IBM Power 11 Power Requirements
Every published Power 11 electrical and thermal figure by machine type, what IBM actually measures each machine drawing, and what those numbers mean per rack unit when several go in the same rack.
Most Power 11 power questions are asked one machine at a time and answered from a specification sheet. The harder question, and the one that decides a real deployment, is what happens when several of them go in the same rack. Power 11 is dense enough that the rack power budget, not floor space, is usually the binding constraint. This page gives IBM's published figures per machine type, IBM's own measured draw, and what both mean per rack unit.
Power 11 power requirements by machine type
| Machine type | Model | Operating voltage | Max power | Max thermal | Weight | EIA |
|---|---|---|---|---|---|---|
| 9242-21B | S1112 rack | 100 - 127 or 200 - 240 V ac | 550 W | 1,877 BTU/hr | 20.4 kg | 2U half-wide |
| 9242-21T | S1112 tower | 100 - 127 or 200 - 240 V ac | 550 W | 1,877 BTU/hr | 24.5 kg | Tower |
| 9824-22A | S1122 | 200 - 240 V ac | 2,600 W | 8,871 BTU/hr | 32.2 kg | 2U |
| 9856-22H | L1122 | 200 - 240 V ac | 2,600 W | 8,871 BTU/hr | 32.2 kg | 2U |
| 9824-42A | S1124 | 200 - 240 V ac | 2,950 W | 10,065 BTU/hr | 43.5 kg | 4U |
| 9856-42H | L1124 | 200 - 240 V ac | 2,950 W | 10,065 BTU/hr | 43.5 kg | 4U |
| 9043-MRU | E1150 | 200 - 240 V ac | 5,400 W | 18,245 BTU/hr | 69 kg | 4U |
| 9080-HEU | E1180 | 200 - 208 / 220 - 240 V ac | 4,850 W per node | 16,548 BTU/hr per node | 81.6 kg per node | 5U per node |
All models are single phase at 50 or 60 Hz plus or minus 3 Hz. The E1180 line is per system node; a four-node system multiplies it and adds a 2U system control unit weighing 22.7 kg. Source: IBM Power 11 server specifications.
Watts per rack unit, and why the S1122 is the hard one
Divide the rating by the rack space and the family reorders itself. The machine that stresses a rack hardest is not the enterprise system. It is the 2U scale-out S1122, which packs a 2,600 W rating into two rack units. Fill a rack with those and the power budget runs out long before the rack does.
| Model | Rated max | EIA | Watts per U | Fits in a 20 kW rack | Rack units used |
|---|---|---|---|---|---|
| S1112 (9242-21B) | 550 W | 2U half-wide | 275 W | 36 (power limited) | 36U |
| S1122 / L1122 | 2,600 W | 2U | 1,300 W | 7 (power limited) | 14U |
| S1124 / L1124 | 2,950 W | 4U | 738 W | 6 (power limited) | 24U |
| E1150 (9043-MRU) | 5,400 W | 4U | 1,350 W | 3 (power limited) | 12U |
| E1180 node (9080-HEU) | 4,850 W | 5U | 970 W | 4 nodes (power limited) | 20U plus 2U control unit |
Watts per U is the rated maximum divided by the rack units the machine occupies. The rack capacity column assumes a 20 kW rack budget and no other equipment, which is deliberately optimistic: storage, networking, the HMC and redundancy overhead all draw on the same budget. Two half-wide S1112 machines share a single 2U shelf.
Read the S1122 and E1150 rows together. The E1150 is nominally the bigger machine, but at 1,350 W per rack unit against the S1122's 1,300 W they are almost the same density problem. A rack of scale-out 2U machines is not the easy option it looks like on a floor plan, and the deciding factor is the rack's power budget rather than its height.
