Estimates, not measurements
The calculators on ServerCalc are estimation tools for planning purposes only. They use standard industry formulas and publicly documented vendor specifications, and they are calibrated against published benchmark data, but they are models. Real hardware varies. Always verify against current vendor documentation, and against a meter, before purchasing hardware, committing to a colocation contract, or making safety-critical decisions.
Electrical work
This is the important section.
- Nothing on this site is an electrical design. Circuit sizing, breaker selection, panel loading, conductor sizing, grounding, and PDU distribution must be designed and signed off by a licensed electrician or electrical engineer working to your local code (NEC, IEC, BS 7671, or whatever applies where you are).
- The "servers per circuit" figure applies the 80% continuous-load derate common to NEC-based jurisdictions. Your code, your utility, and your landlord may impose stricter limits. Diversity factors, harmonic loading, and upstream capacity are not modeled.
- Inrush current at power-on is substantially higher than steady-state draw and is not modeled here. A rack that fits within its circuit while running can still trip a breaker when everything restarts at once after an outage.
- UPS and generator sizing involves runtime, battery aging, step-load response, and transfer behavior that go well beyond the VA figure shown here.
Power consumption calculators
- TDP is not power draw. The model scales CPU and GPU power with utilization from an idle floor up to the published TDP. Real package power depends on the specific workload, AVX/AMX usage, memory bandwidth pressure, and the firmware's power management policy.
- BIOS profile matters more than most people expect. A Performance profile that disables deep C-states can add 40 to 80 W at idle over a per-watt profile on the same hardware. The models assume vendor-default balanced or per-watt profiles.
- Fan power is modeled for a normal cold aisle, roughly 22 to 25 °C at the inlet. High ambient temperature, a blocked filter, a failed fan, or a dense GPU chassis in a hot spot can push fan draw far above the figures used here.
- PSU efficiency uses the 80 PLUS internal-redundant curve at 230 V. At 100-120 V input, efficiency is roughly 1 to 1.5 percentage points lower across the curve.
- Efficiency is modeled against a single supply, which matches hot-spare operation. If your platform load-shares across a redundant pair without hot spare, each unit runs at a lower load ratio and real efficiency will be slightly worse than shown.
- Component power figures are representative of enterprise parts. A specific DIMM, drive, or NIC can differ meaningfully from the class average used here.
Cooling and heat figures
- Heat output is derived from IT load on the physical principle that essentially all electrical energy consumed by a server leaves as heat. That part is sound; the sizing decision built on it is not automatically sound.
- Room cooling design depends on airflow management, containment, rack layout, redundancy strategy (N, N+1, 2N), altitude, humidity, and the design ambient for your site. A BTU/hr total is an input to that design, not a substitute for it.
- Size cooling on maximum draw with margin, never on typical draw. The day you need the headroom is the hot day when the chiller is already struggling.
Cost, tariff and carbon figures
- Electricity pricing is whatever you type in. Real bills include demand charges, time-of-use bands, capacity charges, network levies, and taxes that a flat per-kWh rate does not capture. Treat the output as an energy cost, not an invoice.
- Currency selection changes the symbol only. There is no exchange-rate conversion; the result is in the same currency as the rate you entered.
- PUE presets are typical values for a class of facility. Your actual PUE varies by season, load factor, and outside air temperature. Use your own measured figure when you have one.
- Grid carbon intensity figures are national or regional annual averages that change year to year and hour to hour. They are suitable for order-of-magnitude estimates, not for a formal emissions disclosure. Regulated reporting (GHG Protocol, CSRD, SECR) has its own required factors and methodology.
Vendor names and trademarks
ServerCalc references multiple vendors (Dell, HPE, Lenovo, Supermicro, Cisco, Intel, AMD, NVIDIA, Ampere and others) by their product names. These trademarks belong to their respective owners. Use of vendor names here is descriptive; it does not imply endorsement, partnership, affiliation, or sponsorship. This site is not affiliated with SPEC, and SPECpower_ssj2008 results are cited as published third-party measurements.
No professional relationship
This site is operated by an independent publisher, not a licensed electrician, electrical engineer, mechanical engineer, or certified data center design professional. For business-critical, safety-critical, or compliance-driven infrastructure decisions, consult a qualified professional. Use of this site creates no professional or advisory relationship of any kind.