# 200amps to the house - 100amps to the shop... Will it work?



## SuperCubber (Feb 23, 2012)

Hi all,

My wife and I are just getting ready to break ground on a new house. It will include a basement, where I will have a shop (yay!). I have some questions regarding electrical.

- The house is 3500 sqft.
- Basement will be about 1500 sqft, including shop.
- Shop will be set up with a dust collector on 240v, a compressor on 240v, an air cleaner on 240v, and several 120v power tools. Obviously, they won't be running at the same time. I will most likely have the air cleaner, dust collector and another power tool running all at the same time.

Our current plan is to have 200amp service to the house, other a 100amp sub panel for the shop and 2 minisplits (the rest of the basement will be on the main panel). I'm pretty confident that the sub panel will be enough to meet my needs, but I'm a little concerned about whether or not the 200amp service to the house is enough, while I'm also using the shop.

My builder says it's plenty, and when I think about the load on the house, that seems to make sense, but I'd like to get some feedback if any of you are in a similar situation.

Thanks for your time.


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## Unknowncraftsman (Jun 23, 2013)

It should be fine. The real question is the wire size of the service line drop. How close are you to the transformer how many neighbors do you share the transformer with. Your machines will run fine it's the surge when you startup 5hp or bigger.
You don't want to dim the lights in the house every time you start a machine. Big bandsaws and compressors are the worst.
It's not the end of the world to have a soft service but can be annoying. 
This has been my experience here on the west coast.
Good luck


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## Mainboom (Jan 24, 2019)

I have 100 amp to by house and have sub in my shop with 240c. think you will be fine if the builder does not know what your wanting id tell him or fire him lol


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## JAAune (Jan 22, 2012)

Only way to know for sure is to do a load calculation or have the electrician do it. Figure out the maximum amps you'll draw from the shop at any given time and add that to the amp draw of the house to make sure you're not pushing over 200 amps.

In your your shop, it's possible the lights, dust collector, air filter, air compressor and the largest power tool you own will run simultaneously at some point in time.

But chances are, you'll be fine unless your house is full of energy-sucking devices.


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## CaptainKlutz (Apr 23, 2014)

+1 need load calculations run by electrician

Amperage required for typical house depends heavily on appliances with large continuous current draw. 
Eliminate the heavy hitters from your home design and you can live with 50A service, especially due to environmental elimination of incandescent lighting.

List of electric devices that suck electric power:
- Electric hot water heaters 
- Electric heat
- Heat pump (especially skip those with electric emergency backup heaters)
- Double stacked kitchen ovens 
- Separate electric cook top and oven (doubles Kitchen demand calculation .vs. standard 50A single unit range)
- infrared rotisserie oven 
- Electric pizza oven 
- Electric wood smoker
- Air Conditioning
- Swimming pool and/or hot tub
- Outdoor misting pump systems
- Landscape lighting

It's easy to go overboard when designing a new home. Once built/owned 3400 sqft house with 250A service that had many of bells/whistles listed above. I had (2) 48 slot panels completely full of breakers. The load calculations of house/appliances limited the garage shop sub panel to 50A. Fewer kitchen toys or less outdoor demand, and shop could have 100A panel.

Best way to ensure you have enough power for work shop in residential area with normal 200/250A service limitation due shared transformers, is to use petroleum for any heating, and keep kitchen appliances to bare minimum.

Best Luck.


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## wapakfred (Jul 29, 2011)

My last three houses (including this one) had detached shops, and a 200 amp main panel with a 100 amp sub in the shop. You would need some really big loads to exceed that capacity. You can be ultra safe by having the loads calculated, but it would take some big stuff to exceed the 200 amps.


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## GrantA (Jul 19, 2014)

If you're building and it's an option, go ahead and get more from the start. You'll only pay for what you use on a monthly basis. I built abut 7 years ago, had a 400a service put in, I have the meter base feeding 2 200a sub panels, one feeds the house and the other feeds my shop. I ran a 150a service to the shop because that's plenty (40a is for my well which is by the shop). You start adding up things like compressors, refrigerators, freezers, it can get tight quick. I have a full size fridge/freezer in the shop and a 5hp air compressor. One my 5hp DC is finished being built I can pretty well figure with the well if all of that cycled at once which is possible there's 130a right there. Add 1 power tool under a load and there's my whole 150a. Not sustained but needed for a minute. 
Oh and a window unit AC pretty much stays running. I'll eventually put in a mini split but the struggle is real!


