The Real Cost Comparison
Let's put actual numbers on this. Here's what you're looking at for the two main options:
Phase Converter
- Install it yourself or pay an electrician ~$300-500
- Operating cost: $10-30/month on your electric bill
- Lasts 20-30+ years
- Take it with you if you move
- No ongoing fees or contracts
Utility 3-Phase Service
- Depends on distance from existing 3-phase lines
- Monthly demand charges: $50-200+
- Requires permits and utility approval
- Timeline: 2-6 months typically
- Stays with the property if you move
The math isn't complicated. Even if you factor in 20 years of operating costs, the phase converter wins by a huge margin for most home shops and small businesses.
Let's Do the Math: 10-Year Cost
Phase Converter (10HP Rotary)
Utility 3-Phase Installation
That's roughly $32,000 in savings over 10 years. And the converter will probably still be running fine at year 20.
💡 Your Mileage May Vary
Utility costs depend heavily on your location and distance from existing 3-phase lines. Some folks get lucky with $8,000 quotes; others get hit with $75,000. Call your utility for an actual estimate before making a decision.
The Honest Pros and Cons
We sell phase converters, so take this with appropriate skepticism — but here's our honest assessment:
✓ The Good Stuff
- Fraction of the cost of utility 3-phase
- Install it in a day, be running equipment tonight
- No permits required in most areas
- Take it with you if you move
- Powers your entire shop from one unit
- 20-30+ year lifespan with minimal maintenance
- No ongoing fees or demand charges
- Works with any 3-phase equipment including CNCs
✗ The Tradeoffs
- Makes some noise (like a small air compressor)
- Takes up floor space (about 2' × 3' for typical unit)
- Draws power even when idling (~1/3 of rating)
- Static converters only good for occasional use
- Digital converters don't work with VFDs
- Need to size it properly for your loads
When a Phase Converter IS Worth It
You bought a 3-phase machine
Found a great deal on a Bridgeport, lathe, or CNC. The machine was cheap because it's 3-phase. A converter lets you actually use it instead of it becoming an expensive garage ornament.
Starting a shop in a rural area
No 3-phase available for miles. Utility quote came back at $40,000+. Phase converter lets you run professional equipment without the infrastructure investment.
Home shop / hobby machinist
You're not running equipment 8 hours a day, so the operating costs are minimal. The converter lets you buy better used equipment (usually 3-phase) at lower prices.
Small business that might relocate
If there's any chance you'll move in the next 5-10 years, a phase converter makes more sense than a utility installation you can't take with you.
Renting your space
Landlord won't pay for utility 3-phase, and you're not about to invest $20K in someone else's property. A phase converter is your equipment and goes with you.
You have multiple 3-phase machines
One properly-sized converter powers all of them. Way more cost-effective than replacing multiple motors or buying individual VFDs for each machine.
When a Phase Converter is NOT Worth It
We'd rather you make the right decision than buy something you don't need. Here's when to consider other options:
One small motor, easy to replace
If you have a single 1-2HP motor and single-phase replacements are readily available, just swap the motor. It's often cheaper than buying even a small phase converter.
3-phase already available at your location
If you're in an industrial park or your building already has 3-phase service, just use it. Don't add a converter when you don't need one.
Very temporary situation
Moving in 6 months? Need to run a machine just a few times? Might make more sense to rent time at a makerspace or pay a machine shop, depending on your project.
You can sell the equipment easily
If you can sell your 3-phase machine for a good price and buy an equivalent single-phase machine for similar money, that might be simpler. (This is rare, but it happens.)
✓ The "Secretly Worth It" Scenario
Some people think they should just buy single-phase equipment. But here's the thing: the best used machines are almost always 3-phase. A $2,000 converter opens up a whole market of professional-grade equipment at reasonable prices. The converter often pays for itself in what you save on the machines.
Common Questions
How much electricity does a phase converter use?
When idling (running but no load), a rotary converter draws roughly 1/3 of its rated horsepower. A 10HP converter idles at about 3HP worth of electricity — roughly 2.2 kW. At average US electricity rates, that's about $0.25-0.35/hour. Most people run their converters only when using the shop, so figure $10-30/month for a typical hobbyist.
What's the catch? Why doesn't everyone use these?
No real catch — phase converters have been the standard solution for this problem for 50+ years. The main reasons people don't use them: they don't know they exist (lots of people think utility 3-phase is the only option), or they're in a commercial/industrial setting where utility 3-phase makes sense due to scale and the need for backup power.
Will my equipment run as well on converted power?
With a properly sized rotary converter, yes. The output is true three-phase power — your equipment can't tell the difference from utility power. We have customers running Haas CNCs, industrial welders, and precision grinders with no issues. The key is sizing the converter correctly for your loads.
How long until a phase converter pays for itself?
Compared to utility 3-phase installation? Usually less than one year, often immediately. Compared to selling 3-phase equipment and buying single-phase? Depends on your specific machines, but often the converter is cheaper than the loss you'd take selling and rebuying equipment.
Can I install it myself?
If you're comfortable with 240V electrical work, yes. It's connecting wires to terminals — not complicated, but you do need to respect the voltage. If you're not confident, an electrician can install it in a few hours for $300-500. We include detailed installation instructions and phone support.
What if it breaks?
Quality rotary converters rarely break — the idler motor is a simple, robust industrial component. Our Phoenix converters have a 5-year warranty, but the actual lifespan is typically 20-30+ years. If something does fail, it's usually a capacitor or contactor — cheap parts that any electrician can replace.
Still Have Questions?
We're happy to help you figure out if a phase converter makes sense for your specific situation. No hard sell — if you don't need one, we'll tell you.