Electronic voltage regulators are typically designed for indoor, low voltage applications and are air-cooled (i.e. using dry-type transformers instead of oil-filled). Other characteristics of tap switching and double conversion EVRs differ substantially so they are listed separately below:
Tap Switching Electronic Voltage Regulators
| Size (kVA): | 3 VA up to 2,000 kVA |
| Nominal Voltages: | Common AC voltages - 120, 208, 240 & 480 at 60 Hz |
| Input Voltage Range: | +10% to -25% (varies by manufacturer) |
| Output Regulation: | +/-2% to +/-5% (varies by manufacturer) |
| Phase: | Single and three phase |
| Voltage Step Up/Down: | Yes |
| Cooling Media: | Air |
| Location: | Indoor |
| Efficiency: | Usually > 95% (see comment below) |
Double Conversion Electronic Voltage Regulators
| Size (kVA): | 3 VA up to 400 kVA |
| Nominal Voltages: | Common AC voltages - 120, 208, 240 & 480 at 60 Hz |
| Input Voltage Range: | +10% to -25% for tap switchers and +10% to -15% for UPS (varies by manufacturer) |
| Output Regulation: | +/-1% to +/-5% (varies by manufacturer) |
| Phase: | Single and three phase |
| Voltage Step Up/Down: | Yes |
| Cooling Media: | Air |
| Location: | Indoor |
| Efficiency: | Usually > 95% (see comment below) |
Efficiency for a tap switching EVR is usually fairly flat across the load range from 10 to 100% of rated load. However, the efficiency for a double conversion EVR tends to drop quickly as the load drops below 100%. Other factors like ambient temperature, power factor, load type etc. can also negatively impact double conversion EVR efficiency.