Electrical amp service
fromPok
| Posted in General Questions on
Good Morning. With our new build, I estimated the electrical load with
electrical dryer, electrical double oven, well pump, geo thermal pump and a electric car charger at https://ask-the-electrician.com/residential-electrical-load-calculation.html#beginAdv
The calculator shows, we need to move above 200 AMP service and closer to 300 AMP service.
Is there some thing like 300 AMP? If not, what is the next level upgrade?
Please look at attached PDF.
As always, thank you for insights. FYI.. I am located in New York State serviced by central Hudson.
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Replies
I can't provide any advice, but for curiosity I ran my house details through that calculator and came up with 175A. I can't remember the exact number I had using the Canadian code rules at time of build, but it was definitely less than 100A. Even that was conservative, as I'm not sure we've ever gone over 50A.
15,000w for a geothermal heat pump? Seems extreme for a house that size. That implies a heat load of like…150kbtu/h. Geothermal can also supply domestic hot water using a desuperheater, so you could save those watts too.
Deleted
It looks like you had an oven on your loads, but not a stove top. I'm guessing based on having an electric oven, you have both?
It looks like that calculator is just summing up all the loads in the house and using that. I'm not sure how the code calculates panel size, but it might be different.
You can get 400Amp panels or a pair of 200 amp panels, not sure if 300 is an option.
You are looking at dual 200 amp service. If you do that and intend to run a generator at some point in the future make sure you can live with your choice of loads on each load panel. You will most likely be able to feed the generator only to one side so make your choices wisely.
The next step up from a 200A service is a "400A" service (which is usually actually only 320A). There is no standard for "300A" service.
I question the need for 300A service here. A typical electric dryer needs a 30A circuit, and will use 5kw. A typical double oven is usually a 40A circuit, but maye be a 50A circuit for 10kw. A well pump is unlikely to exceed about 10A, or around 2kw, and it's a very intermittent load that won't ever be running for extended periods of time. Car chargers can very, but a typical level 2 charger will use a 40A circuit for 32A of actual load (a bit shy of 8kw). I have no idea what your heat pump may draw since there are so many variations, but I'd be surprised if it's more than 30A and about 5kw of load.
If we add up those loads, we get 5kw (dryer) + 10kw for a BIG double oven + 8kw for the charger, and another 5kw for the heat pump. That's a total of 28kw, which is about 117A at 240v. Derate all that for the 80% rule (which doesn't usually apply to all these loads, but we're being extra conservative here), and you're at 146A. Even when the well pump is running, you're only up at about 156A, which is just a bit over 75% of the standard 200A residential electric service, and chances are you won't run at that load much, for very long, if ever.
You're probably fine with a 200A service here. A lot of people seem to think they need more than that, but they are almost always way overestimating their actual loads. I even know of one house in my area with a 400A service that is fed from a dedicated 25KVA transformer on the pole -- which is good for about 104A. Some engineer at that power company thought "yeah, suuuure" when that homeowner ordered their "400A" service too.
Bill
On the EV side of things, there are getting to be larger Level 2 chargers I would think. The F150 Lightning "Charge Station Pro" requires a 100amp breaker. And I would plan to have two basic level 2 chargers at home for the future, lots of families have two+ cars and likely in the next 5 or 10 years both will be electric.
With that said, my utility gives the option to put your EV charger on it's own meter at a special rate with a better night time rate. This frees up your panel and you don't need to have your whole home on the same time of day rate if you don't want it.
Those "cheaper power at night" rates are usually called "time of day" rates. I find that they save me money for my entire house, and I have my entire house on such a rate. I save around $30-50 every month that way. Keep in mind that most of the power you use is probably at night anyway if you are at work during the day, and all day on weekends is usually also considered "off peak".
If you have a 100A charger, then I could see possibly needing beefier service. Note that just hanging the charger off the meter doesn't mean you can get by with lighter service, since the SERVICE is also feeding the meter... You have to tell the utility what you need so that they can install the right stuff to safely feed your system.
Bill
Bill - Thank you.. This is very useful.
I would consult with a reputable local electrical contractor