The 60-second version
If you only read one section, read this one.
- Three numbers decide 90% of the spec: the kVA rating, the primary voltage class (typically 15, 25 or 35 kV), and the secondary voltage (120/240 V single-phase, or 208Y/120, 480Y/277 or 4,160 V three-phase).
- “Types” is two different questions wearing one word. Oil-immersed versus dry-type is an insulation and fire-safety decision. Pole-mounted versus pad-mounted is a mounting decision. Most guides list all four as siblings, and that confusion is where bad specs come from.
- Buy a standard kVA rating. In North America three-phase distribution units come in 15, 30, 45, 75, 112.5, 150, 225, 300, 500, 750, 1,000, 1,500, 2,000 and 2,500 kVA. Ask for 900 kVA and you buy custom engineering, a longer wait and a higher price for zero benefit.
- Size from diversified demand, not connected load. Skipping the diversity factor can inflate your kVA by 30–100%. You pay for that mistake twice: once in the purchase price, and every hour afterward in no-load loss.
- Target 60–80% loading at peak. Peak efficiency usually lands around 50–70% loading, and insulation life is happiest below roughly 80%.
- US efficiency is a legal floor with a date on it. The table that applies today is the January 1, 2016 tier. A tighter tier applies to units manufactured or imported on or after April 23, 2029.
- “Meets DOE” is meaningless without the kVA attached. The 2029 curve is not monotonic — a 300 kVA three-phase liquid-immersed unit is held to 99.42% while a 500 kVA unit is held to only 99.38%.
- A lot of transformers sit outside DOE scope entirely. Step-up duty, output above 600 V, tap range of 20% or more, and 50 Hz designs all fall outside the federal definition.
- Amorphous core wins on paper and can lose on site. It typically cuts no-load loss by 60–70%, but it carries a price premium and can run a few dB(A) louder than an equivalent silicon-steel design.
- Budget the clock, not just the money. Ask for a committed manufacturing slot in writing before you sign, not an “estimated” window. In this market the slot is worth more than the discount.
What a distribution transformer actually does
A distribution transformer is the last voltage conversion before electricity reaches a building. It takes medium voltage off the distribution feeder — usually somewhere between 4 kV and 35 kV — and steps it down to the utilization voltage that loads actually run on: 120/240 V in a house, 208Y/120 or 480Y/277 in a commercial or industrial facility.
Two things follow from where it sits, and both of them should shape how you buy:
- It runs 24/7, usually lightly loaded. A distribution transformer is energized every hour of the year whether or not anybody is drawing power. That means no-load loss — the core loss — is a fixed cost you pay forever, and on lightly loaded feeders it dominates lifetime cost.
- It is the transformer people can see and hear. Noise, oil containment, clearances and appearance all become real constraints in a way they never do at a transmission substation.
In the United States there is also a legal definition, and it matters because it decides which units fall under the federal efficiency program. Under 10 CFR 431.192, a distribution transformer has an input line voltage of 34.5 kV or less, an output line voltage of 600 V or less, is rated for 60 Hz, and has a capacity of 10 kVA to 5,000 kVA for liquid-immersed units and 15 kVA to 5,000 kVA for dry-type units. The definition excludes autotransformers, drive isolation transformers, grounding transformers, machine-tool control transformers, non-ventilated transformers, rectifier transformers, regulating transformers, sealed transformers, special-impedance transformers, testing transformers, transformers with a tap range of 20% or more, UPS transformers and welding transformers.
The 60 Hz catch for imported equipment. A 50 Hz unit built for an IEC market is outside the US federal definition, and so are most step-up units and anything with a secondary above 600 V. If you are buying for a US project, say so explicitly in the enquiry — “DOE compliant” on a cut sheet means nothing if the unit isn’t in scope.
For comparison, a power transformer moves bulk power between transmission voltages, is rated in tens or hundreds of MVA, and is almost always a custom-engineered, on-load-tap-changing machine. If your project involves a building, a plant, a solar farm or a feeder, you are almost certainly buying a distribution transformer.
The five types — and the decision that comes first
Here is the thing most guides get wrong. “Types of distribution transformer” is usually answered with a list like pole-mounted, pad-mounted, dry-type, oil-immersed. But those four aren’t comparable. Two of them describe how the windings are insulated; two describe where the box goes. They’re independent axes, and you have to answer them in that order.
