When to upgrade from 200A service

[MerlinsBeard]

I'm in the process of getting quotes for electric work and trying to determine if it's pertinent to think about a upgrade.

I attempted to do a load calc of my house. Currently it is 2 stories with unfinished basement.

1. General Lighting (SQ FT x 3 VA/SQ FT) [Table 220.12]

3 x 2390 sqft = 7170 VA

2. Small appliance circuits (1500 VA per circuit) minimum 2 [220.52(A)]

2 x 1500 VA = 3000 VA

3. Laundry Circuit (1500 VA per circuit) [220.52(B)]

1 x 1500 VA = 1500 VA

4. General lighting Load = 11670

Net General Light Load = 1st 3000 at 100%, remainder at 35%

3000 + (11670 - 3000) * .35
3000 + 8670 * .35
3000 + 3035

Net General Lighting Load [220.42] = 6035

5. Fixed Appliance load

Garbage Disposal = 1127 VA
Microwave = 1800 VA
Dishwasher = 1152 VA
Water Heater = 4500 VA
Basement Freezer I couldn't find any nameplate so ignoring

3 or less Appliances, Total Appliance VA
4 or more Appliances, 75% of Total Appliance VA [220.53]

Total = 8579 * .75 = 6434 VA

6. Kitchen range = 11200 VA
7. HVAC = 5568 VA (heatpump A/C compressor plus fan, natural gas when needed)
8. Dryer = 5400 VA on nameplate (5000 VA minimum)

Total gives me 34637 VA / 240 or 144A.

There are two home improvement items I'm looking at in the next 1-3 years.

This year I'm planning to run electric to a 10x16' shed power with receptacles and lights, and possibly some equipment for a workshop (compressor, woodworking, no welding), and possibly a mini-split.

Future expansion in the house would be converting unfinished basement into living space which would add roughly 1000 sqft to the general lighting section, which would add about 5A. It's very possible that the house A/C would need to be updated with either a larger heatpump or a 2nd heatpump.

I'm not planning on adding electric vehicle charging in the near future.

How do I know when I've reached the threshold of needing a service upgrade?

 

[dcg9381]

How do I know when I've reached the threshold of needing a service upgrade?

It appears to me your load calc is well thought out. Note, IMHO, it's also very much on the upper end - designed to make sure you're provisioned.

The practical method might be to clamp on an amp-meter for a week (or a wifi device tracks actual power draw) and see where you're at in terms of current use.

Your house is 2400 sqft, even adding another 1000 sqft - generally that's well in the spec of 200A service, only getting outside of it if you're running a massive pool (multiple pumps) with big electric heat.

But actually measuring your use over a week/month or so to observe peak would be my next step.


In theory, you could bust 200A, but when is the last time you turned all the burners on your stove on to HIGH at the same time?


I have 90A to a 2400 sqft shop. That powers 2 ductless units, a kitchen (electric), a hot tub, multiple RV connections, not to mention the usual outlets, lighting, PCs, AV. I've had 3 RVs attached at the same time in the summer. It'd be hard for me to use that much power, even with a 2400 sqft shop and being a part time welder...

 

[MerlinsBeard]

That's a great idea dcg, thanks! Anyone have any personal recommendations from devices they've used to track amp draw over time?

I don't mind spending a bit (in the low hundreds range) to get an accurate picture of my electric usage.

 

[wyliesdiesels]

FYI mike holt has a load calc sheet that will make things easier to calculate

 

[ddawg16]

I think you're just a 'little' high on your lighting. By now, all of your lighting should be LED or CFL.

If you need more than 20A for lighting....might want to re-think

I've got about 2100 sq ft...and a detached 2-story garage. 50A to the garage..

I have never tripped a breaker on anything....unless I was messing with the wiring.

 

[MoonRise]

In theory, you could bust 200A, but when is the last time you turned all the burners on your stove on to HIGH at the same time?

Not an electric stove, but I pretty regularly have the burners on my gas stove running at MAX, as well as the gas oven/broiler going at the same time.

Let's see, a big pot of water going for pasta or potatoes or other boiled food on one burner, another burner doing a sauté or sear, another burner doing the sauce, and then the last burner doing another item. Pretty regularly. Oven baking or broiling at the same time.

Not always, but pretty regularly. YMMV and all that.

All electric home obviously uses (or can use) more electrical power than a house that uses gas for heating purposes (domestic hot water, cooking, gas dryer, etc).

Stove, oven, water heater, AC, appliances, that big Miller 330AB/P you got because the price was too good to pass up, the EV you didn't think you wanted or needed but got anyway a few years from now, the second HVAC system for the house, the minisplit for the shop/basement, and you honestly would NEED more than 200A of electrical service.

Double check to what is even 'available' from your electric service provider without hoops to jump through. Last time I looked (years ago), my area was 200A service was pretty much it for 'usual' residential service.

 

[dcg9381]

That's a great idea dcg, thanks! Anyone have any personal recommendations from devices they've used to track amp draw over time?

I don't mind spending a bit (in the low hundreds range) to get an accurate picture of my electric usage.

I haven't used one. The simple solution is an amp meter that clamps on, although you couldn't let it sit there for a week.

I have a transfer switch by Generac that has a clamp on deal with an app that is designed to track power use and determine power loads. I don't have it up yet, so can't tell you how well it works.

There are several similar devices: Google "home energy monitor" - I'd look for one that can clamp the main.

I agree with others - see if alternate service is even available. Here we can get 320A and 400A service. My guess is that in most cases, bringing 300A to the house would mean replacing your main panel.. I suppose you could add a panel upstream of your main (making it a sub-panel) and wire the basement separately, but your case it sounds like loads are on the main panel.

 

[Jim greengo]

Clamp an amp meter on each leg of service before the main on panel.
Turn on all the things you normally use and check the numbers.
Then switch to other leg of service and repeat process.
You might be surprised at how little power you're actually using.

 

[TractorJeff]

There was/is on AMAZON a less than $100 Home Monitor that has Split CT's to enable ease of installation. Pre-Covid, We were talking about it at Work. Possibly installing to monitor Leg balance. Get the one with Dual CT's or else monitor for 2 weeks moving one CT to other Leg for 2nd week.

 

[Innovate1]

They make small (relatively) clamp on current transformers that are made to go into a power panel. Some are made to go to other electronics to monitor and some are just the CT that is meant to feed an ammeter. We have some smaller ones at work that are 1000:1 meaning for 10 amps in you read 10 mA (0.01A) on the meter. Those should allow you to place them and put the cover back on the panel so it isn't open for a week.

A lot of 320A meter bases have dual lugs. Around here it is common to use them with two 200A panels. Talk to your power company. If they have that you could just add another panel and leave the existing.

For measuring load think about what season your heating/cooling load is highest. It depends on your power source for each. I have gas heat so summer cooling is higher load.