My panel has a 15-amp breaker for two-bathroom outlets and two outdoor outlets. Is that normal? I would like to replace that with a 20 amp breaker. Also, I want to replace my water boiler with the "Ecosmart ECO 36 - 36kw 240V 150A Electric Tankless Water Heater" but that requires 4 x 40 amp breakers (my electrical panel is 200 amps).

So I'm trying to make room for it on my electrical panel by replacing the quad breaker with a single-pole tandem 20 amp breaker since the water boiler won't need the quad breaker anymore. Is all of that possible and correct to do?

In the future, I will remove the furnace and replace it with an all-in-one heat pump, perhaps some of the furnace breaker slots will be freed up.

Another thing to note is that my refrigerator and microwave are on the same line and when the toaster and microwave get used the microwave power dims a bit. My microwave keeps dying every few years. Perhaps the fridge and microwave should be on their own breaker, right now it feels like too many things are competing for power on that line/breaker. My electrical panel is exactly the way the electrician left it when the home was made in 2006, except for the labels.

My Electrical Panel - Replace Breakers.

Eaton Cutler-Hammer Single-Pole BR Type Circuit Breaker, 20-Amp, 120-240-Volt.

Cutler-Hammer BD2020 Type BD Circuit Breaker, 120 VAC, 20 A, 10 kA, 1 Pole, Thermal Magnetic Trip.

My Electrical Panel.

My Electrical Panel - 200 Amps.

  • 3
    You can't change the bathroom breaker to a 20 Amp unless you verify that the wire connected to that breaker is #12 AWG CU or #10 AWG AL.
    – JACK
    Jun 25, 2020 at 18:30
  • 3
    The single 15A breaker feeding outlets in even one bathroom is substandard by current code, which requires a 20A breaker for that purpose. I think it can be shared across bathrooms, though that's not a great idea depending on loads (hairdryers, etc.) Normal for the time, perhaps, since it seems to be "lumping all the GFCI loads on one breaker" for an era before the loads for bathrooms were increased and the places GFCIs were needed were increased.
    – Ecnerwal
    Jun 25, 2020 at 19:00
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    This is way too many questions in one Q. Jun 25, 2020 at 22:50
  • 2
    What problem are you trying to solve by replacing your existing water heater with a tankless unit? Jun 26, 2020 at 3:05
  • 1
    @j... you have not installed many electric on demand water heaters, in my answer I provided an example of a residence that the owner wanted to go to on demand electric , an all electric home this usually requires a 320a continuous panel or a 30/40, 150 for the wh and 120 for the furnace and you are at 170 amps turn the oven on and 1 surface element and with normal lighting we are over 300a I have installed a few of these and some smaller ones in the 90 amp range the smaller required point of use in the bathrooms 30 amps each for those because pressure fluctuations affect tankless temps.
    – Ed Beal
    Jun 26, 2020 at 19:29

5 Answers 5


I would SERIOUSLY reconsider an on demand, tankless electric water heater. All the hype about the tankless: IE: Why keep 50+ gallons of water hot all the time when you don't use it? Well, once the water is heated it pretty much stays heated given the quality of the insulation on electric water heaters these days. While tankless gas WH might make some sense (I still don't like them), a tankless electric WH is a MAJOR POWER DRAW and more complicated than a tank type.

I don't think you'll ever get cost recovery on the small energy savings you might get from a tankless. Have you considered a HP water heater? I don't know a lot about them, but they operate on a heat pump principle. I hear their recover time is very slow, but there are real energy savings there.

  • Heat pumps are mandated for electric in my county but the utility had a rebate that paid all but a few bucks, the only problem I see if they are inside the home the cold air is discharged in the “closet” requiring that space to be heated, it would be nice if they vented to the outside. I have had tankless gas and additional point of use electric and thought that was the best combination and it worked well with a 3 bathroom home.
    – Ed Beal
    Jun 25, 2020 at 19:55
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    @Harper-ReinstateMonica Agreed: It's like trading one problem for another. Jun 25, 2020 at 23:07
  • 3
    I know this is a US context but in the U.K., tankless boilers (known as combi boilers) are generally considered to be the better option. One of the main benefits is you never run out of hot water.
    – Tim
    Jun 26, 2020 at 7:59
  • 1
    It's not a saving issued but more of a space issue. The tankless can be put on the wall and it's 17 by 19 and under 5" thick. We have a very small utility room and would like that space for something like a linen closet. We're currently making home improvements and upgrades. I guess my current electrical panel should be dumped and replaced by a newer one that is more properly wired, I just hope it doesn't cost me more than $2,500 or go way over budget.
    – AngelD213
    Jun 26, 2020 at 11:05
  • 1
    Who heats up domestic HW to 80C? That's dangerously hot for DHW. Here in the US a typical setting is closer to 50C. Yeah, somebody is probably going to pop off about legionnaires disease, but fact is about 50C is a common setting. Jun 26, 2020 at 16:56

First NO you cannot just change breaker sizes.

Second is your panel even rated for tandem or double stuff breakers?

And last ARE YOU KIDDING? You want to put a 150 amp water heater on a 200 amp service, do you plan on turning all the lights off unplugging the refrigerator and freezer so you can cook dinner on the range? Also make sure the dryer and furnace is off.

No your service is not even close to large enough to put that water heater in.

You will need a 30/40 panel at least some call a 320/400 panel.

