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Question DetailsAsked on 6/3/2016

Is it necessary to upgrade to 200 amp panel (which requires trenching) or just replace new 100 amp panel?

I have 1800 sq ft house built in 1960s (4 bdroom, 2 1/2 bath). Current electrical panel is 100 amps which needs replacing due to hazardous brand. Our original estimate was to replace and upgrade to 200 amp panel. Electrical company says this would require trenching (50 ft behind our house; 3 ft deep) to the electrical source which more than doubles our original estimate. We just found out we could replace the old 100 amp panel with a new 100 amp panel and avoid the trenching. Will 100 amp adequately service our home? There is no pool, no power tools. Cooktop, oven, clothes dryer, and water heater are gas connections. What would be the benefit of 200 amp? Trying to decide if it's worth the money and effort for the 200 amp or will the 100 amp serve our needs and address our safety concerns.

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Here are a couple of similar previous questions with answers FYI -

Whether you can depends on your local code - generally, when replacing a component with like size component (especially for a safety or recall replacement), you do NOT have to upgrade the system to current code unless it is deemed a life-safety issue. So - if your current load (as calculated by the electrician) exceeds the capacity of a 100A panel, then you will almost certainly be required (as part of the permit) to upgrade to adequate capacity.

I would check back with the power company (whoever you talked to - probably engineering) about HOW high an amperage you could go with without upgrading the service drop - might be 125, 150, or 175A panel/main breaker would work without that added trenching cost - and those type of upgrades would put you back into your expected cost range. Be sure to get in writing (eMail, etc) so you can provide it to your electrician - or just talk to him if he was the one who contacted the power company in the first place.

Be sure to check if they will require a larger meter base and meter too, or if they have the info on what its capacity is - typically less than the service drop wire capacity by about 20-25%, so the drop might be able to handle say 175-180A but the meter/base maybe only 140-150A. Depends on size and type of wire you have (most commonly probably 4/0 so wire should be able to carry around 250A if that size) - if they say can't carry 200A sounds like maybe 1/0 Aluminum URD direct burial type or maybe an old SE or RW-U type, which could be right if from the 60's.

Also ask if the service drop has to be upgraded for ANY amperage upgrade - because the reason for the upgrade may not be because it cannot carry the load, but rather because it may not have a neutral - many buried service drop wires back then only had the two live leads and a bare ground which was also used as neutral - not to code today. IF that is the case, generally (check with electrician) then ANY upgrade might require a new service drop so you might be stuck with the 100A service.

I would also talk to the electrician or the power company customer service about the charge - generally (not always) a service drop upgrade on the power company "side" of the meter is done by them at no charge - everything on "your side" of the meter is always your responsibility. However, some utilities do have the termination point at the transformer or distribution box at the power poles or street - but check because you might get this for free.

You could talk to your favorite realtor about the 100A issue - that is considered pretty minimal these days, especially for a 4 bedroom house - but if mostly gas appliances can work OK. In my area, 100A is the standard in 80's houses even with electric range and clothes dryer but gas water heater and furnace/boiler, so you might be fine. Whether not upgrading to higher capacity is likely to make the house less desireable to buyers a realtor can address. Certainly, if there is wiring already installed for electric range and clothes dryer and self-heating dishwasher, assuming a buyer might want them in electric should be considered in panel sizing and in your decision. Generally, if wired for electric range and dryer then those loads are supposed to be considered in panel and service sizing even if the current tenant/owner does not use them. If not so wired, they are not considered until someone wants to put them in.

One other possibility which I do recommend - upgrading the panel and the wiring and main breaker from the meter to 150 or 200A capacity is normally only going to cost an additional few hundred or so $ over 100A replacement if the panel is quite close to the meter (like basically behind the wall from it as it usually is), so I would do that regardless even if you don't upgrade the service drop capacity. Then the panel would have the rating for more circuits and higher amperage in the future if the service drop were upgraded by you or a buyer (or if a buyer madeit a contingency item for you to have done before closing) - you just leave a 100A main breaker in for now to limit the demand to what the wiring can handle for now but wire everything up to the meter for 200A capacity.

Technically, installing 150 to 200A capacity house service equipment will make your installation marginally safer - really no difference if the breaker works correctly at 100A demand, but if it fails to trip or allows an overdraw then an oversized system is safer, though not something that would normally be a decision-making factor.

I am guessing you will find maybe you can upgrade to 125 or 150A panel and main breaker without upgrading the service drop - but early 60's is when capacities were going from 50 or 75 or 80A up to 100 or 125A - so it is possible 100A is the wiring capacity.

Answered 4 years ago by LCD

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