Shop Power Choice: Single Phase or Three Phase?

Shop owners discuss the relative pros and cons of three-phase and single-phase power supplies. February 6, 2010

I will be assembling a semi-professional woodworking shop (one-off custom furniture work) and Im looking for opinions on the type of equipment I should invest in. Every piece of equipment Im seriously considering purchasing is available in either single phase or 3 phase. The equipment Im looking at is a little more substantial than a standard hobby woodworking shop but not as heavy duty as a production shop. For example, 20 planer, 12 jointer, sliding table saw, and so on. Since I will be renting shop space at first with the goal of eventually owning my shop, Im thinking single phase may be the way to go since single phase is more readily available than 3 phase, and as a single man shop my equipment will not be in use continually. Frankly, the only piece of equipment I can see that really needs to be 3 phase is a wild belt sander, and I dont have the need for one in the foreseeable future.

Would I be smart foregoing the 3 phase equipment and going with single phase? How would resale value be on single phase compared to 3 phase in case I ever want to sell a piece to upgrade?

Forum Responses
(Business and Management Forum)
From contributor R:
3 phase is superior to single phase in every way. It has more power, torque, and is more energy efficient. If you get the shop wired for 3 phase, you can still use it to run single phase, but not the other way around. Buy your machinery used on IRS Auctions and you will save a boatload of money.

From contributor W:
In my area there's a monthly minimum electricity charge for 3-phase service, which I (as a small one-man shop) would rarely or never meet. So for me, 3-phase service would be an expensive luxury, whereas it's a money-saver for large shops. You can use a phase converter to power 3-phase equipment from a single-phase service, but I believe you lose some horsepower.

As noted, used 3-phase equipment is cheaper. It's also usually larger, so consider how much space you'll be renting.

From contributor S:

Does the shop you're going to rent have 3-phase now or is it close by? If so, talk to the power company to see minimum monthly charges. Also ask what the demand charge is. My electric company is not controlled by the PSC, so my rates are quite high. Also keep in mind there is legislation going right now about cap and trade. If that passes, look for electric rates to double within the year. I believe this to affect 3-phase more than single.

From contributor M:
No doubt about it at all - 3 phase. It multiplies your options massively and cuts wire size in your machine runs by a large factor. On top of all that, you can do some insane things with 3 phase VDFs. Go to the ABB web site. Another brand I know of is Delta. I only have one of those, but no less amazing than ABB.

From the original questioner:
Thanks for the replies. I'm going under the assumption that it may be hard to find space with 3 phase available and if it is, the cost of bringing 3 phase into a space I may only be in for a year or two will be high.

From contributor J:
Of course it ultimately depends on where you are and where you're looking for space. In my area almost any industrial/commercially zoned space is going to have 3 phase. It would be rare to find it without. I wouldn't bother looking at spaces that didn't have 3 phase power unless there was something else that made the space so desirable that I'd spend the money to have it brought in.

My power company doesn't charge any crazy fees for having 3 phase. It's $12.09 a month, which is the same as my single phase. And on a monthly basis I spend maybe several dollars on the 3 phase. I think my lighting (single phase) is most likely the bulk of my electric costs. I think I'll have to look into lighting that will run off my 3 phase panel in the future!

A call to the local power company should get you info on basic rates.

I think the advantages of having 3 phase outweigh any negatives (if there are any?) and would always go that route. As for machinery resale, that's a tough one to pin down, especially in today's economy. My rule of thumb is that any machine I buy has to pay for itself. So resale value is of much less importance to me than other factors.

One thing I think most guys here will agree on is that your money goes much, much farther buying used industrial machinery in good condition than new "affordable" stuff. $10k can buy you $10k worth of imports to get you up and running. Or it can buy you $30k or more of well made industrial equipment that you won't likely have to replace. But that's a topic for a whole other post.

From contributor B:
Actual 3 phase power by the electric company was out of the question for me. I'm about 8 miles away from the service. I installed a 30hp rotary phase converter though, and it works great. That way, all my tools that I buy can be 3-phase, and if the opportunity to move to a different location where 3 phase is readily available presents itself, I'm all set.

From contributor A:
The 3 phase machines would have a higher resale value later on down the road and the motors can have more miles put on them than single phase motors, kind of like a diesel engine. Say you wanted to sell a slider or wide belt. The hobby woodworker can't justify the cost of such a machine, but the professional can, and he doesn't want single phase. Buy 3 phase machines - you can always use a converter if you are to run them from your home.

From contributor N:
With 3 phase you could buy a slider or a table saw with a much bigger motor. Just today I was making tapered cherry legs for a bunch of pencil desks I'm making for a B&B. I needed all 9 hp to cut them. A 3 hp single phase table saw would have been underpowered. Then there are those pesky hickory jobs. You can always add on a phase converter if you go single phase. At some point you will run into a deal on a widebelt or a big air compressor, big used shaper, and you'll get hooked on 3 phase.