1. Oil-immersed (liquid-filled)
The core and coil assembly sits in insulating oil inside a sealed steel tank. The oil carries heat to the tank walls and radiators, which gives the best overload capability and the lowest cost per kVA at larger ratings. Fluid choices matter: mineral oil to IEC 60296 is the baseline; natural ester (IEC 62770) and synthetic ester (IEC 61099) have fire points above 300 °C and buy you real fire-safety margin near buildings and water. Cooling designation runs ONAN → ONAF → OFAF; see our guide to ONAN, ONAF, AN and AF cooling classes. Our S20 series oil-immersed distribution transformer covers 15–31,500 kVA at 6, 11 and 20 kV.
2. Cast-resin dry-type
Windings are cast in epoxy resin under vacuum. No oil means no leakage and no fire load, which is why these go indoors: basements, switchrooms, hospitals, data centres, malls and metro stations. They cost more per kVA than oil and they’re less tolerant of sustained overload, but they are far easier to live with inside an occupied building. Look for IEC 60076-11 environmental/climatic/fire classifications (E2, C2, F1) and, if the room is noise-sensitive, a guaranteed sound-power level per IEC 60076-10. Our SCB13 cast resin dry-type transformer spans 30–5,000 kVA up to 35 kV. For indoor selection detail, see Dry Type Transformer: What It Is & How to Choose.
3. Pad-mounted
A ground-level, locked, tamper-resistant steel cabinet on a concrete pad, with all connections underground. This is a format, not an insulation type — pad-mounts are normally oil-immersed. They’re the default for underground residential and commercial distribution, campuses, and EV charging hubs. Because clearances, pad details, fusing and fluid choice all interact, we covered this one in full in Pad Mounted Transformer: Sizes, Prices & Buying Guide.
4. Pole-mounted
Overhead, hung on a utility pole, usually single-phase or small three-phase. Again oil-immersed in most cases. This is the rural and last-mile workhorse: cheap, simple, easy to swap. Typical ratings run 10–167 kVA single-phase.
5. Amorphous-core
Really a core material rather than a separate type, available in both oil and dry constructions. The core is wound from amorphous metal ribbon instead of grain-oriented silicon steel, and it cuts no-load loss dramatically. It’s usually specified as SH15 in oil and SCBH15 in cast resin — our SCBH15 amorphous alloy dry-type transformer runs 10 kVA to 1 MVA up to 35 kV. More on whether it’s worth it below.
And a sixth option: when one box isn’t enough
If your project needs the transformer plus medium-voltage switchgear, protection and a low-voltage panel, a prefabricated compact substation delivers all of it as one factory-tested assembly. It trades a higher unit price for a much shorter site programme and a single interface to commission. See how that played out on an 11 kV / 33 kV compact substation programme for an overseas utility EPC.
| Where it’s going | Default pick | Why | Choose the other when… |
|---|---|---|---|
| Rural feeder, overhead line | Pole-mounted, oil-immersed | Lowest cost, fastest replacement | Underground is mandated, or aesthetics matter |
| Underground residential / commercial | Pad-mounted, oil-immersed, dead-front | Tamper-resistant, no exposed live parts | Fire code or vault rules make liquid unacceptable |
| Indoor switchroom, basement | Cast-resin dry-type | No fire load, no oil containment | Rating climbs past roughly 2,500 kVA and cost dominates |
| Hospital, school, occupied building | Cast-resin dry-type, low-noise design | F1 fire behaviour, low smoke, quiet | Separate outdoor vault is available |
| Data centre, high harmonic load | Cast-resin dry-type, K-13 rated, N+1 | Harmonic heating handled without derating | Utility service is upstream and harmonics are filtered |
| Lightly loaded feeder, 24/7 energized | Amorphous core | No-load loss is the whole cost story | Site is noise-sensitive, or load factor is high |
| Solar, wind, storage interconnection | Step-up duty (often outside DOE scope) | Inverter harmonics, reverse power flow | See our step-up transformer selection guide |
Standard sizes: the kVA chart
There are two standard rating sequences in the world and they do not overlap cleanly. If you’ve read a sizing chart that starts at 25 kVA and runs 63, 100, 160, 200, 250, 315, 400, 500 — that’s the Indian IS 1180 sequence, and it tells you nothing about what you can actually order for a North American project.
