I am a new townhouse owner and and hoping to get some help from experts here to understand my breaker panel, specifically

  1. What is the total amperage service to my unit.
  2. How much capacity is currently used by breakers already installed and how much is free.
  3. Can I add an air-handler and / or a tank water heater to it without upgrading? What is the general process by which I can determine this for any device? What is the key piece of information that determines this?

I did talk to couple of contractors but didn't get satisfactory answer.I tried to read about it over the internet but I have failed to apply those learnings to my situation.

I have attached pictures of my panel and main panel.


Panel door

Main breaker

Edit: Adding some more details:

Better image of the panel

enter image description here enter image description here

Other details: 1600 Sq feet livable area (1900 including basement) Cooking on gas all other appliances electric Currently have 3 ton gas furnace and 3 ton AC

  • 1
    Can you post a photo showing the labeling down the left side of the breaker panel please? Jan 8, 2020 at 12:38
  • Also, how many square feet is this townhome, and can you post photos of the nameplate for the A/C please? Jan 9, 2020 at 0:25
  • @ThreePhaseEel thanks edited the post, also can you please elaborate what is 'nameplate for the A/C'?
    – Suyog
    Jan 9, 2020 at 7:21
  • The metal plate on the air conditioner compressor that has the part number, UL/... labeling, and so on on it... Jan 9, 2020 at 12:44
  • Also, what's the nearest city to where you're located, and how is that new air handler going to supply heat? Jan 11, 2020 at 0:28

3 Answers 3


Don't get electrical advice from plumbers.

Quite possibly

When you calculate the burden the loads place on the panel, that is called provisioning. You don't provision every circuit for its breaker trip value, but rather for a lower number that reflects the probability of it being active at the same time as other loads.

A typically reasonably-electric home with a 100A main can have a 30A air conditioner, a 30A dryer, and a 30A water heater, and even a 40A range with no trouble.

I see a 30A air conditioner and a 30A ??? that ends with "r". Not water heater, clearly, and 30A is too small for a range, so it must be a dryer.

The rest of the breakers (even the other 2-pole breaker) look like lighting and receptacle loads. Those provision very lightly, since it's assumed you're not heavily loading them all at the same time. Also they are 120V loads so they only are half the apparent burden.

You have to crunch the numbers according to NEC's procedure (here's a worksheet the City of Carmel uses), but I see lots of headroom in this panel, ampwise. Spacewise is another thing; this is extremely overstuffed (which is trouble if you want to add anything), and every breaker is the wrong kind.

That panel is OK, the breakers gotta go.

This is a Challenger type C panel. The panel is perfectly fine. However the breakers are known firestarters just like Zinsco and FPE, except those panels are bad too. Your panel is perfectly fine, but the breakers all need replacing. Fortunately this isn't prohibitive.

Further, the lower left is a Square D breaker which is an alien breaker - a breaker not made for this panel, and a physical misfit. The problem is where the clip grabs onto the bus stab - they are mismatched, and make point contact instead of surface contact. They can arc and burn the bus bars.

The fool may have installed a Square D breaker on the logic that Challenger Type C breakers are unobtanium. Untrue. By happy accident, the Eaton BR line is cross-listed Type C (because BRyant bought Challenger and fixed their breakers, then Eaton bought Bryant.) This is possibly the most common breaker in the US.

enter image description here

Sold at any hardware store for $5. $10 for the double-stuff breakers you need.

For that split 15/20A double-stuff breaker, look for an Eaton BR1520. It's a bit hard to find. For the GFCI or AFCI or whatever breaker, just get both protections in one breaker, it's not much more money. Get something like a BRAFGF115CS which is a dual-function AFCI+GFCI breaker for $50. This has indicator lights to tell you why it tripped, unlike the annoying Square D.

Heat pump

I hear you talking about a heat pump, but presumably that will replace the A/C. So that is already factored into the system, and you don't need to provision any more power for it than you already have for the A/C.

Now, heat pumps often have "emergency heat" for when the ambient air is simply too cold for the heat pump to work, and these can pull as much as baseboard electric heat. However, presuming you are located in metro California, you don't encounter anything below 25F. It's pretty easy finding heat pumps capable of working that low. Alternately if you can get by with only 30A of emergency heat, it can share the breaker because it doesn't run at the same time as the heat pump.

Given that you're in PG&E territory, I strongly recommend you install an "emergency heat" in the form of an Empire style gas furnace - either floor or wall. These units do not need electricity. So you're not stuck like the poor shlups in the Northeast, having to fetch fuel for a generator simply to get their furnace's electronics and fluid handler to power up. With an Empire furnace and gas water heat, making your home perfectly livable becomes within easy reach of a homebrew or commercial PowerWall type solution.

