How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
What is the right size electric panel for a house?
Friday, October 19, 2018
Although most people ask about the size of their electric panel, what electricians evaluate is the size of the “service.” The service is defined in amps (short for amperes), which is a measure of electrical current-carrying capacity; in other words, how much electrical power is available through the main service panel.
In a modern home, the service size is easy to determine: you look for the large switch located either at the top or bottom of the panel and separated from the two rows of other switches (circuit breakers). It will have a number on the side of the switch or very close to it--typically 100, 125, 150, or 200. This is the rating of the electrical service to the home in amps.
While it may appear that 200-amp service is “better” than 100-amp service, that is not exactly true. The 200-amp service is simply larger. If the electric appliances in the home don’t require the additional current, then all that extra capacity is unnecessary.
The minimum size electric service today is 100 amps. If your panel looks like the one in the picture above, with screw-in type fuses, then you likely have a 60-amp service. While pre-WWII 60-amp service may be adequate for a small home with a gas range, water heater, and furnace, it is problematic for homeowners insurance. No insurance company will insure a home with 60-amp service, and many will not insure a home with even 100-amp service if the panel is a screw-in fuse type.
The question we are often asked when explaining the insurance issue facing homes with older fuse-panels is this: “But the current owner has insurance. Why can’t we just go with their company after we buy the house?” The difference is that insurance companies are slow check up on current policy-holders and require them to upgrade but, when issuing a policy to a new owner, they want the home to meet their latest minimum standards.
When a home is first built, the designer calculates the required size electric service based on the square footage and electric appliances planned. Electricity usage has been growing at a rate of approximately 5% per year for a while now and, as TVs keep getting bigger and kitchens fill up with more and more counter-top appliances, the trend is likely to continue, even in this era of fluorescent light bulbs and Energy-Star ratings.
So a healthy size electric service is a good idea. But 200-amp service is not necessarily the gold-standard for homes, even today. For a small home or condo, 125 amps is adequate; and 150 amps is quite satisfactory for many average size family homes, especially if they have any gas-powered major appliances.
If we feel that the size of the electric service is questionable during a home inspection, we will recommend that a licensed electrician calculate the estimated loads in the home and advise if a service upgrade is recommended. More often than not, though, they will say that the service in an older home--dating back to about the mid-1960s--is still adequate.
Also, see our blog post Who is the manufacturer of those "bad" electric panels?
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