- North America (NEMA / IEEE preferred ratings): three-phase 15, 30, 45, 75, 112.5, 150, 225, 300, 500, 750, 1,000, 1,500, 2,000, 2,500 kVA, with 3,000, 3,750 and 5,000 kVA at the top. Single-phase 10, 15, 25, 37.5, 50, 75, 100, 167, 250, 333, 500, 667, 833 kVA.
- IEC R10 (50 Hz markets): 315, 400, 500, 630, 800, 1,000, 1,250, 1,600, 2,000, 2,500 kVA and upward.
| kVA | FLA @ 480 V | Typical application |
|---|---|---|
| 45 | 54 A | Small office, retail unit |
| 75 | 90 A | Medium commercial, school wing |
| 112.5 | 135 A | Small manufacturing, warehouse |
| 150 | 180 A | Medium industrial plant |
| 225 | 271 A | Hospital wing, campus building |
| 300 | 361 A | Large commercial complex |
| 500 | 601 A | Heavy manufacturing, data hall |
| 750 | 902 A | Large industrial campus |
| 1,000 | 1,203 A | Utility substation, mine |
| 1,500 | 1,804 A | Steel, petrochemical |
| 2,000 | 2,406 A | Major industrial facility |
| 2,500 | 3,007 A | Large substation, utility grid |
Three-phase full-load amps = kVA × 1,000 ÷ (V × √3). Single-phase FLA = kVA × 1,000 ÷ V.
| kVA | FLA @ 240 V | Typical application |
|---|---|---|
| 10 | 42 A | Single rural service |
| 25 | 104 A | Small residential group |
| 50 | 208 A | Multi-family residential |
| 75 | 313 A | Small commercial, irrigation |
| 100 | 417 A | Industrial subpanel, large farm |
| 167 | 696 A | Large pole-mount service |
| 250 | 1,042 A | Small three-phase conversion, large feeder |
| 333 | 1,388 A | Utility distribution |
| 500 | 2,083 A | Large distribution feeder |
The round-up rule is not optional. Manufacturers tool for standard ratings. Specify 900 kVA and you will be quoted a 1,000 kVA unit, with all the cost and footprint of the larger machine. The exception is genuinely large custom units, where a non-standard rating can be justified by process or utility requirements.
How to choose: the five-step sizing calculation
This is the part every guide says is important and then skips. Here is the arithmetic.
Step 1 — Convert every load to kVA
kVA = kW ÷ power factor. For motors where you only have horsepower: input kVA ≈ hp × 0.746 ÷ (efficiency × PF). Typical power factors: 0.85 general commercial, 0.90 industrial with correction, 0.95+ for modern IT equipment.
Step 2 — Apply a demand (diversity) factor
Nothing runs at once. Failing to apply this is the single most expensive sizing mistake there is.
| Facility type | Demand factor |
|---|---|
| Residential | 0.4 – 0.6 |
| Commercial / office | 0.6 – 0.8 |
| Industrial | 0.7 – 0.9 |
| Data centre | 0.9 – 1.0 |
Step 3 — Add growth headroom
15–25% is normal. Some utilities mandate a specific figure, so check the service standard before you pick a number.
Step 4 — Derate for ambient, altitude and harmonics
- Ambient: standard designs assume a 30 °C average / 40 °C maximum ambient. Hotter sites need a temperature-rise class check, and the manufacturer needs the real number up front.
- Altitude: above 1,000 m the air gets thinner and cooling drops. Apply the derating rule in IEC 60076-2 (or IEEE C57.12.00 for ANSI designs) rather than a rule of thumb, and state the site altitude in the enquiry.
- Harmonics: if a meaningful share of the load is on VFDs, UPS or rectifiers, assess the K-factor per IEEE C57.110 and either specify a K-rated unit or oversize a standard one. Our K-factor dry-type transformers for a hyperscale data centre project shows how that gets specified in practice.
Step 5 — Round up to the next standard rating
Then sanity-check the loading: your diversified peak should land at 60–80% of nameplate.
Worked example: 300 kW light-industrial plant
| Step | Calculation | Result |
|---|---|---|
| Motor load, 180 kW @ PF 0.85 | 180 ÷ 0.85 | 212 kVA |
| Lighting and receptacles, 50 kW @ PF 0.95 | 50 ÷ 0.95 | 53 kVA |
| HVAC, 70 kW @ PF 0.85 | 70 ÷ 0.85 | 82 kVA |
| Total connected load | 212 + 53 + 82 | 347 kVA |
| Apply demand factor 0.8 (industrial) | 347 × 0.8 | 278 kVA |
| Add 20% growth headroom | 278 × 1.20 | 333 kVA |
| Size for 80% peak loading | 333 ÷ 0.80 | 416 kVA |
| Round up to standard rating | next standard above 416 | 500 kVA |
Check: 333 ÷ 500 = 67% peak loading. That’s in the sweet spot — good efficiency, real margin, and room for the next production line.
