Gemini 1.5 Flash vs Z.ai: GLM 5.1
Compare real-world API costs for Gemini 1.5 Flash ($0.075/$0.3) vs Z.ai: GLM 5.1 ($1.4/$4.4). Calculate Prompt Caching ROI & Batch API savings.
Gemini 1.5 Flash
- Base Input Rate
- $0.07 / 1M
- Output Rate
- $0.30 / 1M
- Prompt Cache Read
- $0.019 / 1M (-75%)
- Cache Write Surcharge
- $0.00 (Free write)
- Batch API Discount
- -50% Off
- Context Window
- 1,000k tokens
- Quality Index (MMLU)
- 78.9
Z.ai: GLM 5.1
- Base Input Rate
- $1.40 / 1M
- Output Rate
- $4.40 / 1M
- Prompt Cache Read
- $0.26 / 1M (-81.43%)
- Cache Write Surcharge
- $0.00 (Free write)
- Batch API Discount
- -50% Off
- Context Window
- 204.8k tokens
- Quality Index (MMLU)
- 88
Prompt Caching ROI & Write Surcharge Break-Even Analysis
Prompt caching drastically reduces input token costs for static prefixes like system prompts, tool schemas, and document chunks. Compare caching mechanisms between Gemini 1.5 Flash and Z.ai: GLM 5.1:
Gemini 1.5 Flash Caching Profile-75% read discount
- Cached Read Price: $0.019 per 1M tokens.
- Write Surcharge: $0.00 (automatic caching with zero write penalty).
- Minimum Cache Prefix: 1,024 tokens.
- Amortization Rule: Immediate net savings from first cached read call.
Z.ai: GLM 5.1 Caching Profile-81.43% read discount
- Cached Read Price: $0.260 per 1M tokens.
- Write Surcharge: $0.00 (automatic caching with zero write penalty).
- Minimum Cache Prefix: 1,024 tokens.
- Amortization Rule: Immediate net savings from first cached read call.
Batch API 50% Discount Offload vs Real-Time SLA
Asynchronous Batch APIs cut total token expenditures in half (50% off input and output) in exchange for non-realtime execution (up to 24-hour turnaround SLA).
| Model / Architecture | Standard Input / Output | Batch 50% Off Input / Output | Turnaround SLA | Optimal Use Cases |
|---|---|---|---|---|
| Gemini 1.5 Flash | $0.07 / $0.30 | $0.04 / $0.15 (-50%) | 24 Hours max (typically 30m - 2h) | Bulk evaluation, dataset labeling, background summarization |
| Z.ai: GLM 5.1 | $1.40 / $4.40 | $0.70 / $2.20 (-50%) | 24 Hours max (typically 30m - 2h) | Offline document translation, embedding backfills, test suites |
Context Window Escalation & Tiered Pricing Architecture
Massive context windows allow ingesting entire repositories or books, but pricing models differ drastically between flat-rate vendors and tiered step-up pricing.
Provides a 1,000k token context window with a maximum output limit of 8.192k tokens.⚠️ Note: Prompts exceeding 128k tokens double in price to $0.15/1M in and $0.6/1M out.
Provides a 204.8k token context window with a maximum output limit of 131.072k tokens.✓ Flat-rate billing across all prompt sizes up to max context ceiling.
Real-World Production Scenarios: Monthly Spend Projections
Pre-computed monthly engineering bill projections across 3 representative enterprise application workloads:
RAG Knowledge Base & Enterprise Search
100,000 queries/month, 3,500 input tokens (system + 5 retrieved chunks), 400 output tokens, 75% prompt cache hit rate.
Multi-Turn Coding Agent & ReAct Loops
25,000 tasks/month, 8,000 input tokens (accumulating conversation context & tool schemas), 1,200 output tokens, 85% cache hit rate.
High-Throughput Offline Data Extraction
500,000 records/month, 1,500 input tokens, 250 output tokens, 100% batch offload (24-hour turnaround SLA).
Gemini 1.5 Flash vs Z.ai: GLM 5.1
エンタープライズの代表的な3大ユースケース（RAG検索、コーディングAgent、バッチ抽出）で精密試算：
月間推定削減額
Frequently Asked Questions: Gemini 1.5 Flash vs Z.ai: GLM 5.1
Authoritative answers on API rate limits, pricing math, break-even thresholds, and architectural migration.
1Which model is cheaper overall: Gemini 1.5 Flash or Z.ai: GLM 5.1?
At base pricing, Gemini 1.5 Flash costs $0.075/1M input and $0.3/1M output, while Z.ai: GLM 5.1 costs $1.4/1M input and $4.4/1M output. The cheaper option depends on your input-to-output token ratio and whether prompt caching or batch discounts are utilized.
2How does Prompt Caching impact the cost of Gemini 1.5 Flash vs Z.ai: GLM 5.1?
Gemini 1.5 Flash offers a 75% read discount ($0.01875/1M), whereas Z.ai: GLM 5.1 provides a 81.43% read discount ($0.26/1M). High cache hit ratios (>70%) significantly compress the cost delta in agentic and RAG architectures.
3Can I use Batch API with Gemini 1.5 Flash or Z.ai: GLM 5.1 to save 50%?
Gemini 1.5 Flash supports 50% batch offload discounts for asynchronous 24-hour turnaround tasks. Z.ai: GLM 5.1 supports 50% batch discounts.
4What are the context window limits and tiered pricing rules for Gemini 1.5 Flash vs Z.ai: GLM 5.1?
Gemini 1.5 Flash features a 1,000k context window with tiered escalation above 128k tokens. In comparison, Z.ai: GLM 5.1 supports 204.8k tokens with flat per-token pricing.