This is one of my favorite subjects in our field of work. The residential electrical industry has changed so much over the past 2 decades. If you went back in time even just 25 years, a 100amp electrical service was enough for the average single family home. And if you were lucky enough to have a 200amp electrical service? You never would have thought outgrowing it would even be a possibility!
But these days, things are certainly changing with electrical vehicle chargers, A/C systems, electric heat pumps, electric water heaters, floor heat, driveway heat, ductless air systems. I could go on!. There are MORE electric appliances than ever, and we don’t see that changing. I believe that as solar power and battery backup systems (such as the Tesla Power Wall) become more affordable, homeowners will be switching out all of their gas powered appliances for electric. Even heat and hot water. It makes sense doesn’t it? If you have a solid solar array that is producing a good bit of electricity why not take advantage of it? If you happen to have a battery backup system too, even better!
So what does this all mean for our homes electrical future? To me it pretty much means the thought of installing a 100amp service on any single family house is completely out of the question. The 200amp electrical service has become the base, the bare minimum in my eyes and i see many customers going even larger.
How about the cost of a 100amp vs 200amp?
Something else to keep in mind while picking an electrical service size is the labor to install it. Guess what? The actual installation of a 100amp service is pretty much identical to installing a 200amp service. Well besides working with a slightly larger wire. So what does this mean? Yup you guessed it, the labor to install a 100amp service will be nearly identical to that of a 200amp. So which one is a better investment? So you must be thinking, well the material must be a lot more right? Well it depends what your definition of “a lot” is. The delta between the two on average is around $400.00 to $500.00. So no, not a huge difference. I should also mention that if you ever decide to sell you home, potential buyers (and their home inspector!) will LOVE that your home has a 200amp service.
I must mention that once you get up to a 400amp size, it does get much more expensive. Not only is the equipment more heavy duty and expensive, but it’s heavier and harder to work with. This leads to increased labor and material costs. Making the jump to a 400amp service is a big decision and a qualified electrician should help you make that call.
Between 200amp and 400amp there are not a lot of good options. Mainly due to the products available (meter sockets and panels). The one good in between option that won’t break the bank is a 225amp service. We are doing this size service on homes that are right at the limit of a 200amp, but don’t want to pony up for the 400amp service.
The big question is, what SIZE service does my house need??
As electricians we figure this out by doing an electrical load calculation. I don’t want to bore you with the mathematics of it, but I will say it takes into account the square footage of the house plus all the electrical appliances. Our electrical code assumes that not every appliance in the home will be used at the same time, so we get to use a demand factor which reduces the total load calculated by a percentage. Imagine every burner being used on your electric range, with your electric oven on, while running your dryer, washing machine, disposal, dishwasher, microwave, with all your lights on and something plugged into all your outlets ALL AT THE SAME TIME. This is very unlikely, hence the use of the demand factor.
Now a few things don’t use demand factors, such as air conditioning units and electric vehicle chargers. These are taken at their full value. Imagine a house that has 2 central air units at 25 amps each plus a Tesla charger at 48 amps. You are already up to 25 + 25 + 48 = 98amps!! That doesn’t leave a lot of room for the rest of the home.
So which size service should you go with? I’ll give you a few examples below of homes / electrical loads and where they end up. You could compare to your own home and get a sense of it.
Example 1: A 2500 square foot home with an electric dryer, washing machine, dishwasher, disposal, 2 refrigerators, microwave, single A/C condenser, electric range with GAS for heat and hot water comes out to ~107 amps. This house could add an electric vehicle charger, and switch the gas water heater to electric and still be within a 200amp service.
Example 2: 3500 square feet this time, with the same appliances as above with the exception of 2 A/C systems instead of 1. This home comes out to 138 amps. So again, an electric vehicle charger could be added and stay within 200amps. Now if the water heater is switched to electric as well as the EV charger, it will be very close. This is a good example where the 225amp service makes sense.
Example 3: A 6000 square foot house with a washing machine, electric dryer, disposal, dishwasher, microwave, 2 refrigerators, wine fridge, pool pump, 4 A/C systems, electric oven, electric range, and electric water heater. So essentially ALL electric except for heat. This one comes out to ~ 215amps. Now let’s keep in mind a house of this size will likely have other electric appliances such as multiple pool pumps, jacuzzi, pool heater, EV charger etc. When you get to homes of this size a 400amp service is the way to go.
As you can see from the above examples a 200amp service is large enough for most homes, a 225amp service can be a great inbetween and a 400amp service is typically reserved for very large homes with lots of electrical appliances / loads.
I hope the above helps you in choosing your next electrical service. If you still are not sure what size service you need, please feel free to email us firstname.lastname@example.org and we’ll calculate it for you! All we need is the square footage of the home and all the electric appliances.