From the original questioner:
So if I understand correctly, and please correct me if Im wrong, 3 phase is the way to go for the following reasons:

A 3 phase motor can be wired to work as single phase.
3 phase is more powerful than single phase.
3 phase machinery will have a higher resale value than single phase.

So there really is no reason to go with single phase instead of 3 phase.

From contributor X:
My small town does not have three phase. After checking with the power company (this was a few years back), I was told that it would take $3000 a mile and I had 9 miles to run. They expected a hefty return and a guarantee. I did the next best thing that was easy for me. I picked up some army surplus generators. One large three phase, one large single phase, and one medium DC generator. All gasoline operated.

From contributor T:
Contributor J, do you mean your cost for running 3-phase equipment in your shop is only "several dollars" per month? How big a shop and how many machines? I ask due to a running squabble with my landlord, who thinks my sub-metered 3-phase is very low, so jacks me on non-metered single phase. As a result I recently switched my lighting from standard fluorescents to industrial metal halides, which can be run on 3-phase. These are widely available on the re-sale market.

From contributor L:
You said: "A 3 phase motor can be wired to work as single phase."
Not true, but you can convert single phase power to 3 phase.

3 phase is more powerful than single phase.
Again not necessarily true; all 3 phase motors have high starting torque, but thats not true of single phase motors.

3 phase machinery will have a higher resale value than single phase.
Depends on the level of machinery; true for production level, not for hobby, or very small shop.

So there really is no reason to go with single phase instead of 3 phase.
Availability of 3 phase will greatly affect your cost. My new shop was right next to 3 phase power, but the electric company wanted $5,000 to set a 3 phase transformer. I talked to one of their engineers and he gave me tips about how to get the transformer set for little or no cost. List all of my current 3 phase equipment and what I intended to put on line in the next year, and the number of hours of operation for each. I was a bit generous with my estimates! After a couple more negotiations, they ended up setting a transformer at no cost.

I had a 400A Square D I Line breaker panel put in along with two big distribution breaker panels while the building was being built. Expensive! Over the next few years I added enough equipment that they had to replace the original transformer with a larger one. Then I had to have another 400A service brought into the building and more distribution panels. All power is brought in as 208V - 3 phase. All 6 of the distribution panels can provide 120 or 208V single as well as 3 phase. There are now 3 - 380V transformers and one 480V transformer to supply the various machines. I have one 40hp motor that is on 208V - 3 phase that really should be on 480V (you can hear the wires rattle in the conduit when it starts). The I Line panel has big expensive breakers and is required by the local code authority for larger loads.

If anyone is going to move into a new space and put in wiring for industrial level equipment, look at the idea of using bus bar. It is more expensive up front but saves each time you have to move/add equipment. You will need to carefully consider future equipment locations and aisles. Always deal with a commercial electrician, not a residential one. The local electric company puts a $15/month 3 phase fee on regardless of usage. Our bill runs $1000 to $1500/month. Thats cheaper/KWH than in a lot of places. We rarely hit the demand charge because here it is calculated over a 30 minute period, not the really short times that some utilities use. When large motors start there is a considerable power spike. Lots of European equipment comes standard with Y-Delta starters to reduce that spike.

From contributor E:
It's hard to believe one can not find a building with 3 phase installed given the thousands of vacancies currently. The system to look for is a 4 wire 3 phase setup. From that you can power without transformers 3 phase 220, single phase 220, and single 120.

I'm in Los Angeles with just such a setup, and my power bill is $950 a month before I flip the first switch due to equipment charges, customer charges, energy surcharges, and just plain old tax. Usual bill: energy used $135.00, bottom line $1400. This is Los Angeles Dept of Water and Power. But they do tell me I save money over a single phase 220 setup. Right!

From contributor H:
Just wait, cap and trade is coming to a city near you. Carbon taxes passed on to all of us for the coal and gas power generating companies, that will have a hard time becoming clean industries. They will simply pass it on to all of us. The average consumer will pay at least $120 per month more for their electric bill. I wonder what that will do to industry? It won't help the so-called carbon footprint - just generate more money for the government and power companies.

From contributor J:
Some of you guys are in a totally different league then what we're talking here. I'm a one man 2k sq. ft. shop with the usual equipment - 7-1/2 hp dust collector, 6 hp jointer, 9 hp planer, 3/2 hp tablesaws, etc. I have 2 meters and 2 separate panels for my single and 3 phase power. Last month's bill was a whopping $93.02. The customer charge is $12.09 per meter. My 3 phase meter cost all of $1.25 for the month of May. Now that's a bit lighter than usual at 19 KWH. But my average is about 100 KWH and that costs roughly $10.

Some of these guys I think must be talking about shops with dozens or even hundreds of employees. This is really not even relevant to a guy who wants to start a 1 man furniture shop. His bill will likely be much closer to mine than $1k + a month.

From contributor S:
If you plan on staying small, go with a phase converter. We use on average 14,000 kwh per month with an average demand charge of 220.00 per month. Just had an energy audit done. If I go off peak with my 3 phase I won't get hit with a demand charge. Also my kw rate will drop. They won't shut me down before 5 pm. Something you guys should look into.