The vector group trap. IEC-world practice defaults to Dyn11 (LV leads HV by 30°). North American distribution practice generally uses Dyn1 (LV lags by 30°) — and ANSI documents don’t use clock notation at all, they use phasor diagrams. Paralleling a Dyn1 with a Dyn11 circulates current and trips protection. Confirm the convention with your utility before you specify.
And don’t stop at kVA. Six more lines decide whether the unit works on day one: vector group, impedance (typically 4–6% for distribution, and this sets your fault level), off-circuit tap range (±2 × 2.5% is the usual default), cooling class, enclosure rating and mounting, and protection coordination. If you’re not comfortable reading these off a drawing, start with How to Read a Transformer Nameplate and Technical Parameters. If the feeder voltage swings, an on-load voltage regulating transformer is worth pricing against a fixed-tap unit.
Efficiency and compliance: the floor moves on April 23, 2029
Federal minimum efficiency for distribution transformers lives at 10 CFR 431.196. Three things matter:
- The tier that applies today is the January 1, 2016 table, for units manufactured before April 23, 2029.
- A tighter tier applies to units manufactured or imported on or after April 23, 2029. The trigger is the manufacturing or import date — not your PO date and not your delivery date.
- Coverage expands. Ratings above 2,500 kVA were previously outside federal scope; from 2029 coverage reaches 5,000 kVA.
| kVA | Manufactured before 4/23/2029 | Manufactured on or after 4/23/2029 |
|---|---|---|
| 75 | 99.03% | 99.22% |
| 150 | 99.16% | 99.33% |
| 300 | 99.27% | 99.42% |
| 500 | 99.35% | 99.38% |
| 750 | 99.40% | 99.43% |
| 1,000 | 99.43% | 99.46% |
| 1,500 | 99.48% | 99.51% |
| 2,000 | 99.51% | 99.53% |
| 2,500 | 99.53% | 99.55% |
| 3,750 | Not covered | 99.54% |
| 5,000 | Not covered | 99.53% |
Look at the right-hand column between 300 and 500 kVA. It goes down. A 300 kVA unit is held to 99.42% while a 500 kVA unit is held to only 99.38% — a bigger transformer is allowed to be less efficient than a smaller one, and the curve steps backward again above 2,500 kVA. Which is why “DOE compliant” is a meaningless claim without the kVA attached.
| kVA | Manufactured before 4/23/2029 | Manufactured on or after 4/23/2029 |
|---|---|---|
| 15 | 97.89% | 98.31% |
| 45 | 98.40% | 98.72% |
| 75 | 98.60% | 98.88% |
| 150 | 98.83% | 99.06% |
| 225 | 98.94% | 99.15% |
| 300 | 99.02% | 99.22% |
| 500 | 99.14% | 99.31% |
| 750 | 99.23% | 99.38% |
| 1,000 | 99.28% | 99.42% |
[Confirm before publishing: DOE amended 10 CFR Part 431 in 2024, and a September 9, 2025 action (90 FR 43371) removed amendments that had taken effect on December 23, 2024, reverting the affected sections to the December 22, 2024 version. Re-check 431.196 and 431.192 against the current eCFR text before any specification is issued.]
Outside the US. IEC 60076 is the global baseline — part 1 general, part 2 temperature rise, part 3 insulation and dielectric tests, part 5 short-circuit withstand, part 7 loading guide, part 10 sound levels, part 11 dry-type. The EU applies Ecodesign Regulation 2019/1783 with a peak efficiency index (PEI). ANSI/IEEE C57.12.00, C57.12.90 and the pad-mount family (C57.12.20, C57.12.34, C57.12.38) govern North America. We broke the choice down in IEC 60076 vs ANSI/IEEE: Standards for Export Transformers.
What losses actually cost you
Every guide says “look at the losses.” Very few show you the arithmetic. It’s four steps:
- No-load kWh/year = no-load watts × 8,760 ÷ 1,000. This runs 24/7 from the moment you energize.
