Calculator
Enter your period energy and workload usage. The tool estimates IT power, intensity, emissions, and an energy-only cost view.
Formula used
- IT_energy_kWh = Facility_energy_kWh / PUE
- Average_power_W = (Facility_energy_kWh × 1000) / Period_hours
- Intensity_kWh_per_vCPUh = IT_energy_kWh / vCPU_hours
- Effective_grid = Grid_intensity × (1 − Renewables%)
- Emissions_kgCO2e = Facility_energy_kWh × Effective_grid
The weighted “compute unit” helps compare mixed workloads when vCPU-hours alone is not representative.
How to use this calculator
- Choose a reporting period and enter total facility energy.
- Enter PUE to separate IT power from facility overhead.
- Add your usage totals: vCPU-hours, memory GB-hours, storage, and egress.
- Provide a grid intensity factor and optional renewables percentage.
- Click Calculate, then export CSV or PDF if needed.
If you do not know facility energy, use provider sustainability data or internal metering where available.
Example data table
Sample entries to test the calculator quickly.
| Region | Period (h) | Energy (kWh) | PUE | vCPUh | Grid (kg/kWh) | Renewables % |
|---|---|---|---|---|---|---|
| Mixed | 720 | 1200 | 1.40 | 5000 | 0.42 | 20 |
| EU West | 168 | 260 | 1.25 | 1200 | 0.24 | 55 |
| US East | 24 | 38 | 1.30 | 220 | 0.38 | 30 |
Why power intensity matters
Cloud spend is often optimized in currency, yet watts determine both emissions and reliability limits. Power intensity links energy consumption to delivered compute so teams can compare architectures, regions, and scaling policies on a like-for-like basis. A drop in intensity usually indicates better utilization, fewer idle instances, and reduced overhead from networking and storage. Track the metric alongside latency and availability to avoid “green” changes that degrade service. For example, shifting from always-on fleets to scheduled capacity can cut both bills and carbon without touching customer experience.
Choosing the right time window
Short windows (24–168 hours) reveal operational spikes such as batch jobs, autoscaling misfires, or noisy-neighbor effects. Monthly or quarterly windows smooth variability and are better for trend reporting and procurement decisions. When comparing two workloads, keep the window consistent and include the same weekdays and peak cycles. If you migrate regions mid-period, split the data so grid intensity and renewables assumptions stay materially meaningful.
Interpreting PUE and IT energy
PUE translates facility energy into an estimate of IT energy by removing cooling, power conversion, and building overhead. Lower PUE generally improves the intensity values even if application code stays unchanged. If you only know facility kWh, a realistic PUE estimate still supports comparisons, but document the assumption. Revisit PUE when switching instance families or moving to a different hosting model, because the infrastructure profile changes.
Normalization with workload metrics
vCPU-hours are a common denominator for compute, but memory, storage, and egress can dominate energy for some services. The calculator’s weighted compute unit blends these drivers to reduce bias toward CPU-heavy workloads. Use the per-vCPU value for capacity planning and the per-unit value for multi-service platforms. If your org uses internal “service units,” adjust the weights to match your cost and power contributors.
Using emissions and cost outputs
Emissions are calculated with a location-based factor adjusted by your renewables percentage, producing a practical baseline for dashboards. Use gCO2e per vCPU-hour to benchmark teams and identify services with the highest carbon per outcome. The energy-only cost estimate helps sanity-check efficiency work; large savings often come from reducing idle time, right-sizing memory, and minimizing unnecessary data transfer.
FAQs
1) What is Cloud Power Intensity in this tool?
Cloud Power Intensity is the amount of energy attributed to IT work, expressed per vCPU-hour and per weighted compute unit. It helps compare workloads across different sizes and time windows.
2) Why do you divide by PUE?
PUE estimates how much facility energy actually powers IT equipment. Dividing facility kWh by PUE approximates IT kWh, reducing bias from cooling and power-delivery overhead when you benchmark workloads.
3) What if I don’t know my facility kWh?
Use the best available proxy: provider sustainability dashboards, internal metering, or a chargeback estimate. Keep assumptions consistent across comparisons, and rerun when better data becomes available.
4) How should I pick grid intensity and renewables?
Use a regional emissions factor for the grid you consumed, then set renewables to reflect credible coverage for that usage period. This tool applies a simple adjustment for quick benchmarking, not audited accounting.
5) Why include memory, storage, and egress?
Many cloud services consume substantial energy outside CPU execution. Adding memory GB-hours, storage TB-months, and egress GB into a weighted unit helps normalize multi-service platforms and reduces CPU-centric bias.
6) Can I use the exports for reporting?
Yes. CSV suits spreadsheets and dashboards, while the PDF provides a compact snapshot for reviews. For compliance or ESG filings, follow your provider’s official methodology and audited emission factors.