From contributor O:
Contributor J, depending on your utility it can be very relevant to a small shop. 10 years ago I had rates similar to yours with no demand charge and low service charges. With a 3 - 4 man crew using some fairly high HP machines, the bill used to run $80 to $150 per month. Now the demand charge is $20 per KW averaged every 15 minutes (from what I can tell the highest in our state), 058 cents/kWh (not bad) and about $100 for service charges. (Not bad compared to CA.)

Working by myself, the bill is around $650. With 2 in the shop it goes to $700 - $800 if careful about not running the high HP tools at the same time. With more than 2 working, it is counterproductive to watch the load too much and the bill will be up around $1000.

Our provider is a rural co-op; they have no peak hours or incentives and have embraced green power. This and the cap and trade tax as someone else pointed out will be a nightmare for small commercial users.

I have been working with them to try and get some incentives and peak hours. Their tech installed a recorder on the meter for 2 weeks and has figured out a few more things to save a little.

My advice to the questioner would be to first check with his utility provider to see what all costs are, keeping in mind rates will be going up. The new Phase Perfect converters provide more accurate power than what comes from utilities. You might escape all the extra costs going that direction.

From contributor J:
That is very enlightening. I figured being in the Northeast my rates would be up there, but what you're paying is astronomical! I just added up the charges and I pay .066 KWH with no demand charges for the first 10 KW. Even after the 10KW the fees are pretty small; I didn't hit them last month, so can't say exactly what they are right now.

You're paying more for electric than I pay for gas to heat my uninsulated 2k sq. ft. shop in January! Might be time to look into a windmill! I wonder if your rates are common or an anomaly?

From contributor O:
That right there is the problem with green power. A windmill might run lights and some small tools, but calculate the cost of how many windmills it would take to run my 3 head sander and you will see the true cost of green power.

I am in favor of reducing carbon output and cleaning up the environment, but I think we will be better served by conservation, utilizing our own energy sources, implementing nuclear power and developing the technology of green power further before scrapping all the coal plants.

I think my demand charges are an anomaly, at least in Colorado. I network with a lot of shops across the country; California has it worse for certain. Ours is a consumer owned utility that went through some years of poor management combined with high service growth. They are struggling with costs but are working with me to see what can be done. I can handle the rates now; my shop is efficient enough to offset the costs. The big worry is if they keep jacking up.

From contributor S:
Not counting my demand charge, I pay .084/kwh 3-phase. Can't wait for cap.

From contributor Z:
In the world of woodworking, your world is small in single phase - huge in 3 phase. Best thing about 3 phase for me is that I could replace my single phase machines, and sell them on Craigslist, often for more than the 3 phase machines at auction. Re-sale? For your pro-hobby stuff, single phase is much easier to sell. No one with a garage shop will buy 3 phase. Which means whenever the 3 phase stuff comes up, you may be the only local person willing to buy it. Re-selling it won't hurt either if you bought it well. Single phase restricts you usually to 5hp, not enough for many, many jobs. And if you get too many of those 5hp machines, you are going to run out of panel in a hurry on single phase. 3 phase uses less amperage. It's like going to DSL from dial-up. On the other hand, I paid over 10k to have 3 phase (50hp converter, transformer, panels, disconnects, new service, and a few other things). But there is no way I would ever have a Weinig moulder on single phase. Oh, and keep voltage in mind. If you end up with 440volt equipment, you get another amperage advantage, but need a transformer after that phase converter. As a moulder salesman told me - it's more baggage to carry. But worth it once set up.

From contributor Q:
Just today they mentioned on CNN that the congress was going to vote on their version of the cap and trade bill, so they can go home on recess - it's coming very fast. Clean energy is great stuff; it's called nuclear power, and we need about a dozen new plants. The jobs created would pay family wages for thousands of workers, help clear up the air, have no carbon output, and provide cheap electricity. But the Feds under the Dems killed the backing of construction loans to build any new nuclear plants, so they will not be built as banks will not fund that kind of money without government backed loan guarantees. So much for a real green movement - sounds like it's more of a tax and spend movement. Sure wish they had a mini nuclear power source we could buy. You could run your whole shop during the day, then pop it in the truck or car and power your transportation. Unlimited horsepower, and enough fuel for 10,000 years. Still waiting for fly cars too!

From contributor L:
Contributor O, where are you located? Your electric charges seem high! The "green" solutions will raise the costs even more. Will still have to have just as much coal or nuclear power available. The wind doesn't pay any attention to when you need power, and the sun doesn't shine on demand! Our local utility has been putting in natural gas turbines for peak load, also expensive to run/maintain. Back to hand tools and candles! It would employ more and reduce the landfill requirements. After all, people got along without cabinets and store fixtures for thousands of years.

From contributor O:
There are some ex-Soviet portable nuclear generators that pop up on the black market in Eastern Europe. I would love to have one of those setting in my shop. Talk about a profit center. Run the shop and sell power back to the utility. The neighbors would probably complain.

I am in Colorado. Down the road 30 miles, the rates are not much more than what contributor J's are.