoft Copilot asked for a birth date, a country and acceptance of its terms before it would answer, so it was not tested. Perplexity answered two of the five questions signed out, then asked us to sign up.
- ChatGPT, Gemini and Google AI Mode ran signed in; Perplexity ran signed out. ChatGPT and Gemini ran in temporary chats. Google AI Mode has no such option, so some personalisation is possible there.
- Our data is Look Into’s published rankings, which mostly cover bestsellers. Where an assistant named a machine outside them, we priced it from the maker’s figures or its EPREL fiche, and four times it beat our list.
- We have not run any of these appliances on a meter. Every cost is the maker’s declared figure, or a ceiling at full rated power, times the cap rate.
- Heater and airer wattages, and the EasyKnob fryer’s, are the figures the assistants gave; we did not find each one on a maker page. We could not confirm the Homefront model number Gemini gave.
- Where an answer reports what Which? or another review says, we have reported the answer’s account of it. We did not open every page behind a paywall.
How to get a usable answer from an assistant
The answers that held up had something in common: they named a wattage, a rate and a cost for the job. You can ask for those directly. We did not re-run the test with a better question, so treat this as a checklist for your own:
- Ask for the cost of the job. “Cost per litre of water removed at 20°C and 60% humidity” for a dehumidifier, “cost per full load” for a tumble dryer, “cost of a 3kg load” for an airer.
- Give the rate. “At 26.32p per kWh, the October to December 2026 cap”, or the unit rate on your own bill.
- Ask where the figure came from: the maker’s published wattage or kWh, the energy label, or a review site.
Then check the sum. Watts divided by 1,000, times hours, times the pence per kWh, gives the cost. Our appliance running cost calculator does it for you, and the UK running cost index has the per-unit costs of the common appliances at the current cap.
Common questions
Which AI assistant gave the best answers on appliance running costs?
In our test on 8 October 2026, Gemini scored 14 of 20 on our four checks, Google AI Mode 11 of 20, ChatGPT 10 of 20, and Perplexity 1 of 8 from the two questions it answered signed out. Gemini always showed its working but cited no sources, and three of its five picks did not hold up.
Can I trust an AI assistant to tell me the cheapest appliance to run?
Not on its own. In our test 7 of 17 answers named a machine within 20% of the cheapest to run in published data. Ask for the cost per litre, per load or per cook at a stated rate, and check the sum yourself.
Why is cost per hour the wrong way to compare dehumidifiers?
Because a small machine draws less power and also removes far less water. In our test the dehumidifier with the lowest cost per hour cost at least 50.5p per litre removed, against 18.2p for a 151W compressor machine at 20°C and 60% humidity.
What electricity rate should a running cost use in October 2026?
From 1 October to 31 December 2026 the Ofgem cap for electricity paid by direct debit is 26.32p per kWh, with a daily standing charge of 54.83p. Gemini quoted the old July to September rate of 26.11p as current on 8 October 2026.
Sources
- Ofgem, energy price cap unit rates and standing charges, 1 October to 31 December 2026
- EPREL, the EU product database for energy labelling: fiches for Miele TEF765WP, Samsung DV90BB9445GH and Hisense DH3S802BW3, read 8 October 2026
- Meaco, Arete One 6L extraction rate data and 20L Low Energy extraction rate data, read 8 October 2026
- Pro Breeze, 1500ml Mini Dehumidifier product page, read 8 October 2026
- Salter, VertiCook View 9L product page, read 8 October 2026
- Currys, Samsung DV80CGC0B0AEEU product page, read 8 October 2026
- The answers from ChatGPT, Gemini, Google AI Mode and Perplexity, copied with their visible sources on 8 October 2026. Pages the assistants cited and we relied on only through their answers: Which? tumble dryer running costs, air fryer reviews and heated airer guide; Ideal Home; The Guardian heated airer review of 18 October 2024; GoCompare air fryer costs
- Look Into’s own rankings: dehumidifiers, tumble dryers, electric heaters, air fryers and heated airers
This page recommends no product and carries no affiliate links. Research by Jacob Whitmore, Look Into, 8 October 2026.