New · arXiv preprint 2026

Where should agents live?

agentic-eCAL extends eCAL from a single model to multi-agent LLM workflows: every LLM call, tool invocation, retrieval, inter-agent hand-off, and the shared pre-training bill, all in Joules per bit. It answers a question network operators now face: where across the edge-cloud continuum should an agent team run?

<0.25%
Share of workflow energy spent sending inter-agent text over 5G RAN, metro, and optical links
23.9×
More energy for multi-agent topologies vs. a single agent (Qwen2.5-7B), with no consistent gain in task success
R² > 0.99
Two-rate LLM call model vs. measured GPU energy on NVIDIA A100 with vLLM (~10% mean error)
16 · 8
Open-weight models and orchestration topologies characterized
The problem

An agentic workflow is not one big inference.

eCAL costs a single model's lifecycle. Agentic workflows take an off-the-shelf LLM and run it as a directed graph of reasoning steps, tool calls, retrievals, and hand-offs between agents. Three properties change how the energy has to be counted.

No bespoke training

Models are taken off the shelf. eCAL's development cost becomes the model's embodied pre-training energy. That energy is large, but it is shared by every downstream user and amortized over every workflow served.

The unit of work is a workflow

One task triggers a graph of many LLM calls. Each prompt carries the growing transcript, so token volume, and with it energy, can grow super-linearly with the number of steps.

Heterogeneous components

Besides LLM inference, a workflow runs diagnostic tools, vector-database retrieval, and 7-layer OSI transport between agents placed on different network tiers.

The metric

agentic-eCAL generalizes eCAL to multi-agent workflows.

Total workflow energy plus an amortized share of pre-training energy, divided by the useful output bits the workflow produces. With a single call, no tools, and co-located agents, it reduces to eCAL's energy per bit of one inference.

agentic-eCAL= EW + γₑ·(Eemb + Eemb,ret) Buseful [J/b]
EW=(1 + γᵥ)·[ΣEcall+ΣEtool+ΣEret+Etx]

EW is the operational energy of the workflow: every LLM call, tool execution, and retrieval, plus the transmission energy Etx of messages between agents. The transmission term uses eCAL's 7-layer OSI data-collection model. γᵥ is the same virtualization overhead factor eCAL uses.

Eemb is the embodied pre-training energy of the open-weight model, and γₑ = 1/G is its share per workflow when the model serves G invocations. Buseful is the useful output in bits.

Ecall ≈ cpre·pin + cdec(b)·pout
prefillCompute-bound — the prompt is processed in parallel. The rate is flat in batch size, at ≈0.02–0.03 J/token on an A100.
decodeMemory-bound — weights stream from HBM once per batch, so the rate falls as ~1/b toward a KV-cache floor.
E ∝ KᵃSuper-linear in steps — transcripts accumulate, so energy grows with an exponent 1 ≤ a ≤ 2 that rises with serving batch.

Validated on Qwen2.5-7B and Llama-3.1-8B (A100, vLLM continuous batching, 270 configurations per model, 2–30 agents, batch 2–256): R² > 0.99, ~10% mean error.

Key findings

Context costs energy. Sending text between agents barely does.

The findings come from GPU measurements on NVIDIA A100 and H100, 16 open-weight models, 8 orchestration topologies, and an ETSI ZSM-aligned telco edge benchmark.

01

Transport is almost free; context is not

Sending a 2,700-token hand-off over 5G costs about 1/496 of the prefill energy it triggers when it arrives. Distributing agents costs energy mainly through the extra inference and context processing a hand-off causes, not through transmitting it.

02

Energy grows super-linearly

Carrying history raises energy by 32.8% at six reasoning rounds on Qwen2.5-7B. The agent-count exponent rises from 1.10 to 1.42 as batch grows from 2 to 256. Batching cannot outrun the quadratic growth of prefill.

03

KV-cache is effectively non-transportable

Migrating the KV-cache moves 18.9 Gbit per session, compared with 0.33 Mbit for the transcript and 0.051 Mbit for incremental hand-offs. The choice of hand-off protocol spans 3.7×10⁵, compared with 4.8× for the choice of architecture.

04

More agents ≠ more solved tasks

On 24 Kubernetes incidents with Qwen3.5-9B, a single agent costs 17.4 kJ per solved task, against 29–79 kJ for the multi-agent topologies. Only one topology beats Single (64.6% vs. 61.7% solved), and it uses 2.9× the energy.

Placement

Memory decides where agents fit. Bearers barely matter.

A site can host an agent team only if the model weights and every agent's resident KV-cache context fit in its accelerator memory. Moving text between tiers adds a negligible share of energy.

A six-agent chain across the edge-cloud continuum

Far Edge / Device

M ≤ 8 GB
e.g. Orin Nano · models ≤ 3–4B
a1a2Net-CLI tool

Telco Edge / MEC

M ≈ 24–64 GB
e.g. AGX Orin, L4 · models 7B–14B
a3Telco RAG

Core Cloud / DC

M ≥ 80 GB
e.g. A100, H100 · models 27B, 70B
a4a5a6
Energy of a four-agent RAG workflow (Llama-3 8B, A100, b = 64)
Workflow compute EW4 LLM calls, tool, retrieval
≈ 280 J
Hand-offs · loaded edge cellε ≈ 10⁻⁵ J/b
0.52 J · 0.19% of EW
Hand-offs · metro fibreε ≈ 10⁻⁷ J/b
8.9 mJ · 0.003% of EW

Log scale. The three hand-offs carry 1,290 tokens between agents. Hand-off energies and shares are from the paper (Fig. 4d); EW is derived from those shares. Topology after Fig. 1.

Memory is the binding constraint

An 8 GB module loads only two of the three lightest models. At 64 GB and above, all four weight classes fit, including 70B models at 4-bit.

KV width sets serving density

Within the same 8–16 GB weight class, a 10-agent team fits 112 concurrent sessions (GPT-OSS-20B) or as few as 7 (OLMo-2-7B). The difference is set by KV-cache width, not by model weights.

Send increments, keep the cache local

Incremental hand-offs send 6.5× less data than re-sending the whole transcript. KV-cache migration uses more energy than local compute on every cellular bearer.

The paper

Read the full characterization.

arXiv · 2026 · Preprint★ New

Where Should Agents Live? Energy-Memory Characterization of Agentic AI for the Edge-Cloud Continuum

Introduces agentic-eCAL, which generalizes the eCAL metric to directed multi-agent workflows. It couples a closed-form two-rate LLM call energy model with 7-layer OSI data transport, and is grounded in hundreds of GPU benchmark configurations on NVIDIA A100 and H100.

  • agentic-eCAL: a per-bit energy metric for multi-agent workflows across the edge-cloud continuum
  • Two-rate call model (compute-bound prefill, memory-bound decode) validated with R² > 0.99
  • Inter-agent text transport accounts for <0.25% of workflow energy across 5G RAN, metro, and optical links
  • On an ETSI ZSM-aligned telco edge benchmark, multi-agent topologies use up to 23.9× (Qwen2.5-7B) and 4.0× (Qwen3.5-9B) more energy
arXiv:2609.18283 · 16 Sep 2026 · Fortuna, Hanžel, Strnad, Bertalanič — Department of Communication Systems, Jožef Stefan Institute · Submitted to the IEEE JSAC Special Issue on Agentic AI for Intelligent Networks

Code: sensorlab/a-eCAL — to be open-sourced upon acceptance.

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Let's make agentic AI's energy cost measurable.

Deploying agent teams in a network, researching sustainable AI, or interested in extending agentic-eCAL to new serving stacks or accelerators? We'd like to hear from you.