Is a 100 amp service on a 640 square foot house with electric baseboard heating adaquate?

Sounds Like enough. Can you list all Appliances, Gas Dryer? Kiln, Welder, Dock, Jacuzzi, InstaHeat(Demand Water Heater)

There is an electric dryer stove and hot water tank

Sounds Like enough. Can you list all Appliances, Gas Dryer? Kiln, Welder, Dock, Jacuzzi, InstaHeat(Demand Water Heater)

There is an electric stove dryer and hot water tank

How much heat? New construction would dictate around 4,000 -5,000 watts.

Your calculating out to about 65.5 amps without the heat if stan I right that pushes you up to 86.3 amp if I where you I would go with a 150A give you some room to expand and your not talking that much of an increase in price.

Doing as much of a standard calculation as info gives:

General Lighting Load: 640 sq. ft x 3VA/sq.ft=1920 VA
2 kitchen Circuits= 3000 VA
laundry Circuit=1500 VA

Total: 6420 VA

1st 3KVA @ 100%----------3000VA
Remainder at 35%---------1197 VA==========3197 VA
Dryer----------------------------------------------------5000 VA
Range----------------------------------------------------8000 VA?
Water Heater--------------------------------------------5000 VA?
Baseboard Heat-----------------------------------------4000 VA?

Total VA-------------------------------------------------25197 VA

25197VA/240 Volts=105 amps

Standard Calculation put you over. If you are allowed to compute the Optional Method, (Check with your local inspector) Using the same information:

General Lighting load: 1920 VA
Kitchen and Laundry: 4500 VA
Dryer------------------5000VA
Range-----------------8000VA?
Water Heater------- 5000 VA?
Baseboard Heat------4000 VA?

Total VA---------------28420 VA

First 10,000 VA @ 100%----------10,000 VA
Remainder at 40%----------------7296 VA

Total VA... 17296 VA
17296 VA/240 Volts===========72 amps


Still cutting it close! Not much room for expansion there. Have you considered gas heat, hot water and range?

Need to correct a few errors in this calculation, and added some clarity, my corrections in red:


Doing as much of a standard calculation as info gives:

General Lighting Load: 640 sq. ft x 3VA/sq.ft= 1920 VA
2 kitchen Circuits= 3000 VA
1 Laundry Circuit= 1500 VA
Total: 6420 VA

1st 3KVA @ 100%----3000 VA
Remainder at 35%----1197 VA
Subtotal................. 4197 VA
Dryer----------------5000 VA
Range---------------8000 VA Allowed Load for one range in dwelling
Water Heater--------4500 VA Typical Load for typical WH
Baseboard Heat------4000 VA? As good a guess as anyone, thou should be higher

Total VA------------25697 VA

25697VA/240 Volts = 107 amps

Standard Calculation put you over.

If you are allowed to compute the Optional Method, (Check with your local inspector)

Per code, the designer is allowed to use the optional methods, rarely does an inspector have any say in this, as the designer is the responsible party in sizing the service.


Using the same information:

General Lighting load: 1920 VA
Kitchen and Laundry: 4500 VA
Dryer------------------5000 VA
Range-----------------8000 VA
Water Heater----------4500 VA
Baseboard Heat------ 4000 VA?

Total VA--------------27920 VA

First 10,000 VA @ 100%--10,000 VA
Remainder,17920 at 40%---7168 VA

Total VA.........................17168 VA
17168 VA/240 Volts======72 amps


Still cutting it close! Not much room for expansion there. Have you considered gas heat, hot water and range?

Sorry OH, but there was a math/typo error in the beginning of the calcs, but with me changing the size WH load, still brought the results close.

A 100 amp service, based on the little information given, and assumptions on the heat KW, is sized adequately.

This is why I dislike doing these calcs, as the info needed is critical.

Sorry for the typo and math error. I thought I double checked it.. but remember I added 3000 and 1197 in my head, instead of using a calculator!

Yeah, I don't know anyone who has ever used the standard calculation. I just assumed there might have been a local requirement in some jurisdictions to use it.

Personally, I put everything I can on natural gas.