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## Oldschoolguy (Nov 6, 2018)

If it were me, I'd have the shop wired at 200 also. In today's world it is better to have to much than not enough….ya never know. Just my 2 cents.


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## BlueRidgeDog (Jan 2, 2019)

Your electrician should give you a workup sheet that shows how he calculated the recommendation. It is impossible to guess if it will work as we don't know what type of heat you have, what type of hot water heater, the size of your air conditioner or heat pump etc.

"if" you have gas heat and gas hot water, then yea you are good. For a one man shop, you will only run one item at at time, plus dust collection and air compression. As such my shop is three 20 amp 220 circuits (tools, dust, air) and two 20 amp 110 circuits (lights and outlets). If you have electric hot water, electric stove, a heat pump and two mini-splits AND a shop of 220v tools…then the numbers would likely push you to 400a service….but don't know as we don't know what you have.

I have a 15 SEER heat pump with electric backup, an electric hot water heater and an electric oven/range and live well with my 200 amp service BUT I am the only one in the house, so nobody is cooking when I am in the shop. The tools are not big draws except on start (my saw will pull 12 amps at turn on and then idle at 9…most other tools are similar).


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## Brawler (Nov 12, 2018)

I upgraded my service in my last house. Just for giggles I put a current probe on each leg of the service panel. I then proceeded to turn on just about everything I could see including oven, stove, and dryer. One leg had 22 amps and the other had 19 amps. My guess is you won't even come close to 100 amps in your shop unless it is a production shop with several employees and electric heat.


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## CaptainKlutz (Apr 23, 2014)

> My last three houses (including this one) had detached shops, and a 200 amp main panel with a 100 amp sub in the shop. You would need some really big loads to exceed that capacity. You can be ultra safe by having the loads calculated, but it would take some big stuff to exceed the 200 amps.
> 
> - Fred Hargis


Load calc is always required IMHO.

Funny, my last 3 houses had 200 or 250 service with attached 3-4 car shop space, and provided max of 50-80A for sub panel in work shop after running load calculations? 
Guess a lot depends on where home is located, size of home, and number of people living in it.

Here in Arizona, stressing 200A service is easy on larger home with big family.
Typical new build 3500-3800 sq ft home will have (3) 2.5 HP HVAC systems (~45A), 7-9 HP of combined motors on pool/spa/misting (~50A), and kitchen average demand load of 60A. The represents 155A continuous service requirement without laundry, baths, lighting, or anything special added.

As I posted before: If have full compliment outdoor toys, and gourmet kitchen, can have issues.

Another challenge lately is electric cars are popular here in AZ. Adding 50A Tesla super charger to garage can be almost impossible with ONLY 200A service in larger home, as the demand calc requires 125% load rating. That is another big load I missed in earlier list. 

as always, YMMV
Cheers!


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## SuperCubber (Feb 23, 2012)

Wow, thanks for all the quick replies.

I apologize for not giving more info. I should have been more patient. I was trying to get the post in before my flight departed. Thanks for your patience.

The heat, range and hot water will be gas. We will have double ovens, but that's about it for fancy toys in the kitchen. We will have an in-ground pool. I estimate the mini-splits will cost me about 25 or so amps from the sub panel, which leaves me with plenty to power the shop.

I don't see any 5hp tools in my future, though I'd prefer not to limit myself. The compressor is 3.7 and my dust collector will probably be in the 2-3hp range. All of my other tools are below 2hp.

The electric car comment has me thinking though. We don't have any immediate plans to get one, but it's plausible that we may venture down that path as time passes in this house.

Thanks again for all the input!


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## firefighterontheside (Apr 26, 2013)

I have a 400 amp service to the house, but only a 200 amp panel. It didn't cost anything for the power company to give me that. This way in the future I can expand and have the power needed. 200 sounds small for a big house, but as said, if you don't have electric heat or hot water and all led lighting it will probably be fine.


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## Woodmaster1 (Apr 26, 2011)

I have a separate 200amp service for my detached garage and 150 for my house. The city lets me have two separate meters with a minimum charge for the second meter but I have never not used more electricity than the minimum.


