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I recently purchased a mobile home with a large workshop and 2 car garage. The panel inside the home is 100 amps. The outside panel has 100 amps at the meter. In the outside panel there is 100 amp breaker for the home along with 2 other breakers a 60 amp to the workshop and 40 amp to the garage.

All three buildings are drawing continuously with water pump and outside lights at night. My outside breaker has tripped several time when the furnace and the clothes dryer are running. My power bill was over $500 this month. Am I drawing too many amps?

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    Is the furnace a natural gas/propane/oil furnace with electric controls/blower? Or is an electric furnace (aka really big toaster)? That can draw a ton of power. Also, is your hot water gas/oil or electric? – manassehkatz-Moving 2 Codidact Jan 28 at 16:17
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    Is this a sudden increase in your electric bill? "Recently" doesn't tell us how many bills you've had to pay in the past - this could be the very first one, and it's hard to make an assessment on only 1 data point. – FreeMan Jan 28 at 17:16
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    It's not clear what you're asking. Too many amps for what? Yes, your bill seems large, but how would we know if it's unreasonable? – isherwood Jan 28 at 17:41
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    I can't vote to close bc the OP is asking a fairly detailed question in the nature of "what's going on here"? Additional information would enable us to better answer the question. Also, the location is important to know the electric rates. Parts of California is up to 40 cents, per KW, while here in the NW it's about 12 cents. Big difference. manassehkatz asked great questions and if answered, we can better help. – George Anderson Jan 28 at 23:19
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    Yes, what are you using to heat the place? – ThreePhaseEel Jan 29 at 0:13
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Yes. Given your service and power demands, the fact you are tripping your main breaker meaning it's doing it's job properly, and your high power bills, so YES, you are overloading your service/system. I presume your furnace is electric resistance as well as your clothes dryer. If so, and you want to stay "all electric" you are going to have to upgrade your main panel to 200 amps. If you have gas available, changing to a gas furnace and/or clothes dryer could possibly avoid the necessity of replacing the main panel. Its rare for a main breaker to trip, so again, YES you're drawing too much power. If you don't upgrade, the only thing you can do is time your energy consumption, like turning off the furnace when running the dryer. If you have an electric water heater, you might have to turn it off at times as well.

EDIT: If you have natural gas available, it's almost always a LOT less expensive than all electric. If not, propane is another option, but, depending upon where you are and current prices vs. electric, may not save a lot of money on ongoing utility costs.

Checking on your amount of insulation, air leaks and if possible upgrading the insulation and sealing air leaks could minimize your power usage. But for what you've got going on now, Yeah, you are overloading your service.

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That seems a large monthly cost for a mobile home.

You need to investigate what is using all your power - could be any of:

  • a bad appliance running all the time, like an oven left on or a freezer with damaged insulation
  • The workshop has high-draw devices like welders left running continuously,
  • an intermittent short, which is a high fire risk
  • your neighbour's running all their stuff off your supply too, with a creative tap-off somewhere
  • Your heater/cooler are running hard but bad insulation means it leaks heat in/out.

A small plug-in unit like a "kill-a-watt" power meter can help measure specific appliances with normal plugs, but a clamp meter is needed around a single phase/active wire to measure a circuit. These cost a bit more but can show the current draw in the wire to the garage and to the workshop.

enter image description here A clamp meter in use, around a single phase wire (not around a neutral as well)

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    The clamp meter only works if you can isolate one wire; then it works well. Running the entire cord through the clamp will read zero (or close to), regardless of what's actually happening. – AaronD Jan 29 at 12:45
  • @AaronD concur - I said "clamp meter is needed around a phase/active wire to measure a circuit." which is slightly ambiguous. Edited now - remember you can edit posts as well. – Criggie Jan 29 at 21:22
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The fitness of a service is decided by a load calculation

This is a calculation which tallies each load, allowing for certain load factors. Typically these calculations are done in VA, which is volts * amps (as you might guess).

