What is a 1000kVA transformer?
A 1000kVA transformer is a medium-sized unit used across commercial and industrial sites: medium-sized factories, commercial buildings and residential complexes all commonly land on this rating. It is a popular size because it sits at the point where a single unit can still serve a whole building without the switchgear and protection complexity of a multi-unit installation.
Typical specifications
Standard ratings
- Power Rating: 1000 kVA
- Primary Voltage: 11kV, 33kV, 35kV, or custom
- Secondary Voltage: 400V / 415V (3-phase, 4-wire)
- Frequency: 50Hz / 60Hz
- Phases: Three-phase
- Cooling: ONAN (oil natural air natural) for oil type
Dimensions and weight (oil-type)
- Length: about 2,000 mm
- Width: about 1,200 mm
- Height: about 1,800 mm
- Weight: about 2,500 to 3,500 kg including oil
These figures are indicative. Actual dimensions and weight depend on the voltage class, impedance, loss specification, tap arrangement and the enclosure or substation package if one is included. For any site with access restrictions or floor loading limits, ask for the drawing for your specific configuration rather than working from typical values.
Other technical parameters
| Parameter | Typical value for 1000 kVA |
|---|---|
| Impedance voltage | 4% to 6% (oil), higher for larger HV class |
| Vector group | Dyn11 |
| Tap range | ±2 × 2.5% off-circuit |
| Temperature rise | 55 K oil / 65 K winding |
| Insulation class | Class A, oil-immersed |
| Sound level | Typically 55 to 60 dB (oil-type) |
Applications of 1000kVA transformers
Commercial buildings
Shopping malls, office buildings and hotels of medium size typically need a 1000kVA unit to cover their total electrical load.
Industrial facilities
Medium-sized manufacturing plants, food processing units and light industry facilities commonly use this rating.
Infrastructure projects
Apartment complexes, hospitals, schools and data centre backup power systems also use 1000kVA transformers.
Renewable energy and auxiliary duty
Smaller solar and wind installations use this rating as a step-up or auxiliary transformer, and industrial plants use it as a station service unit feeding their own auxiliaries.
Oil-type vs dry-type 1000kVA transformers
| Feature | Oil-Type | Dry-Type |
|---|---|---|
| Installation | Outdoor preferred | Indoor suitable |
| Price Range | $7,000 to $15,000 | $10,000 to $20,000 |
| Efficiency | About 98.5% | About 97.5% |
| Noise Level | About 55 to 60 dB | About 60 to 65 dB |
| Maintenance | Regular oil testing | Minimal |
| Fire Risk | Moderate | None |
| Overload capability | Higher thermal mass | More limited |
Price ranges above are indicative planning figures for this rating. Actual cost depends on winding material, loss specification, tap arrangement, enclosure and quantity. See our comparison of oil-type and dry-type transformers for the full decision.
How to size a 1000kVA requirement
- Total the connected load — everything that could draw power, in kW.
- Apply a diversity factor — typically 0.6 to 0.9, since not every load runs at once.
- Correct for power factor — divide kW by the expected power factor, typically 0.8 to 0.95.
- Add growth margin — 20 to 30% for foreseeable expansion.
- Pick the standard rating at or above the result.
Working through that sequence: a site with 720 kW of connected load, a diversity factor of 0.8 and a power factor of 0.9 gives an apparent demand near 640 kVA; adding 25% growth brings it to about 800 kVA, and the next standard rating above that is 1000 kVA. Our capacity calculation guide works the same method through for other ratings.
Installation and protection notes
- Allow space for cooling air and for maintenance access on all sides
- Provide oil containment where an oil-immersed unit is used outdoors or near drainage
- Set protection against overcurrent, earth fault and, for oil units, gas and oil temperature
- Verify tap position and vector group at commissioning
- Record insulation and winding resistance readings as a baseline
Key takeaways
- 1000 kVA is a standard, widely available medium rating with short delivery times.
- Oil-immersed units cost less per kVA and handle overload better; dry-type units suit indoor sites with fire restrictions.
- Size from the load calculation, not from habit, and add a growth margin.
- Loss specification matters more than price at this rating, because these units run continuously.
Browse our power transformers, oil-immersed transformers and dry-type transformers, or contact us with your load details for a quotation.
Protection and switchgear to allow for
A 1000kVA transformer is normally protected as follows, and the requirements should be confirmed against the local code before ordering:
- HV side — fuse switch, circuit breaker or load break switch depending on the network and fault level
- LV side — air circuit breaker or moulded case breaker sized for the transformer’s full-load current plus the overload margin
- Overcurrent and earth fault — settings coordinated with the upstream device so a fault trips the closest device first
- Oil-immersed units — Buchholz relay, pressure relief device, oil and winding temperature trips where fitted
- Dry-type units — winding temperature sensors with alarm and trip contacts
- Surge protection — particularly where the supply is overhead or the site has a poor lightning history
Protection settings should be recorded and kept with the commissioning documents, because future fault investigations depend on knowing what the settings were.
Delivery, siting and installation
Choosing between indoor and outdoor siting
An oil-immersed unit outdoors needs a plinth, oil containment and clearances for cooling and maintenance. Indoors it needs a fire-rated cubicle and ventilation adequate to remove the heat it rejects — a small plant room with no air path will raise the operating temperature and cut the achievable rating. Dry-type units indoors still need ventilation, but no oil containment, and the fire rating requirement is normally lower.
Access for delivery
A 1000 kVA oil-immersed unit weighs roughly 2.5 to 3.5 tonnes including oil, so it needs crane access and a route able to take the vehicle. For basement installations, confirm the lift capacity or the crane position before ordering, not when the truck arrives. Dry-type units at this rating are lighter, which can make an otherwise impossible installation possible.
Lifting and positioning
Use the designated lifting points, keep the unit level, and avoid shock loads. On oil-immersed units, check the radiator and bushing condition after positioning, and confirm the oil level again after the unit has settled.
Running cost: what the losses mean in practice
Two transformers with the same 1000 kVA rating and different loss specifications will have different running costs for as long as they are installed. No-load loss is charged continuously for the whole life of the unit; load loss is charged in proportion to the square of the load. For a unit loaded to about 60% on average, both components contribute meaningfully to the annual energy cost, and over twenty years the difference between a low-loss and a standard-loss design can exceed the initial equipment price difference. Where the purchase is being assessed on total cost rather than capital cost, ask suppliers to state both loss figures so the comparison can be made properly. Our guide to losses and total cost of ownership sets out the calculation.