- Load kWh/year = full-load watts × (average load fraction)² × 8,760 ÷ 1,000. The square matters — at half load you get a quarter of the load loss.
- Annual cost = total kWh × your $/kWh.
- Compare against the premium, then decide.
Illustrative comparison, 300 kVA three-phase at 40% average load, 8,760 hours, $0.12/kWh:
| Design | No-load loss | Full-load loss | Annual kWh | Annual cost |
|---|---|---|---|---|
| A — meets the DOE 2016 floor | 480 W | 2,800 W | 8,129 | $975 |
| B — low-loss design | 350 W | 2,500 W | 6,570 | $788 |
Difference: $187/year. Over 30 years that’s roughly $5,600 undiscounted, or about $2,900 at a 5% discount rate.
Now the honest part. The premium for design B is commonly in the low thousands of dollars. Simple payback therefore lands in the 8–20 year range, not the “under 5 years” you’ll see quoted. Loss reduction is a genuinely good buy on 24/7 or heavily loaded sites and a weak one on lightly loaded commercial duty. Run your own numbers with the certified watts from two quotations before you pay for it — and ask for the values per routine test, not from a marketing sheet.
Amorphous core: when it pays, when it doesn’t
An amorphous metal core typically cuts no-load loss by 60–70% compared with grain-oriented silicon steel. Because no-load loss is a fixed 24/7 cost, that sounds like a free win. It isn’t always.
| Situation | Verdict | Reason |
|---|---|---|
| Rural or residential feeder, energized 24/7 at 15–30% load | Strong buy | No-load loss is nearly the entire loss profile; payback is shortest |
| Commercial building, moderate load factor | Marginal | Load loss starts to matter; run the numbers first |
| Industrial feeder running 70%+ loaded | Weak | Load loss dominates and amorphous barely helps it |
| Noise-sensitive site (hospital, school, bedroom-adjacent) | Check first | Amorphous cores can run a few dB(A) louder; ask for a guaranteed sound-power level per IEC 60076-10 |
We wrote about the noise-sensitive version of this problem in Low-Noise Cast Resin Dry-Type Transformers for a City Hospital. That project used a conventional silicon-steel core with vibration isolation rather than amorphous — the quieter answer, not the lower-loss one.
The RFQ checklist
Send this and you’ll get comparable quotes back. Leave half of it out and two bidders will quote the same kVA at wildly different numbers because they’re bidding different machines.
- Rated power: kVA, and whether it’s continuous or with a defined cyclic overload profile
- Voltages: primary and secondary, tap range and tap changer type (off-circuit or on-load)
- Phase and frequency: single or three, 50 or 60 Hz
- Insulation and cooling: oil-immersed or cast resin; ONAN/ONAF/AN/AF; fluid type
- Vector group and impedance: for example Dyn1 or Dyn11, 4–6%
- Winding metal: copper or aluminium — this alone moves price by a meaningful margin
- Site conditions: ambient temperature, altitude, indoor/outdoor, coastal or corrosive
- Enclosure: IP or NEMA rating, pole/pad/vault, cabinet material
- Applicable standard: IEC 60076 or ANSI/IEEE C57, plus any utility specification
- Efficiency: the tier you need, and whether you want certified no-load and load loss values
- Testing and certification: routine tests as a minimum; type or special tests where required
- Delivery terms: Incoterm, destination, and required date
Eight mistakes that show up on the invoice
- Sizing without a demand factor — inflates kVA by 30–100%, and you pay for it in purchase price and no-load losses forever.
- Inventing a non-standard rating — 900 kVA instead of 1,000 buys custom pricing and a longer wait for no benefit.
- Mixing up insulation type with mounting type — you can specify “dry-type pad-mount” and “oil pole-mount”; they’re two decisions, not four options.
- Accepting “DOE compliant” without the kVA attached — the 2029 curve isn’t monotonic, so the claim means nothing without the rating.
- Assuming DOE applies when it doesn’t — a 4,160 V secondary, a step-up unit or a 50 Hz design sits outside the definition.
- Specifying the vector group from habit — Dyn11 in a Dyn1 network blocks paralleling.
- Not telling the manufacturer the altitude or the real ambient — you’ll find out at commissioning, not at FAT.
- Waiting for the PO to reserve a production slot — then paying a rush premium for the same unit.
FAQ
What is a distribution transformer?
