adding sub panel just for new charging circuit?

My existing panel is full, and I believe it is only a 100W panel, home is ~20 years old. There's NO 240v existing any where I can find. I am pretty sure I need to add a new panel (might as well add a 200W panel to keep up with modern standard?), but the charging location is the corner of the house and possibly not all that useful to the rest of the house, so should I just get a simple breaker/dedicated panel instead? Thinking about adding a 6-50 outlet and just use the gen 2 mobile charger with nema plug w/o shelling out for HPWC.

1. add new 200w panel
2. add small panel, upgrade main panel in the future as needed.
3. do something else, I am missing something.


  • Ok, first let's clean up some minor misunderstanding. You likely have a 100 amp service. 100W service would only light one bulb :). Next, I'm about 99.9% sure you have 240V service. The power is in two split phases, where half of your house is on one phase (120V) and the other half is on the second phase (120V). If you have a major electrical appliance such as a dryer, range, oven, or cooktop - these will use 240V. You might notice one breaker is doubled up - this is for 240V.

    100 amp service is rather small nowadays. I had it as well, and upgraded to 200 amp service and replaced my very outdated 40-year old breaker panel. This is a large and expensive job.

    Ok, options include:

    1) Upgrade to 200 amp service. If you are thinking of adding a major electrical appliance, like HVAC, this might be the best choice, but it is expensive.

    2) Depending on the panel, there are 1/2 breakers that can replace full breakers. What this means is you might be able to remove some of the old breakers and insert 1/2 breakers that provide more options. For example, you replace 2 full-size breakers with 4 1/2 size breakers (they often come in a group of 4). You can then wire the original two circuits to the new breaker and have two additional new breakers for your EV. This is the cheapest solution.

    3) Install a sub-panel. This is a reasonable option when the breaker panel is full.

    Options 2 & 3 may limit when you can charge, but that's not much of a restriction. You can schedule the car to charge at midnight when a few other appliances would be in use. If your utility has time-of-day pricing, it will also be the cheapest time to charge. An electrician can do an analysis to see if you can live with 100 amp service.

    My home wiring guide may be helpful too - it also has diagrams to better explain some of this:
  • > @CAYorCYA said:
    > My existing panel is full, and I believe it is only a 100W panel, home is ~20 years old. There's NO 240v existing any where I can find.

    To add to what TeslaTap wrote, a 20 year-old home could have, should have, a 200 amp service. What capacity is marked on the main breaker? Are there any unused positions in your panel?

    Thanks for the replies, here's an image of the current panel. There's additional stuff outside of the house, as I also have solar... Maybe that one is more interesting to look at now that i think about it. Will try to take a pic of that.
  • You have 3 240V circuits.
    One for 30A, upper left.
    One for 20A, middle left That is an unusual setup as it combines one single pool breaker with one of the pool of a tandem breaker, never seen that before.
    One 40A, lower right.
  • @CAYorCYA - While I can't say if you can add a NEMA 14-50 circuit (50 amp 240v breaker) and meet code, there is room in the breaker box to replace some of the dual breakers with quad breakers. You need to talk to an electrician to do a load analysis and know what options meet code. Perhaps it will not work with a 50 amp circuit, but a 30 amp circuit could be all you really need (24 amp charging).

    I strongly suggest any work is done with appropriate building permits. This helps ensure the work is done correctly. Without permits, your insurance might not cover a problem/fire if caused by unpermitted work.
  • Even if your house is 20 years old, chances are you have a 240V, 30A electric dryer outlet. If it is convenient to where you will be parking the car, you can charge from that and save the time and money to upgrade your existing electrical service. It will charge a little slower than a 50A circuit, but may still be fast enough to meet your needs.
  • @stevenmaifert,
    Many houses in CA only have gas outlets for their dryers. Gas used to be close to free in CA.
  • Here is my Main panel,
    I did learn a bit by talking to few electricians also, but am getting conflicting info.

    Can I easily add a new sub off the main?

    Guy 1 says yes, but also recommended adding wall charger either from tesla or chargepoint. Can install socket, but will cost more than charger hardwired.

    Guy 2 said no. Due to the sticker showing solar "do not relocate".
    He suggested I add or upgrade the existing sub, and run a conduit out for the socket.

    I know this comes down to a personal choice, but I am looking at it from a socket will give me years of flexibility, as no matter what car I buy I will likely be able to use a 6-50 socket.

    I am going with Guy 2, but want to learn more as work hasn't start yet.