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## bmerrill (Mar 14, 2018)

Load calculations With a structure that large, you will want 2-200 amp panels for the breaker spaces for the residence no necessary for the load. 100 amp for the shop would be fine.

Have you considered a whole house backup generator? These are becoming popular. If so, discuss with your electrician so it can be rewired for install at a later date. The generator doesn't have to serve the whole house, but the electrician can set up the panels where all of the essential circuits are in one panel for service by the generator/transfer switch and the non-essential in the other.


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## clin (Sep 3, 2015)

Another vote for a proper load calculation.

100 Amps sounds like plenty for the shop, but you mention 2 mini-splits. Are these two separate mini-splits each running a single head, or are each of these each a multi-zone running something like 4-5 head each?

Obviously the larger units require more power, though mini-splits are amazingly efficient.

As an aside on this new home, if you are looking at using mini-splits for the whole house, that's a great idea. I have a 3,600 sq-ft home that came with two 5 ton combo units and it sucks. The house really only needs about 3 tons. And in a large house, even with two units (zones), you just can't get the whole house comfortable at one time.

So it's horribly inefficient (expensive to run) because 2-3X oversized and doesn't really keep the house comfortable because different rooms need different amounts of heating or cooling based on the time of day. A single thermostat or two in my case just can't regulate the temperature throughout a 3,600 sq-ft home.

Bottom line, I will be going to all mini-splits when my units die. I can't justify replacing them at this point, but when they crap out, I won't be replacing them.


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## CaptainKlutz (Apr 23, 2014)

> The electric car comment has me thinking though. We don t have any immediate plans to get one, but it s plausible that we may venture down that path as time passes in this house.
> - SuperCubber


If you are new to electric car world, note of clarification on my previous charger comment: do not absolutely need 50A circuit to charge an electric vehicle. Generally speaking:
Standard slow rate (8-12hr) 220/240V 1PH charger typically needs a 20A circuit 
Fast rate (4-8hr) charger needs 30A-40A circuit depending on model.
Super rate (2-4hr) charger needs 50A circuit

- For older homes, common solution is to duplex the electric dryer outlet in laundry room for 20-30A circuit. 
- Many chargers are able to adjust charging rate based on supply circuit and same unit will support any 20-40A circuit to make installation more flexible. Standard 3-5HP wood working tool circuit charges most electric vehicles really well, when not working wood.
- Not all electric cars can handle full current from a 50A 'super charger' charging station. So planning for one is overkill? Unless maybe you own a Tesla and need to charge after work and before evenings activities.

Cheers!


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## Jared_S (Jul 6, 2018)

Go with a 400 amp service

My house has a 200 amp service and the panel was out of space and needed a sub panel just to finish the normal house wiring.. and that is with gas heat and gas hot water.

400 amp is relatively standard around here now.


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## Jared_S (Jul 6, 2018)

> As an aside on this new home, if you are looking at using mini-splits for the whole house, that s a great idea. I have a 3,600 sq-ft home that came with two 5 ton combo units and it sucks. The house really only needs about 3 tons. And in a large house, even with two units (zones), you just can t get the whole house comfortable at one time.
> 
> So it s horribly inefficient (expensive to run) because 2-3X oversized and doesn t really keep the house comfortable because different rooms need different amounts of heating or cooling based on the time of day. A single thermostat or two in my case just can t regulate the temperature throughout a 3,600 sq-ft home.
> 
> ...


This..

I'm in a similar situation, 5700sqft conditioned. Two zones, Two separate hvac systems. Poor execution and significantly oversized on both. The system located in the attic (don't get me started on that) went T.U. this past summer.. been running on the lower system ever since… Double redundancy apparently.


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## SuperCubber (Feb 23, 2012)

Spoke to the builder and electrician today. We ran through some quick and dirty load calculations and it reassured me that it will be enough power. The main takeaway was having hot water, heat and range on gas eliminates a huge potential electric draw.

firefighterontheside: The electrician said $2500 to go to 400 amp service. Yikes!

bmerrill: We are setting up an "essentials panel" in the garage for the backup generator purpose.

clin: one unit, two heads - these will be for the basement only (at least that's our current plan)

Jared_S: I'm going to explore a little more about doing mini-splits throughout. I'll have a conversation with the HVAC guys about it. I'm very concerned about having oversized units. My cousin is an HVAC contractor (out of town), so I'm going to have him do a Manual J calculation for me.