For instance, all general receptacle loads are figured at 3 VA per square foot of the house. Kitchen and laundry room circuits count as 1500 VA each. Electric ranges have some fairly complicated math so they work out to less than you'd expect. A dryer is typically penciled in at 5500 VA (pretty close to accurate). And you ignore either the furnace or air conditioner, depending on which is lower.

The problem is, you have resistive electric heat

And you really need to talk to the electric company and see if they have a rate structure appropriate for someone like you.

Because generally there are only 2 reasons someone would install plain electric heat like this: a) the power company offers a favorable rate structure which encourages it... or b) the house builder was very, very cheap and made the house $1500 cheaper by choosing heating tech that would stick you with a $500/month electric bill.

enter image description here

To give you an idea just how cheap electric heat is to build... consider this Cadet 2000W / 6800 BTU/hr baseboard heater which sells for $58. It's not cheap like Chinese; it's a perfectly high quality unit that will run for 30 years. One #12 cable can power 2 of them. Zoned heat, no exhaust... it's beautiful. The problem is, it costs 25 cents an hour to run at normal energy prices... running 1/3 of the time, that's $60/month per unit, and you'd have 1-2 per room!

The other problem with electric heat is you use a LOT of it, and that is a big load on the panel.

Honestly, an "all-electric house" (dryer, range, water heater, A/C) without electric heating pretty much maxes out a 100A panel. With electric heating, forget about it!

You need to convert to either heat pump or gas

It may be time to get a propane tank and install a gas furnace.

One option is go with a whole-house heat pump, which doesn't "make heat the hard way", it steals the heat from outdoors. It's like an air conditioner in "reverse"; it makes your house warmer by making the outside colder. It's also an air conditioner in "forward" - heat pump systems also work as air conditioning systems. Two birds with one stone. Because it's only pumping heat, it uses a great deal less electricity. However, it does not work at all if the outside is too cold -- so you need something as a backup. Which is back to straight electric heaters.

So it's ironic, even though heat pumps don't require 200A service, the fact that they need heat-strip emergency heat means you need 200A service after all.

A friend of mine lives in a truly all electric house: Water heater, range, dryer and a heat pump system. It takes a 400 amp service because the emergency heat is 140 amps all by itself.

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    The good news is that mini-split heat pumps these days have enough "oomph" to be a sole heat source in many parts of the USA, especially if you're good at installing/retrofitting envelope details so that the heat you've worked so hard to pump into the house stays in the house instead of flying right out with the next draft – ThreePhaseEel Jan 29 at 4:19
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    Harp!....dude, you don't know that. The OP never responded with what sort of heating system he has. For all we know he could be running a bunch of grow lights for a marijuana grow or organic vegetable grow in one of the outbuildings. They take a lot of power. – George Anderson Jan 29 at 5:16
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    @George from the symptom, the main breaker tripping when the heat is on. – Harper - Reinstate Monica Jan 29 at 5:37
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    @GeorgeAnderson You are 100% correct. But I think Harper's intuition is right on this one - and (as you know) I suggested as much in my initial comment on the question. Plus, I suspect a key is mobile home. While I know they can be heated with gas, I wouldn't be surprised if a lot of them are designed all-electric so that there is one less thing (and a dangerous one if not done perfectly) to connect when they get moved around. – manassehkatz-Moving 2 Codidact Jan 29 at 6:08
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    I dk if insulation can be added to a mobile, maybe just upgrading the windows could help, but that's expensive. Harp: good catch on "when the furnace is running" + But I'd still like to know for sure what his furnace is. My parents in laws lived in a mobile with a heat pump. A mini split would probably be ideal. Upgrading the service to 200 amps would leave him stuck with an ongoing $500/mo power bill, which will most likely keep going up. I think the better investment would be to improve his energy efficiency. – George Anderson Jan 29 at 16:08

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