Cooling a rack of Power 11
| Rack contents | Rack units | Rated load | Thermal load | Cooling required |
|---|---|---|---|---|
| 7 x S1122 | 14U | 18,200 W | 62,097 BTU/hr | About 5.2 tons |
| 6 x S1124 | 24U | 17,700 W | 60,390 BTU/hr | About 5.0 tons |
| 3 x E1150 | 12U | 16,200 W | 54,735 BTU/hr | About 4.6 tons |
| 4-node E1180 | 22U | 19,400 W | 66,192 BTU/hr | About 5.5 tons |
| 1 x S1124 plus 2 x S1122 | 8U | 8,150 W | 27,807 BTU/hr | About 2.3 tons |
Cooling is calculated at 12,000 BTU/hr per ton of refrigeration. These are rated-maximum figures, so they are a ceiling rather than a steady-state load. IBM's own measured figures run well below the rating, which is why a room designed to the rating alone is usually over-built. Size the circuit to the rating, and the cooling and UPS to the measurement plus margin.
What IBM measures these machines drawing
IBM files measured power figures for each machine type in its EU ecodesign technical documentation, testing a high-end and a low-end configuration. These are the numbers worth sizing a UPS and a rack budget against.
| Machine type | Model | Sockets | Measured idle | Measured maximum | Rated maximum |
|---|---|---|---|---|---|
| 9242-21B / 21T | S1112 | 1 | 216.1 ... 240.1 W | 324.5 ... 449.4 W | 550 W |
| 9824-22A / 9856-22H | S1122 / L1122 | 1 | 319.2 ... 499.5 W | 431.2 ... 999.2 W | 2,600 W |
| 9824-22A / 9856-22H | S1122 / L1122 | 2 | 476.7 ... 860.1 W | 708.6 ... 1,772.5 W | 2,600 W |
| 9824-42A / 9856-42H | S1124 / L1124 | 1 | 602.3 ... 683.5 W | 1,288.8 ... 1,603.4 W | 2,950 W |
| 9824-42A / 9856-42H | S1124 / L1124 | 2 | 820.6 ... 1,018.3 W | 1,807.2 ... 2,501.5 W | 2,950 W |
| 9043-MRU | E1150 | 2 | 855.2 ... 1,145.6 W | 1,784.7 ... 2,332.8 W | 5,400 W |
| 9043-MRU | E1150 | 3 | 1,228.6 ... 1,671.1 W | 2,606.2 ... 3,617.9 W | 5,400 W |
| 9043-MRU | E1150 | 4 | 1,888.3 ... 2,180.5 W | 3,371.3 ... 4,643.0 W | 5,400 W |
Each range runs from IBM's tested low-end configuration to its tested high-end configuration, declared operating condition class A3. Source: IBM Technical Documentation for EU Regulation 2019/424, filed per machine type.
On the two-socket S1122 the measured maximum is 1,772.5 W against a 2,600 W rating. Seven of them rated at 18,200 W measure closer to 12,400 W in IBM's heaviest tested configuration, which is the difference between a full rack and a half-empty one. The processor feature code is what decides where in that range a given machine lands.
Sizing rules that follow from these numbers
- Size the circuit to the rating. Codes and inspectors work from nameplate. An S1124 at 2,950 W on a 208 V feed is about 14.2 A, which is a 20 A circuit per feed at the standard 80 percent continuous-load derating.
- Size the rack budget to the measurement. Rack power budgets are consumed by real load, not nameplate, and the gap between the two is wide on every model except the S1112.
- Redundant feeds double the circuits, not the load. Two supplies share the load so either can carry it alone. Plan two feeds from separate sources, and confirm each rack PDU can carry the whole rack if the other side fails.
- Plan the E1180 per node. Every published E1180 figure is per system node. Size the feed, PDU count and cooling against the populated node count plus the 2U system control unit, never against the single-node figure.
Sources: IBM's Power 11 scale-out server specifications, the E1180 specifications and the E1150 specifications for ratings, and IBM's EU Regulation 2019/424 technical documentation for measured figures. Density, rack-count and cooling figures are calculated from those published numbers.
The processor feature code places a machine inside the measured range above, so confirm it alongside the machine type: the Power 11 CPU reference lists every published option, and the models directory covers the machine types themselves.