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100 or 200 Amp Electrical Service?

200 Amp Electrical Panel

200 Amp Electrical Panel

Is the 200 Amp service worth the extra expense?

One of the most frequent questions the new home buyers ask is whether to get 100 or 200 Amp service for their new home. 

If you don’t have any 220-volt electricity hogs, such as electric heat, hot water tank, dryer, range or central AC a 100 amp service for a modest size home will serve most families. But this is the minimum service size allowed by the National Electrical Code, and you leave little room for future expansion.

100 or 200 Amp Electrical Service?

Adding 30% to the cost now may seem large, but if the time comes when you can’t do with 100 amps, replacing your new 100 amp service with a 200 amp service increases the price by approximately 30%.

We have added a detailed calculation sheet at the end of this article, but the following is the way to calculate your load:

The National Electrical Code uses Volt-Amperes (VA) in calculations, but for a residence you can use Watts and be so close it doesn’t matter.

Here is how you can get an estimate of your load.

3 Watts per square foot for lighting and general outlets; say 7500 for a 2500 square foot house.

Now add electric dryer (5500), electric water heater (4500), electric stove or cooktop + oven (8500), two kitchen appliance outlets at 1500 (3000), laundry outlet (1500), two tons of air conditioning (3000 watts). Let’s add 6000 watts for your shop (6000). You probably aren’t running your welder and your saw at the same time.

Total is about 39,500 Watts or Volt-Amperes. We are going to round it up to 40,000 to make the calculations easier.

Now all of those things are not operating at one time, so the NEC lets you take 100% of the first 10,000 Volt-amperes, and 40% of the balance. So you have 10,000 + 0.4 x 30,000 = 10,000 + 12,000 = 22,000 Volt Amperes.

Now 22,000 VA/ 240 Volts = 91.7 Amps, say 92 Amps.

It is good practice to have 25% margin, and 125% of 92 Amps = 115 Amps. THAT IS YOUR LOAD, for the assumptions that we made. You may not have an electric water heater or electric dryer.

You are limited to 42 breakers/circuits in a panel. A large 2-pole breaker to a sub panel counts as two circuits. A tandem breaker (two breakers in one slot) is two circuits. You DON’T add the circuits in the main and the sub panel.

You want to balance your loads. The 240 Volt loads on 2-pole breakers are automatically balanced. It is very hard to create unbalanced loads because breakers that are one-above-the-other on the same side of the panel are on opposite poles of the service. The easiest way to create an unbalance is to use large tandem 115 Volt breakers. Stay away from tandem 30 amp breakers.

Another thought to consider, when selling the house some day you may find it an easier sell, and may make back your 30% and then some, with an attractive feature like a 200 amp service. One thing home shoppers don’t like to think about is the possibility of having to mess with the electrical system.

Calculate Electrical Load Worksheet Download!

8 Comments
  1. Hey, great article on the differences between 100 and 200 Amp.

    Lilly Jones | http://www.copperheadelectric.ca/

  2. Service load calculations 3va per sq ft according to nec sq ft/240v
    Adding appliances @ 1500va each stoves 8 or12 kw and dryer at 5000va
    Water heater 4500va total the load
    Sizes the service for a single family dwelling

  3. Really great info 100 or 200 amp service. Thanks!

  4. How much does it cost in Ontario to go from 100 to say 125 Circuit

  5. Will there be a difference in monthly Hydro One charges?

  6. Families today tend to need much more electrical power than previous generations. As technology grows, so does the load on domestic electrical systems, which results in the need for an electrical panel upgrade in many older properties.

  7. I recently came across your article on 100-amp or 200-amp service and wanted to share my appreciation for the valuable information you provided.

    Your article does an excellent job of explaining the differences between a 100-amp and a 200-amp electrical service and the factors to consider when choosing the appropriate service for a residential property. The detailed breakdown of the electrical requirements and load calculations helps readers understand the capacity and capabilities of each service.

    I particularly appreciate how you highlighted the importance of assessing the electrical needs of a home and considering future expansions or upgrades. The information you provided on the benefits of a 200-amp service, such as increased capacity and flexibility, is valuable for homeowners who may be contemplating electrical system upgrades.

    Additionally, your article discusses the role of a qualified electrician in assessing and determining the appropriate service size based on the specific requirements of a property. This emphasis on professional expertise underscores the importance of consulting with a licensed electrician to ensure the electrical system meets safety and functionality standards.

    The inclusion of common appliances and their electrical demands as examples helps readers visualize the electrical load and better understand the implications of choosing a 100-amp or 200-amp service.

    Overall, your article provides a comprehensive overview of the factors involved in deciding between a 100-amp or 200-amp service, enabling homeowners to make informed decisions about their electrical needs.

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