Electrical Service 100 or 200 Amp

Old 03-23-04, 10:39 AM
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Electrical Service 100 or 200 Amp

You all have been so helpful in my basement remodel (passed inspection and am in the process of drywalling ) that I thought I would pick your brains on a question for my daughters soon-to-be new home. She is looking to buy a spec home and the standard electrical the builder installs is 100 Amp. This is a relatively small home (<1000 sf) with gas heat and gas water heat. But I suggested she upgrade to 200 amp just because it would be so much more expensive to do in the future should she need it. Cash is tight but it's only $200 more. Am I on the right track here or is 100 Amp OK for a smaller home?

Thanks in advance!!
Old 03-23-04, 10:54 AM
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To answer this question, you really need to do a 'load calculation'. Essentially you add up all of the electrical loads that would be in the house (lighting, kitchen appliance circuits, large appliances like ranges, space heaters, air conditioning, etc), scaled by loading factors which adjust for the fact that you don't use all of these circuits all of the time. At the end of the calculation, you end up with a Volt-Ampere quantity; divide by your service voltage, and you end up with the amperage required.

If you like 'DIY', then doing a load calculation is a great exercise. Rex Cauldwell's book 'Wiring a House' goes through a step by step load calculation; the NEC also has (a more difficult to understand) load calculation. Look for one of these books. Post here to get help working through the load calculation.

What you want to do is the load calculation for the current loads, and also a load calculation for 'everythng you can imagine running'. If with everything you can imagine running, you need less than 100A, then the 200A upgrade is _probably_ a waste.

Note that the 200A upgrade _may_ get you a larger panel; even when you only need 100A of electrical service, adding new branch circuits and having the flexibility to separate out loads may be easier with the physically larger panel. Of course, there is nothing that says that a 200A service comes with a panel that has more spaces It might simply get you thicker service wires and a 200A main breaker.


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