CaptainKlutz: Thanks for the clarification. That helps.


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## firefighterontheside (Apr 26, 2013)

Super cubber, did he say where the money was going? I only have 200 amp panel in the house, but the wire that comes from the pole and the transformer on my pole will support 400 amp.


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## SuperCubber (Feb 23, 2012)

> Super cubber, did he say where the money was going? I only have 200 amp panel in the house, but the wire that comes from the pole and the transformer on my pole will support 200 amp.
> 
> - firefighterontheside


He said it's a completely different install and a separate box to support the extra amperage.


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## firefighterontheside (Apr 26, 2013)

I suppose the meter base is bigger. Mine is pretty big.


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## Jared_S (Jul 6, 2018)

Interesting that it's an additional $2500. Around here the electric company will upgrade to 400 amp service on existing houses (up to the meter) for free.

A friend just had a 2nd meter/ 200 amp service put in to his detached garage (about 150' of trenching + cable) done through the electric company for $150. They base the subsidy discount on projected future use.


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## SuperCubber (Feb 23, 2012)

> Interesting that it s an additional $2500. Around here the electric company will upgrade to 400 amp service on existing houses (up to the meter) for free.
> 
> A friend just had a 2nd meter/ 200 amp service put in to his detached garage (about 150 of trenching + cable) done through the electric company for $150. They base the subsidy discount on projected future use.
> 
> - Jared_S


I think it's clear that I'm not entirely sure what the cost was related to, but it wasn't from the power company.


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## BurlyBob (Mar 13, 2012)

Something my Electrician buddy did when he wired my garage for 100 amp was to test every power tool in my garage at start up. It's quite eye opening, how many amps a tool draws at start up. As a result in the winter when I'm running space heaters I'm careful to not overload a circuit. I've got a sawdust pump that has a 12amp motor that draws 105 amps at start up! When I run that, it's on it's own circuit.

Having your equipment tested at start up might be something to consider. So you can balance your power usage.


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## jonah (May 15, 2009)

The cost difference in the materials to go with a 400A service instead of 200A isn't huge. I forget what it is exactly, but I looked into it at some point and it was shockingly not a lot more. The electrician is going to be cursing that 2/0 or whatever insane gauge it is no matter what, so what's the difference if it's 4/0 or 2/0?

Check with your electrician to be sure, but I'd lean towards the 400A service, especially considering you might want to hang a 60A electric car charger off it someday.


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## rwe2156 (May 7, 2014)

You've got kind of a "low load" house

Something to consider in the future if you every sold the house having a separate meter and a service in the basement might be a plus.

Talking about loads, did you all know a toaster draws 1400watts?

Check with your electrician, but I think you should wire a kitchen with split outlets - top on one circuit, bottom on another.


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## BlueRidgeDog (Jan 2, 2019)

> I ve got a sawdust pump that has a 12amp motor that draws 105 amps at start up!


Defective motor. I would take it to a motor shop. Could be as simple as a bad start capacitor. That is a fire risk right there.


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## Fresch (Feb 21, 2013)

> The cost difference in the materials to go with a 400A service instead of 200A isn t huge. I forget what it is exactly, but I looked into it at some point and it was shockingly not a lot more. The electrician is going to be cursing that 2/0 or whatever insane gauge it is no matter what, so what s the difference if it s 4/0 or 2/0?
> 
> Check with your electrician to be sure, but I d lean towards the 400A service, especially considering you might want to hang a 60A electric car charger off it someday.
> 
> - jonah


Only 2x the price on the wire alone. Copper or aluminum wire? 
Electrical isn't like plumbing or hvac, we will be back in 40 years to ever get money from that location so we get it now. Plus if we screw up people die. Plumbers you get a turd on the floor.


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## jonah (May 15, 2009)

Yeah, exactly. The wire cost isn't the big expense in running a service - the labor is.

Putting in a 400A service takes almost exactly the same amount of labor as a 200A service.