  • This was very very informative, thanks a ton! Yup thing with 30A is dryer, I will add better picture.I will start looking into breaker replacement and auxiliary heat.
    – Suyog
    Jan 9, 2020 at 7:06

It looks like you have a 100 amp service.

You cannot figure out what the load is by adding breakers. I am glad you don’t have stab lock breakers I think.

Can you add an air handler? Maybe, possibly what size is it???

Can you add a water heater ? Possibly most require a minimum of 30 amps some up to 125 that I have installed in that case not without an upgrade.

You have talked to several contractors and you ask us on the web with a couple of pictures ????

From the PG&E listing on the meter I would guess you are in California or there service area.

What do you hope to answer that a professional(s) did not? Can you add more information? more info is needed , but how do you think someone on the web can help when you have had multiple pro’s there ?

  • Thanks! I did not have contractors over yet., I just shared same pictures with them and talked over the phone. Both HVAC and Plumber guys said said that I do have enough capacity to add air-handler and tank water heater but that puts my panel to 70% of load and I need to take these to city to see if new load calculations won't overload the panel. Intention of this post is to learn how they estimated this number and mainly to see what are the right questions to ask them or to city person. Air handler is 3 - 3.5 ton.
    – Suyog
    Jan 8, 2020 at 7:59
  • This info helps, 3.5 ton air handler sounds like a heat pump or AC unit probably less than 40 amps, again it matters if you have gas or electric heat as code can allow for example a 80 amp heat and a 80 amp air conditioner because they are not used at the same time (ok that is crazy large for ac) but a air handler usually is just a few amps (15) could be possible. Next a tanked water heater 30 amps is possible but if you have gas heat now the cost to go electric will be crazy high , I am an electrician and after installing 400 amp services to support electric on demand would not recomend
    – Ed Beal
    Jan 8, 2020 at 8:17
  • Thanks much for your suggestions, I would drop electrical water heater and stick with gas. Yup 3 ton air handler would be paired with a heat pump if I decide to go that route.
    – Suyog
    Jan 8, 2020 at 8:19
  • 1
    Note current code allows the feeder to be sized at 83% of the main breaker , but we don’t add breakers to figure what the load is , the basic load is 3 va per square foot 1500 va each for 2 kitchen small appliance circuits and 1500 va for a laundry circuit. Next add water heater if electric , dryer again if electric, range and stove again if electric so you can see an all electric home can use hundreds of amps so much more info is needed.
    – Ed Beal
    Jan 8, 2020 at 8:26
  • I do recommend gas on demand gas water heaters I have installed in 2 homes and loved them, great to fill my hot tub at 105f can’t do that with an electric 3 bath home we never ran out of hot water but it takes a large unit to support multiple loads , ok without a 400 amp service probably not possible with electric. You may be able to add the heat pump, I have several in my current home but if I had gas I would install a high efficiency furnace if the duct work was there if not mini splits or heat pump/ac units in each room is the way to go.
    – Ed Beal
    Jan 8, 2020 at 8:38
  1. You have a 100A service, based on breaker below meter.
  2. The minimum size allowed is complicated formula from the NEC, there are online worksheets.
  3. Some jurisdictions make you recalculate when you apply for a permit to add load, it's a local policy issue.
  • 1
    I agree with the 100 amp but can I add a tankless? Who knows what the op wants but I would say NO! A 100 amp service is the minimum not complicated at all. Much of the PG&E service area has gas or the areas I worked in, but if all electric no way on a 100 amp service. Even today a 100 amp service is the minimum but the square footage of the home is needed and if gas is available affects the requirements.
    – Ed Beal
    Jan 8, 2020 at 7:53
  • @EdBeal as I said I am not considering tankless (it was made very clear to me on call that is no-go). I was exploring with-tank electrical heater. Yes I do have gas available and my 15 year old water-heater I am replacing currently runs on gas. Total area is about 1600 excluding basement.
    – Suyog
    Jan 8, 2020 at 8:16
  • 2
    For your water heater electricity will be significantly more expensive than gas. I don't know your exact pricing, but NG with 80% water heater @$1.00 per therm and electricity at $0.13 per kwh the difference is 3x the cost. Search for heatcalc.xls on the net for a spreadsheet you can download and customize your costs. Jan 8, 2020 at 13:48
  • 1
    The recovery rate is also slower and with the new high efficiency water heaters the recovery is even slower, you should check PG&E may have rebates my power company had a program last year that the new high efficiency water heater only cost 15$ if you went with a 40 gallon the larger sizes cost more I think it saved us 450 for just filling out a form.
    – Ed Beal
    Jan 8, 2020 at 19:43
  • heatcalc.xls is amazing! Yup PG&E has $300 rebate on heat-pump water heater I was looking at earlier, anyway dropping electric water heat for now though
    – Suyog
    Jan 9, 2020 at 7:23

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