From experience you should first find someone with a similar model. I have upgraded a customers service installed a similar sized unit, then added point of use kitchen and bath and the home owner was not happy / upset and had me return the system to a tanked system after almost 20k spent.

You would not be able to get a permit with the existing service panel.

  • Approaching the Green Acres electrical system! LOL Jun 25, 2020 at 19:37
  • That panel looks acceptable as is for current loads, Ed Beal: Would it be possible (IE code legal) for the OP to simply add a 2nd 200 amp panel and upgrade the meter base to a class 320 service? Or would he get tied up with a lot of other upgrades (AFCI, GFCI, etc.) EDIT: POCO would have to verify feed wires could support class 320, I would bet. Jun 26, 2020 at 15:30
  • That would be 2 service panels it can not be done without having a disconnect at the meter, but that is code once the 2020 code is accepted by the jurisdiction. The existing panel probably has mixed grounds& neutrals and this would have to be changed so it could be done but with all the required changes i would replace The panel.
    – Ed Beal
    Jun 26, 2020 at 16:25

Well done with all the pics! You'd be amazed how many people don't think of that.

NO! You cannot simply replace a 15 amp breaker with a 20 amp breaker unless... ALL the wiring protected by that breaker is 12AWG. If there is any 14AWG wire anywhere in the circuit, you're creating a fire hazard. 14AWG isn't designed to handle 20 amps

  • 4X40A 2-pole (240V) breakers = 8 spaces. There are only 5 spaces free.
    – Ecnerwal
    Jun 25, 2020 at 18:34
  • @Ecnerwal I think the OP stated 4 - 40 Amp breakers but that does seem low.
    – JACK
    Jun 25, 2020 at 18:42
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    The OP also stated that is was a "36KW 240V 150A" heater. So 160A at 240V (8 spaces) is plausible while 80A at 240V or 160A at 120V (4 spaces) is not. Frankly, I doubt this is feasible at all - turn on the range while running the dishwasher, perhaps the dryer, and manage to get a main trip on the 200A feed. A 150A water heater is one heck of a load when it's on, and I really doubt that the rest of the house will be consistently happy on the 40 or 50 A left over.
    – Ecnerwal
    Jun 25, 2020 at 18:50
  • We also have to remember that resistance heaters are limited to 48a on a 60 amp breaker or multiples as it sounds like the MFG has specified. NEC 424.22
    – Ed Beal
    Jun 25, 2020 at 19:35
  • 1
    I guess I should get a new electrical panel to allow those things and hive the microwave/refrigerator with their own dedicated breakers and also upgrade the service to 300/400 amps for future-proofing the addition of a future central heat pump. I'm no expert on this stuff and it is at times confusing, so I thank you for responding in a non-mocking way.
    – AngelD213
    Jun 26, 2020 at 10:55

I agree with the responses you received, you can’t exchange a 15amp breaker for a 20amp without changing the wire size to #12. In regards to changing the entire panel....the size of the wire feeding the new panel will have to be increased to handle the potential load of the new panel. In my area microwaves, refrigerators, and dishwashers all require a dedicated 20amp circuit. I also agree that tankless water heaters are too expensive, the payback/break even time is too long. Standard water heaters are pretty efficient, just check that they aren’t set too high. Good luck.


I'm adding another "answer" to be sure to consider flow rate. My son decided to use a tankless water heater (fairly large one), but didn't consider flow rates needed. I was showing the house to a builder friend of mine and he spotted the fancy, multi head, high flow rate shower in the MB and then noticed the tankless. Took a look at the tankless and he said, no way can that support the flow rate needed for the shower. So after discussions with the plumber decided to add a SECOND tankless WH!

So please consider the flow rate needed and that your tankless can support it.

  • 1
    Even without a high flow shower for maximum efficiency with tankless units the temp is supposed to be set to the temp Water being used. This water doesn’t take as long to get to the point of use because the hot tap is almost full open. then there is the need for hot water in the kitchen point of use to bring the temp up for the sink and dishwasher. In 3 bathroom homes someone was always using water while someone was in the shower so you crank the temp up or add additional point of use tankless heaters because tankless do ok with a constant flow but fluctuate when the demand varies.
    – Ed Beal
    Jun 26, 2020 at 19:40
  • I also think they don't play well with HW re-circ systems. Wouldn't they cycle a lot? I have an indirect water heater (tank) with re-circ. It's so nice to get HW within 3 seconds at every faucet in the house. Jun 26, 2020 at 20:00
  • That can be overcome but then you turn your plumbing into a storage system kind of defeats the tankless idea.
    – Ed Beal
    Jun 26, 2020 at 20:47
  • @EdBeal Agreed, But I have an in-floor hydronic heating system that is the major load on the 2 boilers. The indirect heat water heater is kinda a byproduct of that system. The system is plumbed so that if there is a call for DHW heating only part of the system comes on...basically a circ pump between the boilers and the indirect water heater. When there is a call for DHW the boiler (usually just one) runs for quite a while at a lower temp so I get good condensation efficiency and it doesn't short cycle. Jun 26, 2020 at 22:58
  • To tell the truth a heat pump boiler makes the most sense for a hydronic system The problem with most heat pumps there efficiency drops off at freezing when you need it most I think ours works into the teens , but then wood or pellet is more economical in the Pacific Northwest.
    – Ed Beal
    Jun 27, 2020 at 0:19

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