    Finally, is 6-50 a better choice as 14-50 although common, isn't really useful unless I buy an RV (which is not going to happen since I don't have a place to park near it). 6-50 is less wiring and the receptacle is also cheaper, so it is my choice. Anything wrong with this line of reasoning?
  • @CAYorCYA, that doesn't look like your MAIN panel. If that is your main panel then evidently you ONLY have a solar circuit, with no outlets, no lights, no appliances...
  • @derotam - He posted the sub-panel picture earlier. It appears there are already two panels.

    @CAYorCYA - I'm not an expert, but I've done quite a bit of electrical work (via permits) over the years. I expect you can add a subpanel, but as I said earlier, it may not be necessary if you change some of the existing breakers to quad breakers.

    While I installed a NEMA 6-50, if I were to do it over, I'd go with the NEMA 14-50. It's not a huge deal either way, but the 14-50 is more common nowadays and you are right that the 6-50 is a bit cheaper as no neutral wire is needed.

    If you decided you want 40 amp charging in the future, you'll have to buy the separate Gen 2 MC, which only comes with a fixed NEAM 14-50 plug - so that could be a factor.

    If wires are not inside the wall, I'd strongly recommend conduit. It may even be code, but I didn't check. I used conduit for my receptacle.

    I wouldn't expect the install price to be much different using a NEMA plug vs HPWC- less than $100. You should insist on a NEMA receptacle that is rated for industrial use, not consumer. Consumer versions are designed for a few insertions over its life, such as a built-in range.
  • @Earl and Nagin - The OP didn't say where he lived, so I was just throwing it out there for consideration. I live in San Diego in a 40 year house with both a NEMA 10-30 electric dryer outlet and gas service in the garage. I did opt for the gas because, as you said, it is less expensive.
  • Sorry, I am in san jose bay area CA. So TeslaTap, do you recommend adding / changing existing sub for the new circuit and socket, or changing the breaker from the solar into smaller ones, and run wire off one new one, w/o adding changing panel?

    From Guy 1,
    "....<reason for hardwire only install vs receptacle> We would have to install a new sub panel as well, because GFCI breakers occupy the full slot in your outdoor main panel. With a regular breaker, we can install a 50/20 Quad type breaker that would power both the EV charger & your existing 20 Amp circuit in the panel." That's why he pushed for hardwire not receptacle only.

    Guy 2 didn't go into detail, I simply assumed I needed 2nd sub based on what I learned from first guy. If that's not right, then i can significantly change the job scope
  • @Teslatap, ahh got it...I missed the previous post with the main panel link.
  • @CAYorCYA ...from what I can see, you have an older 100 amp Main Panel (MP) that has solar feed of 2 pole 20 amps to the MP. The 100 amp 2 pole breaker in the MP feeds the Sub Panel (SP) you showed in an earlier post. Only a site visit and getting a complete overview of what is presently installed will allow a code compliant installation.
    1) Do a whole house load calculation to determine what your actual load is. IF you have GAS as your supply for ALL cooking, heating, hot water you might just squeak by with the existing 100 amp MP.

    2) If the load calc total is 65 amps or less, I would upgrade your SP to one that will accept more circuit breakers (CB), called a 48 circuit panel. { About $76.00 Internet #206705551 Model #BR1020H100FRNWV Store SKU #1001685824 } This model gets you close, but you do not need a main breaker, only "main lugs only" as the breaker in the MP is your over current protection device. No need to change out the existing cable running from MP to SP. You can then run a dedicated EVSE circuit to your charger.

    3) Pay your electrician and demand it be done with permits. That way, anything I might have missed will get covered by local codes.
  • @CAYorCYA ...Revised/extended comments.

    2) If your total load calculation is greater than 70 amp, I'd go with a new upgraded 200 amp Main Panel. That way you could install your EVSE from the MP. It also allows you (or any future owner) to change from gas appliances to electric. In the future, solar panels will supply more of household loads and getting free (after payback of initial installation) electricity for the entire home. Adding battery back-up will also allow you to use the free solar energy that folks with solar today are not allowed to use.
  • sorry, i thought I posted earlier but I didn't. The forum has a 2 step posting here that's a bit unfamiliar. Anyways. I actually have a 200A MP, there's a label that's about to fall apart that shows it. My contractor will move the 20A to new sub , put in a 100A, run the 100A to feed the new sub. New sub will host 20A from solar, and 50A 14-50, and 20A 110V socket, as well as comes with breakers (one of the RV outlet). And everything will be checked by city at the end. The cost is comparable to installing a HWPC from guy 1, but without the hwpc obviously. However, I am happy with the end result as I have flexibility.
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