What size sub panel for a workshop you might ask? Well that depends on how much electrical power draw you require and what kind of equipment you will be using.
The size of a sub panel for a workshop should be a minimum of 60 amps up to 100 amp power feed from your house or main service. This is assuming that you have at least a 200 amp main service. It should be 120/240 volt single phase.
How To Determine What Size Sub Panel For A Workshop
The first step would be to identify how many people would be using the workshop at once. If you plan to just use it for yourself then its pretty hard to use one or two power drawing tools at a time. However if you plan to run a small business from the workshop, then you will have to account for more power loads being used.
In this case you may want to look at having the workshop’s own power service with separate meter from the utility. Sometimes this method can be cheaper than running the power cable underground from your house but that really depends on the situation of your design.
More on what we recommend for panels here.
How Many Amps Do I Need For A Workshop
To actually figure out what size panel for a workshop you will have to do some calculations. Here are some code rules to help. A basic load of 30 watts per square meter. So if your work shop is 20 feet by 30 feet= 600 square feet which converts to 56 square meters= 1,680 watts. This will cover the basic lighting and plugs. About 10 amps for good measure which is calculated at 240 volts.
Here is a table to help you add up the rest of the loads.
| Table Saw | 120 volt | 15 amps |
| Skill Saw | 120 volt | 15 amps |
| Welder | 240 volt | 20 amps |
| Drill Press | 120 volt | 2 amps |
| Grinder | 120 volt | 1 amp |
Long story short if you add all of these up then you will come up with a figure of 63 Amps. This is close enough to a 60 amp sub feed which could be run off your house.
More Factors To What Size Sub Panel For A Workshop
The single most important factor is the size and capacity of the panel itself. Make sure you have at least a 16 circuit panel expandable to 32 circuit for future expansion. Also distance from the house. The 6/3 conductor can be fairly costly if the run from the house underground is much more than 50 feet.
We recommend using an aluminum conductor for your sub feed run. This cable is called ACWU. It is armored and can be buried. Most codes will except this type of larger cable for sub feeds and it is much more cost effective than copper.
How Far Can A Sub Panel Be From A Main Panel
A sub panel can be as far as you like from the main panel source providing that the sub panel has a main breaker or shut off disconnect. There are some cases where the code permits a sub panel without a main breaker.
This would be if the sub panel is part of the same building as the main panel like an attached garage to the house. This way you could have the sub panel as what we call a “load center” but you will quickly find out that a panel with main breaker is usually cheaper than a load center due to demand.
How Many Amps Can A Sub Panel Be?
Well you could take 100 amps from a 200 amp panel or 60 amps from a 200 amp panel. The amperage that you use should be no more than 50 percent of your main power service. So you wouldn’t take 60 amps off a 100 amp panel. It is just too much and you are not leaving yourself enough for the main source.
We have seen cases where a customer has a 400 amp main house service and then draws 200 amps off to the garage or a 200 amp service on the garage and a 100 amp sub feeder to the house.
More on breaker panels here.
Other Tips When Sizing A Sub Panel For A Garage Or Workshop
One word, heat! The heating system if it involves any kind of electricity can quickly take up all of your amperage. Be careful what you choose or you could find yourself running to the house to reset the sub panel breaker leading to the workshop.
Some of those wall mount heaters do give quick heat but can draw up to 50 amps 240 volts. We are by no means saying don’t buy one because on a good note they are very cost effective to purchase. Just be mind full of the name plate data on the back of the heater.
Heating Sources For Your Workshop
A propane or other source of fuel would be beneficial to check out. Some people will use oil stoves, wood stoves propane fireplaces etc. Propane stoves give a quick heat and can be run on smaller tanks.
Another popular method of heating your workshop would be in floor. This is usually run through the floor in the form of pipes and filled with glycol. The source to heat it can be oil fired propane etc.
The classic source of heat would be the wood stove. There is no other heat source that give a nicer heat. We all know that wood stoves can be a lot of work however can be very beneficial cost wise to your total work shop project. Remember to always have a wet certified install approve your chimney.
Personally I have a pellet stove in my workshop. Pellets are relatively cheap, the stove is easy to install and the power draw is less than 2 amps helping reduce the size of your sub panel.
Remember to always hire and consult with a local certified electrician to confirm the size of your electrical project. We in now way recommend that you do electrical work yourself.
