MacBook Air M5 (13-inch) vs MacBook Air M5 (15-inch), 16GB for local AI
The MacBook Air M5 (13-inch), 16GB and the MacBook Air M5 (15-inch), 16GB are the same machine inside: 10-core CPU / 10-core GPU, 16 GB of memory at 153 GB/s. Both hold 10 of the 39 open models here. The MacBook Air M5 (13-inch), 16GB costs $200 less. On Gemma 4 12B, the strongest model both hold, they run at much the same speed: 14 and 14 tok/s, both estimated from memory bandwidth. The MacBook Air M5 (13-inch), 16GB pays for itself sooner, in 102 years against 118 years at 500k tokens a day.
| MacBook Air M5 (13-inch), 16GB | MacBook Air M5 (15-inch), 16GB | |
|---|---|---|
| Price | $1,299 | $1,499 |
| Memory | 16 GB | 16 GB |
| Usable by the GPU | 10.5 GB | 10.5 GB |
| Memory bandwidth | 153 GB/s | 153 GB/s |
| Power under load | 65 Wstand-in | 65 Wstand-in |
| Models that fit | 10 | 10 |
| Best model it runs | Gemma 4 12B | Gemma 4 12B |
| Speed on that model | 14 tok/s estimated | 14 tok/s estimated |
| Pay-back on that model | Pays back in 102 years | Pays back in 118 years |
Run the numbers on the MacBook Air M5 (13-inch), 16GB · or the MacBook Air M5 (15-inch), 16GB
The same machine inside
Both have the same 10-core CPU / 10-core GPU, the same 16 GB of memory and the same 153 GB/s to read it at, and both leave 10.5 GB of that memory to the GPU. What a machine holds is decided by that last figure, so they hold the same 10 models, and not only at 32k of context: across all 39 models the calculator counts, at every context from 4k to 256k, there is no model one holds and the other does not. They run those models at the same speed too: decoding reads the weights out of memory, and both read them at 153 GB/s.
So the whole question on this page is the $200 between them. The MacBook Air M5 (15-inch), 16GB costs that much more than the MacBook Air M5 (13-inch), 16GB for the same models at the same speed, and every difference in pay-back on this page comes from that and nothing else. The power row is not two measurements: both figures are stand-ins borrowed from the nearest hardware the data has, so the two matching is a fact about the data rather than about the machines. This page still prices the electricity into both from those numbers. What else separates them is not something this site measures: it prices what a machine holds, how fast it runs it and what it draws, and everything from the case to the ports to the warranty is yours to weigh against the $200.
How much use it takes to pay back
Everything above is at 500k tokens a day. Pay-back moves with how much you actually run, so here are both machines on Gemma 4 12B, the strongest model both hold, at the five levels of use the calculator names. The MacBook Air M5 (13-inch), 16GB pays back sooner at every level of use, so this is not a choice that turns on how hard you work it.
| A day's use | MacBook Air M5 (13-inch), 16GB | MacBook Air M5 (15-inch), 16GB |
|---|---|---|
| 50ka few chats a day | 1,020 years | 1,177 years |
| 200klight assistant use | 255 years | 294 years |
| 1Ma moderate coding-assistant day | 51 years | 59 years |
| 4Mheavy coding with an agent | 13 years | 15 years |
| 20Magents running most of the day | 2.6 yearsits ceiling | 3.0 yearsits ceiling |
On Gemma 4 12B neither machine can generate 20M tokens a day: the MacBook Air M5 (13-inch), 16GB manages at most 19.8M and the MacBook Air M5 (15-inch), 16GB at most 19.8M. Both figures on that row are for the most each can do.
Run the MacBook Air M5 (13-inch), 16GB at 20M tokens a day · or the MacBook Air M5 (15-inch), 16GB
The assumptions behind both columns
Both columns use the same usage: 500k tokens a day at 15:1 input to output, 32k of context, $0.17 per kWh, and today's API prices held flat. Speeds marked estimated are worked out from memory bandwidth rather than measured, and pay-back scales with them. Graphics cards are priced as the card alone, so add the PC around one before comparing it with a complete computer. Change any of it in the calculator.
More head to head: everything the MacBook Air M5 (13-inch), 16GB runs · everything the MacBook Air M5 (15-inch), 16GB runs · every other match-up · the quickest pay-back at each level of use · every model against the frontier