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## kelvancra (May 4, 2010)

Three electricians indicated I only needed a 100 amp service. However:

Friends drop by to do work and the amps rack up quickly, with two playing at the same time:

10 amps-----30 4' LED's
30+amps-----Shop heat
5 amps-------Radio
15-30 amps----3hp comp (intermittent)
7 amps------Hobby items (copper plating station, oven, .....)
5 amps------Chargers (intermittent) 
15 amp------2 ea 3 hp (four bag) dust collectors
7-30 amps----Tablesaw / Bandsaw / Miter /Planer /Jointer /.......

After checking line draws at the tool (clamp), it was obvious two collectors at the same time ate 30 amps. The HVAC called for 40 and 60 breakers. 30 lights were good for 10 or 15 amps…...

Toss in two circuits on each wall and two separate lighting circuits and, as others said, slots could be a big deal.


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## rockusaf (Feb 13, 2018)

Just started getting quotes myself right now to run power out to the shop and each has said a 100 amp service should be enough but my shop is only around 12' x 24'. I gave one guy a call based on a friends recommendation but as I was explaining what I'm looking for and asking what my options were he just said he was not interested and turned around and walked out, never even got to the point of asking what the recommendations were. Id say the reviews I read about him online were pretty much spot on, glad I figured that out this early. There is power run out to the smaller building but I think how the previous owner ran it is a bit sketchy and they are hesitant to get into that.

Rock


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## jonah (May 15, 2009)

There's no chance you have all of those things going at once. 100A is plenty for the shop. Why would the compressor be running while you're using the dust collector and a tool?


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## Jared_S (Jul 6, 2018)

> There s no chance you have all of those things going at once. 100A is plenty for the shop. Why would the compressor be running while you re using the dust collector and a tool?
> 
> - jonah


Pneumatic clamps.


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## bigblockyeti (Sep 9, 2013)

I had a 60 amp sub panel running to my detached shop and 200 to the house, it worked well for everything I needed. The biggest two things I could think of running at the same time would be a 3hp dust collector and a 3hp something else. Ancillary draws like lighting, radio, small A/C, various chargers all together probably wouldn't be 15 amps so it worked out fine for me. It's always better to have too much capacity up front as it's far cheaper to add it now then later.


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## GrantA (Jul 19, 2014)

> There s no chance you have all of those things going at once. 100A is plenty for the shop. Why would the compressor be running while you re using the dust collector and a tool?
> 
> - jonah


Lots of people leave the compressor running, especially with a bigger compressor hooked to hard lines. Leakage, auto drain etc no telling when it'll cycle.


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## SuperCubber (Feb 23, 2012)

I do plan to leave the compressor running, so that does leave a little uncertainty as to when it will fire up. That said, with some quick math, it looks like the MOST I would ever hit in the shop would be about 50 amps. That's with the compressor going, a 3hp DC, the 1/2hp air cleaner, and my table saw.

I, admittedly, don't know much about mini-split wiring, so it's hard for me to calculate how many amps they will draw. I plan to have one compressor outside and two heads inside. It seems like 25 amps would cover that, but I can't say for sure.

That would leave 125 amps (at peak) for the rest of the house. It seems like as long as I'm not using both ovens at the same time as everything in the shop, it should work out.


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## Jared_S (Jul 6, 2018)

> I do plan to leave the compressor running, so that does leave a little uncertainty as to when it will fire up. That said, with some quick math, it looks like the MOST I would ever hit in the shop would be about 50 amps. That s with the compressor going, a 3hp DC, the 1/2hp air cleaner, and my table saw.
> 
> I, admittedly, don t know much about mini-split wiring, so it s hard for me to calculate how many amps they will draw. I plan to have one compressor outside and two heads inside. It seems like 25 amps would cover that, but I can t say for sure.
> 
> ...


Do you plan on upgrading to larger equipment at any point in the future?

It's pretty easy to end up with a 7.5 hp shaper or panel saw.. or planer or…


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## SuperCubber (Feb 23, 2012)

> Do you plan on upgrading to larger equipment at any point in the future?
> 
> It s pretty easy to end up with a 7.5 hp shaper or panel saw.. or planer or…
> 
> - Jared_S


Good question. Never say never, but I don't think so, at least not in this shop. I'd be limited by space before power in that case.


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