Comprehensive sizing chart for dead-front padmount transformers. Find specifications, dimensions, concrete pad
requirements, and selection guidelines for all standard kVA ratings.
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Padmount transformers are the most common type of distribution transformer used in residential subdivisions,
commercial buildings, and industrial facilities across North America. This comprehensive sizing chart
helps engineers, contractors, and facility managers select the correct kVA rating based on load requirements and
installation constraints.
suitable for installation in public areas without additional barriers.
Single-Phase Padmount Transformer Sizing Chart
Single-phase padmount transformers are typically used for residential distribution and small
commercial applications. Primary voltage: 12470GY/7200V, Secondary: 120/240V.
| kVA | Dimensions (HรWรD) | Weight (lbs) | Oil (gal) | Pad Size | Specs |
|---|---|---|---|---|---|
| 25 kVA | 24″ ร 32″ ร 33″ | 604 lbs | 30 gal | 44″ ร 44″ | View Details โ |
| 37.5 kVA | 26″ ร 34″ ร 34″ | 750 lbs | 37 gal | 48″ ร 48″ | View Details โ |
| 50 kVA | 28″ ร 36″ ร 37″ | 900 lbs | 44 gal | 52″ ร 52″ | View Details โ |
| 75 kVA | 30″ ร 38″ ร 39″ | 1,100 lbs | 56 gal | 56″ ร 56″ | View Details โ |
| 100 kVA | 32″ ร 40″ ร 41″ | 1,300 lbs | 70 gal | 60″ ร 60″ | View Details โ |
| 167 kVA | 36″ ร 44″ ร 45″ | 1,700 lbs | 95 gal | 68″ ร 68″ | View Details โ |
Three-Phase Padmount Transformer Sizing Chart
Three-phase padmount transformers serve commercial buildings, industrial facilities, and utility
substations. Primary voltage: 12470GY/7200V.
| kVA | Dimensions (HรWรD) | Weight (lbs) | Oil (gal) | Pad Size | Secondary | Specs |
|---|---|---|---|---|---|---|
| 75 kVA | 36″ ร 50″ ร 44″ | 1,400 lbs | 58 gal | 60″ ร 60″ | 208Y/120V | Details โ |
| 112.5 kVA | 38″ ร 54″ ร 46″ | 1,800 lbs | 78 gal | 66″ ร 66″ | 208Y/120V | Details โ |
| 150 kVA | 40″ ร 58″ ร 48″ | 2,150 lbs | 100 gal | 72″ ร 72″ | 208Y/120V | Details โ |
| 225 kVA | 42″ ร 62″ ร 50″ | 2,600 lbs | 130 gal | 78″ ร 78″ | 208Y/120V | Details โ |
| 300 kVA | 44″ ร 66″ ร 52″ | 3,100 lbs | 156 gal | 84″ ร 84″ | 208Y/120V | Details โ |
| 500 kVA | 48″ ร 74″ ร 56″ | 4,200 lbs | 225 gal | 96″ ร 96″ | 480Y/277V | Details โ |
| 750 kVA | 54″ ร 82″ ร 62″ | 5,600 lbs | 290 gal | 108″ ร 108″ | 480Y/277V | Details โ |
| 1000 kVA | 60″ ร 90″ ร 68″ | 7,200 lbs | 370 gal | 120″ ร 120″ | 480Y/277V | Details โ |
| 1500 kVA | 66″ ร 98″ ร 74″ | 9,600 lbs | 502 gal | 132″ ร 132″ | 480Y/277V | Details โ |
| 2000 kVA | 72″ ร 106″ ร 80″ | 12,400 lbs | 647 gal | 144″ ร 144″ | 480Y/277V | Details โ |
| 2500 kVA | 78″ ร 114″ ร 86″ | 15,300 lbs | 780 gal | 156″ ร 156″ | 480Y/277V | Details โ |
Concrete Pad Requirements by kVA
Every padmount transformer requires a properly designed concrete foundation pad. The pad must be
level, reinforced, and fully cured before transformer installation.
| kVA Range | Minimum Pad Size | Pad Thickness | Concrete Strength | Curing Time |
|---|---|---|---|---|
| 25-50 kVA | 44″ ร 44″ to 52″ ร 52″ | 4 inches | 3,000 PSI | 28 days |
| 75-167 kVA | 56″ ร 56″ to 68″ ร 68″ | 4-5 inches | 3,000 PSI | 28 days |
| 225-500 kVA | 78″ ร 78″ to 96″ ร 96″ | 5-6 inches | 3,500 PSI | 28 days |
| 750-2500 kVA | 108″ ร 108″ to 156″ ร 156″ | 6-8 inches | 4,000 PSI | 28 days |
routing and duct bank locations with utility before pouring concrete.
How to Select the Right Padmount Transformer Size
Step 1: Calculate Total Connected Load
Add up all electrical loads that will be served by the transformer:
- HVAC systems (largest load, consider starting current)
- Lighting and receptacles
- Motors and machinery
- Future expansion (typically 20-25% reserve)
Step 2: Apply Demand Factor
Not all loads operate simultaneously. Apply appropriate demand factors:
| Application | Typical Demand Factor |
|---|---|
| Residential | 40-60% |
| Commercial Office | 60-70% |
| Retail/Restaurant | 70-80% |
| Industrial | 70-85% |
| Data Center | 80-90% |
Step 3: Select Transformer Size
Formula: Required kVA = (Total Connected Load ร Demand Factor) รท Power Factor
Select the next standard size above your calculated requirement to allow for load growth.
factor.
Required kVA = (180 ร 0.70) รท 0.9 = 140 kVA โ Select 150 kVA three-phase padmount
Frequently Asked Questions
What is the most common padmount transformer size?
For residential subdivisions, 25-50 kVA single-phase units are most common. For commercial
buildings, 150-300 kVA three-phase is typical.
How much does a padmount transformer weigh?
Weights range from 604 lbs (25 kVA) to over 15,000 lbs (2500 kVA). Heavy units
(>2000 lbs) require crane installation.
What voltage do padmount transformers use?
Most utility padmounts use 12470GY/7200V or 24940GY/14400V primary. Secondary is typically
120/240V (single-phase) or 208Y/120V / 480Y/277V (three-phase).
Related Resources
๐ More Reference Charts:
- Padmount Full Load
Amps Chart โ FLA for all voltages - Pad
Mounted Transformer Complete Guide โ Types, components, installation
Standards & References
- IEEE C57.12.28 โ
Pad-Mounted Equipment Enclosure Integrity - IEEE C57.12.34 โ
Requirements for Pad-Mounted Transformers - DOE 10 CFR 431 โ Energy Conservation Standards
Disclaimer: Specifications shown are typical reference values per IEEE standards. Actual specifications vary by
manufacturer. Always consult manufacturer datasheets and local utility requirements. Last updated: January
2026