Data Center Power Costs and PDU Calculation 2026 | SistemDC

In a dense rack, power becomes a bigger item than the rack rent. Even so, most quote comparisons are made by looking only at the monthly rack price, and the first bill comes as a surprise. This guide explains how a colocation power bill is made up, the conversions between power units, choosing a PDU and the ways of lowering the bill that really work.

Units First: kW, kVA, Amps and kWh

These four units are constantly confused with one another. It is not possible to compare quotes without knowing the difference.

• kW (kilowatt) — real power: The energy the hardware consumes at a given moment. This is the basis for billing.
• kVA (kilovolt-ampere) — apparent power: The total load the circuit has to carry. UPS and generator capacities are expressed in this unit. Conversion: kW = kVA × power factor. In modern server power supplies with PFC the power factor is between 0.95–0.99; 0.9 is used in infrastructure planning to be cautious.
• Amps (A) — current: Fuse and PDU limits are given in this unit. On 220 V single phase: Watts = Volts × Amps. So 1 A means about 220 W.
• kWh (kilowatt-hour) — energy: Consumption spread over time. This is the quantity you see on the bill. A 1 kW load running for 1 hour consumes 1 kWh.

Monthly Cost per Amp Table

The table below is based on 220 V single phase, assuming continuous full load. Your real consumption usually stays below these values.

The Most Expensive Mistake: Going by the Power Supply Label

If you plan by the label value you commit to more power capacity than necessary and overpay. There are three ways to measure real consumption:

• The server's own telemetry: IPMI, iDRAC or iLO interfaces report instantaneous and average power.
• Metered PDU: Gives per-outlet current readings at rack level; the most reliable method.
• Load test: Before going live, run the hardware at full load and record the peak consumption. Measuring only at idle is misleading.

A practical approach: measure average consumption, add a 20–30% allowance for the peak and set your power commitment accordingly.

What Is a PDU and Which Type Should You Choose?

A PDU (Power Distribution Unit) is the unit that distributes the electricity coming into the rack to the equipment. There are four main types:

The last row matters: switches, firewalls and other devices with a single power supply can be connected to only one of the A and B sides. When that side is taken into maintenance, the device shuts down. An ATS PDU closes this gap and gives a single-feed device dual-source redundancy.

PDUs also fall into two groups by the space they take up in the rack: vertical (0U) models sit in the rear channel and do not reduce usable U; horizontal models take up 1U. For layout planning, see the U calculation guide for details.

A+B Redundancy and the 80% Rule

In SistemDC racks, dual PDUs (A+B) provide redundant feeds. On servers with dual power supplies the first cable is connected to side A and the second to side B. The aim is for the system to keep running when one side is taken into maintenance or fails.

Two engineering rules come into play here:

1. The 80% rule: Continuous load should not exceed 80% of the fuse rating. On a 16 A circuit the current that can be drawn continuously is 12.8 A, i.e. about 2.8 kW. This is a standard safety margin in electrical installations.
2. Redundancy margin: The A and B sides share the load. When one side fails completely, the other must be able to carry the whole load on its own. For that reason, in normal operation each side should carry no more than half of its own continuous capacity.

The Difference Between Capacity and Consumption

Rack plans can be provisioned with power capacity from 2 kVA up to 20 kVA. This is the ceiling value; it is not reflected directly in the bill. In the metered model what you pay is the real consumption read from the meter.

In shared rack plans the model is different: power is included in the price but there is a ceiling (~220 W for Starter/Business/ATX, ~440 W for Advanced). If your hardware draws more than this limit you need to move to the metered-power rack model. For a plan comparison, see the rack rental prices guide for more.

Ways to Lower the Power Bill

1. Power supply efficiency: 80 Plus Platinum or Titanium certified PSUs run at 94–96% efficiency at typical load. Compared with a Bronze PSU, the difference more than covers the cost of the PSU over the years in a 1 kW rack.
2. Consolidation: Virtualization on one powerful server instead of three lightly used physical servers saves both U and watts. Even an idle server draws 80–100 W.
3. Blanking panels: Closing off empty U prevents hot air recirculation, lowers the inlet temperature and reduces fan speeds.
4. CPU power profile: For workloads that do not need full performance all the time, a balanced power profile noticeably lowers peak consumption.
5. Remove unnecessary hardware: Unused extra disks, old RAID controllers and disabled network cards quietly consume watts.
6. Tidy up the cabling: A tangle of cables blocking airflow at the rear panel makes the fans spin up needlessly.

We covered the industry's general direction on this in the 2026 data center trends article.

Frequently Asked Questions

How much does a 1 kW server cost in power per month?
1 kW × 720 hours = 720 kWh. At 13₺/kWh that comes to 9,360₺.

How do I convert kVA to kW?
kW = kVA × power factor. A cautious value of 0.9 is used in planning; 10 kVA corresponds to about 9 kW.

Do I pay if I do not use the capacity I am allocated?
Not in the metered model — you pay for the consumption read from the meter. Capacity only defines the upper limit.

What is PUE?
Power Usage Effectiveness is the ratio of a facility's total energy consumption to the consumption of its IT equipment. The closer it gets to 1.0, the lower the cooling and distribution losses. Cold-aisle containment architecture is one of the main practices that improve this ratio.

Can I see my server's current consumption remotely?
Yes. The IPMI/iDRAC/iLO interface provides power readings; if a metered PDU is used it can also be tracked at outlet level.

I have a single-PSU server — how is redundancy provided?
An ATS PDU provides automatic transfer between the A and B sides. This way a single-feed device also benefits from the dual-source infrastructure.

Related SistemDC Guides

• Rack Rental Prices 2026
• What Is a Rack Unit (U)? Calculating Rack Size
• What Is Colocation? Server Colocation Guide
• What Is a Tier 3 Data Center?
• Colocation Provider Selection Checklist
• How to Choose a Data Center Location
• Private cage or shared rack?