Sizing and budgeting are actually one job
Buying a distribution transformer means answering two questions: how big (what kVA rating) and how much (what budget). Most buyers treat these as separate exercises — first a sizing calculation, then a separate round of price hunting. They are in fact one continuous chain: start from your load, apply one formula to reach the kVA, round up to a standard rating, and read the price straight off a reference table.
This guide walks you through the full chain with real 2026 FOB Qingdao prices, so you finish with both a rating and a number you can put in your budget.
Step 1 — Know your total connected load (kW)
List every piece of equipment the transformer will feed and add up their rated power in kilowatts (kW). For motor loads use the motor nameplate rating; for lighting and heaters use the connected wattage. Be honest about which loads run simultaneously — in most facilities the maximum simultaneous demand is well below the sum of all nameplates.
Step 2 — The core formula
Transformers are rated in kVA (apparent power), not kW (real power). The bridge between them is the power factor and the load factor:
kVA = kW ÷ (Power Factor × Load Factor)
Two practical numbers you need:
Power factor (PF): how efficiently your load converts current into useful work. Motor-heavy plants sit around 0.80–0.85; lighting and modern electronics can reach 0.90–0.95. Use 0.8 for a conservative estimate unless you know otherwise.
Load factor: how much of the transformer's capacity you plan to use at peak. Industry practice is 60–80% — enough headroom for starting surges and future growth without overspending on unused capacity.
The quick rule of thumb: if you do not want to run the calculation, plan for roughly kVA ≈ kW × 1.25. This assumes PF 0.8 and a 100% load factor, so it is the conservative upper bound.
Step 3 — Round up to a standard rating
Transformers are manufactured in standard capacity steps. Compute your kVA, then choose the next size up:
| Computed kVA | Select Standard Rating |
|---|---|
| Up to 100 | 100 kVA |
| 101 – 200 | 200 kVA |
| 201 – 315 | 315 kVA |
| 316 – 500 | 500 kVA |
| 501 – 630 | 630 kVA |
| 631 – 800 | 800 kVA |
| 801 – 1,000 | 1,000 kVA |
| 1,001 – 1,600 | 1,600 kVA |
| 1,601 – 2,000 | 2,000 kVA |
A common mistake is over-engineering "just to be safe." Every step up in rating is a step up in price — sizing for 110% of a realistic peak demand is sensible; sizing for 150% because the load was guessed too high just wastes money.
Step 4 — Oil-immersed or dry-type?
Your rating stays the same; your technology choice is driven by the installation environment:
| Factor | Oil-immersed (S13-M) | Dry-type (SCB13) |
|---|---|---|
| Best location | Outdoor, substations, plants | Indoor, buildings, data centres |
| Fire / oil risk | Contains insulating oil | No oil, self-extinguishing |
| Maintenance | Periodic oil checks | Minimal |
| Relative price | Lower | Higher (approx. +15–47%) |
| Typical capacity range | 100 – 6,300 kVA | 100 – 2,000 kVA |
Simple rule: if it sits outside or in a dedicated substation, choose oil-immersed and save money. If it sits indoors near people or fire-sensitive equipment, choose dry-type.
Step 5 — From kVA to budget: real FOB prices
Once you know the rating and technology, the budget number is a lookup. These are 2026 FOB Qingdao reference prices for standard copper-wound designs (10 kV / 0.4 kV, IEC 60076):
| Capacity | Oil-immersed S13-M (USD) | Dry-type SCB13 (USD) |
|---|---|---|
| 100 kVA | $1,881 | $2,672 |
| 200 kVA | $2,750 | $3,852 |
| 315 kVA | $4,085 | $4,786 |
| 500 kVA | $5,655 | $6,472 |
| 630 kVA | $6,965 | $8,690 |
| 800 kVA | $7,730 | — |
| 1,000 kVA | $8,534 | $12,490 |
| 1,600 kVA | $12,606 | $18,546 |
| 2,000 kVA | $15,447 | $21,036 |
Prices are copper-adjusted against a base LME copper price of $14,185/ton; every ±$1,000/ton move in copper shifts these numbers by ±3%.
Don't forget the extras
The FOB price is the transformer at the port of Qingdao. Your full project budget also needs:
Freight & insurance: ocean freight by weight/volume and marine insurance, roughly 5–15% of FOB depending on route and rating.
Import duties & taxes: vary widely by country — check your local tariff schedule before you budget.
Inland transport: port to site, including crane/lifting at the destination.
Accessories & installation: tap changers, temperature controls, enclosures, cables, commissioning.
As a planning rule, add 30–50% on top of the FOB price to arrive at a realistic installed-cost budget.
Two worked examples
Example 1 — Small factory: total connected load 180 kW, power factor 0.85, planned load factor 75%. kVA = 180 ÷ (0.85 × 0.75) = 282 kVA. Round up to 315 kVA. Oil-immersed S13-M at 315 kVA: $4,085 FOB. Budget roughly $5,500–6,000 for the delivered and installed project.
Example 2 — Commercial data room: computed demand 480 kW, power factor 0.95, load factor 80%. kVA = 480 ÷ (0.95 × 0.80) = 632 kVA. The standard step below is 630 kVA — just 2 kVA short — so you must round up to 1,000 kVA. Dry-type SCB13 at 1,000 kVA: $12,490 FOB. Notice how close to the edge a rating can sit: recompute your numbers with real data before finalising, because one kVA too many is a step up in price.
Don't ignore loss costs — the hidden half of the bill
The purchase price is only half the story. Over a 30-year life, no-load and load losses consume electricity 24/7, and their capitalised cost frequently exceeds the transformer's purchase price. That is why loss class matters: S13 low-loss units cost a little more than S11 but save substantially every year, and S20 amorphous-core designs push efficiency even higher. If you are budgeting seriously, always ask your supplier for the no-load loss (W) and load loss (W) figures and run a simple TCO comparison before you buy.
Get your exact number
For the full 2026 selection and price guide with an interactive quote calculator and copper-linked live pricing, open the QDTB Distribution Transformer Selection & Price Guide 2026. For a binding FOB Qingdao quotation, send us your load data, voltage, frequency, and target loss class — we will confirm the rating and price the same day.