<p>Every year my homeowner’s insurance company sends me a form asking me nosy questions about my home, and every year I set it aside and forget about it because I don’t know whether the electrical system is less than 100 amps or not. Does anybody know what would likely be the case for an ordinary house built in the 70s?</p>
<p>Just go add up the values of the circuit breakers. It’s almost certainly more than 100 amps. They range from 5 amps to 30 amps and there are certainly more than 20 circuits in a typical modern construction house.</p>
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<p>Not correct. </p>
<p>The sum of the circuit breakers does not necessarily equal the capacity of the box. </p>
<p>The box itself should have a label inside it identifying the total amperage. This is the total maximum draw for the whole house. The sum of the individual circuits can be greater than that amount, as you never max out all of your circuits. Or it could be less than that amount, if your system wasnt’ fully loaded when your house was built.</p>
<p>Look for the label on the handle of the main breaker, usually at the top of the box. I’m guessing you’ll have 100 in a 1970s house.</p>
<p>Electric range: 40 amp circuit breaker
Electric drier: 30 amp circuit breaker
Refridgerator: 15 amp circuit breaker
Microwave: 15 amp circuit breaker
Dishwasher: 15 - 20 amp circuit breaker
Compactor: 15 amp circuit breaker</p>
<p>Dedicated circuit are recommended or required by code for all of these appliances.</p>
<p>The national electrical code guidelines require a minimum 100 amp service. I don’t think you can even buy less than a 100 amp breaker panel anymore. Most residential construction is 100 amp to 200 amp.</p>
<p>It is true that you can’t get the exact capacity of the system by adding circuit breakers because you could have fewer breakers than the capacity of the box. However, you will quickly see that it is more than 100 amps.</p>
<p>The main breaker handle Dad o 2 refers to is probably a black bar that runs across multiple circuit breakers (mine connects four). This is the main circuit breaker.</p>
<p>The rating is also printed on the card on the door of the circuit breaker where you list what each circuit breaker does. My house was built in the 1980s and has a 200 amp box.</p>
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<p>Actually, the household service is generally much less than the sum of the individual breakers. </p>
<p>The main breaker limits the total current delivered to the individual circuit breakers in the box. The individual breakers limit the current that can be delivered through each individual circuits. </p>
<p>If you add the amperage of all of the individual circuits, it is probably 3 or 4 times the household service on the theory that you don’t run everything at once, and most circuits are drawing less current than the circuit is rated for. </p>
<p>If you were to run space heaters on each circuit, turn on all the lights, run the clothes drier, electric water heater, washing machine, garbage disposal, garage door opener, hair driers, table saws, etc., you might trip the main breaker, but I’ve never heard of it happening.</p>
<p>Thanks, everybody, for your replies. The circuit breaker box does not seem to have any numbers or labels on it anywhere, not even on the main switch, but I feel confident that I can check “no” and send in the form for once.</p>
<p>You definitely CANNOT add up amperage values on circuit breakers inside the box. Instead, check the main circuit breaker at the top of the box. The side of my main circuit breaker handle is stamped 200. (The sum of amperage values on circuit breakers inside the box is 630! Obviously they’re not all drawing maximum current at the same time.)</p>
<p>If your house has whole house heat and AC and range, oven , dryer, DW, clothes dryer, it would be likely to have 100 amps or more. Our previous home built in 1968 started with 100 amp service and it was upgraded to 200 with renovations.</p>
<p>Nearly every house I work on if it hasn’t already had renovations only has 100 amp service, but I’ve never seen less than 100 amps.</p>
<p>Here’s a site that tells you how to estimate your service without calling in an electrician: [Electrical</a> capacity or size: How to estimate the electrical service ampacity and service voltage entering a building by visual inspection and using a digital or analog multimeter or voltmeter - photographs and sketches of electrical equipment, panels](<a href=“http://www.inspect-ny.com/electric/ElecAmps.htm]Electrical”>http://www.inspect-ny.com/electric/ElecAmps.htm)</p>
<p>In my neighborhood there are still a few small, pre-WWII homes with as little as 40 amp service including some with post and tube wiring and screw-in fuses. Mine was one of them. When I remodeled I replaced and upgraded * everything * from the service drop in, using 125 amp service panel. After the building inspector signed off on my electrical permit my insurance agent filed a form and my homeowners annual premium dropped by over 30%.</p>
<p>With older homes that have had an electrical service upgrade in the past it is often difficult to know how many amps are coming into the box if the box was not changed.</p>
<p>Call your electric company and ask them while also telling them of your intention of doing the upgrade yourself. They’ll panic and send someone out (quickly). No joke. </p>
<p>Or, get an estimate from an independent electrician who will tell you. But never upgrade amperage service without getting a new box an and new breakers, (unless you’re MAcGyver.)</p>