A distribution transformer is the final step-down transformer in the power network. It takes medium voltage, typically 4 kV to 35 kV, and reduces it to utilization voltage, typically 120 V to 600 V, for homes, commercial buildings and industrial plants. Under the US federal definition at 10 CFR 431.192 it has an input of 34.5 kV or less, an output of 600 V or less, is rated for 60 Hz, and falls between 10 kVA and 5,000 kVA depending on insulation type.
What are the standard kVA sizes for a three-phase distribution transformer?
In North America the preferred standard ratings are 15, 30, 45, 75, 112.5, 150, 225, 300, 500, 750, 1,000, 1,500, 2,000 and 2,500 kVA, with 3,000, 3,750 and 5,000 kVA at the top of the range. In 50 Hz IEC markets the R10 sequence applies instead: 315, 400, 500, 630, 800, 1,000, 1,250, 1,600, 2,000 and 2,500 kVA.
How do I size a distribution transformer?
Convert every load to kVA by dividing kW by power factor, apply a demand factor of roughly 0.6 to 0.9 depending on facility type, add 15 to 25 percent growth headroom, derate for ambient temperature, altitude and harmonics, then round up to the next standard kVA rating. Target 60 to 80 percent loading at peak.
What is the difference between a distribution transformer and a power transformer?
A distribution transformer sits near the load, steps medium voltage down to utilization voltage, and is generally economical and standardized. A power transformer moves bulk power between transmission voltages, is rated in tens or hundreds of MVA, is usually custom-engineered, and often includes on-load tap changing. The US federal efficiency program covers distribution transformers up to 5,000 kVA; power transformers sit outside it.
Should I choose oil-immersed or dry-type?
Choose oil-immersed for outdoor duty where cost per kVA and overload capability matter, and dry-type cast resin for indoor or occupied spaces where fire load, smoke toxicity and maintenance access matter. Oil-immersed is the default for pole-mount and pad-mount service; cast resin is the default for hospitals, data centres, malls, high-rise basements and transit stations.
What DOE efficiency standard applies to distribution transformers?
For units manufactured on or after January 1, 2016 and before April 23, 2029, the minimum efficiencies in 10 CFR 431.196 apply, measured at 50 percent per-unit load for liquid-immersed and medium-voltage dry-type units and 35 percent per-unit load for low-voltage dry-type units. A tighter tier applies to units manufactured or imported on or after April 23, 2029. Confirm the current tables against the eCFR before issuing a specification, because DOE amended Part 431 in 2024 and removed some of those amendments in September 2025.
Is an amorphous core transformer worth the extra cost?
It depends on the load profile. Amorphous core designs typically cut no-load loss by 60 to 70 percent compared with grain-oriented silicon steel, and no-load loss runs 24 hours a day whether or not the transformer is carrying load. That makes amorphous the better buy on lightly loaded feeders that stay energized continuously, such as rural and residential distribution. On a heavily loaded industrial feeder, load loss dominates and the premium buys much less. Amorphous units can also run a few dB(A) louder, so ask for a guaranteed sound level if the site is noise-sensitive.
What information do I need to get an accurate distribution transformer quotation?
Provide the kVA rating, primary and secondary voltage with tap range, phase and frequency, insulation type and cooling class, vector group, impedance, winding metal, ambient temperature and altitude, enclosure or mounting type, applicable standard, required tests and certifications, and delivery terms. Without the winding metal, efficiency tier and delivery Incoterm, two quotations for the same kVA can differ by a factor of three.
The bottom line
Buying a distribution transformer comes down to a short sequence. Decide the insulation first — oil for outdoors and cost, cast resin for indoors and fire safety. Then pick the format — pole, pad, vault or a compact substation. Then size it from diversified demand, not from a connected-load spreadsheet, and round up to a standard rating. Then fix the compliance date: if the unit will be manufactured or imported on or after April 23, 2029, the tighter DOE table applies, and it applies per kVA rating, not as a blanket claim.
Do those four things and you’ve eliminated most of the ways this purchase goes wrong. Everything after that — copper versus aluminium, ester versus mineral oil, amorphous versus silicon steel — is a trade-off you can price once you know what your load actually looks like.
Next step: send us your load list, site conditions and the standard you’re building to. Our engineers will size the unit, flag anything that doesn’t look right, and return a specification you can send to three bidders and compare line by line. Request a sizing review →