Before you design
The panel question, answered before rough-in
A 1970s Mandarin ranch with a 150 amp service is fine until you add an induction range, a second oven, a larger heat pump and a car charger. This is the calculation that tells you which side of the line you are on.
Before you design
Will the panel carry the house you want?
This runs the optional demand calculation the code uses for an existing dwelling: everything is added up, the first 8,000 volt-amperes counts in full, the rest counts at 40 percent, and the mechanical load is added afterwards at its full value.
Calculated demand
0.0 A
- Connected load
- 0 VA
- After demand factors
- 0 VA
Orientation only. A permit set needs a calculation by a licensed electrical contractor or engineer on your actual plan, and local amendments apply.
Book the panel survey- 01
General lighting and receptacles
3 volt-amperes for every square foot of conditioned floor area. That is the code's blanket allowance for lighting and general-use receptacles; you do not count them individually.
- 02
Small appliance and laundry circuits
1,500 volt-amperes for each 20 amp small appliance branch circuit serving the kitchen and dining areas, with a minimum of two, plus 1,500 volt-amperes for the laundry circuit.
- 03
Appliance nameplates
Add the nameplate rating of every fastened-in-place appliance: range, oven, dryer, water heater, dishwasher, disposal, microwave, pool equipment, well pump.
- 04
Apply the demand factors
Under the optional method for an existing dwelling, the first 8,000 volt-amperes of that total counts at 100 percent and everything above it counts at 40 percent. Nobody runs every appliance at once, and the code recognises that.
- 05
Add the mechanical load at full value
The larger of the air conditioning load or the heating load is added at 100 percent, with no demand factor applied to it.
- 06
Convert to amperes
Divide the calculated volt-amperes by 240 volts. Compare the result with the rating of the existing service. If you are over, or inside about 10 percent of it, plan the service upgrade into the renovation rather than discovering it at rough-in.
What else matters
Five things the number alone does not tell you
What a service upgrade actually involves
A new meter can, a new panel, a grounding electrode system brought up to current requirements, a utility coordination visit and a disconnect period. On a Jacksonville house with an overhead drop, plan on one full day without power and a separate utility appointment.
Why panels fill before they overload
Two different limits are in play. One is the service ampacity. The other is physical space and the number of circuits the panel is listed for. Arc-fault and ground-fault requirements on renovated circuits often mean larger breakers physically, and a 1980s panel can run out of room long before it runs out of capacity.
Aluminium branch wiring
Houses wired between roughly 1965 and 1973 sometimes have aluminium branch circuits. They are not automatically unsafe, but every termination needs approved connectors. We check for it at the first visit because it changes the rewire scope.
Cloth-wire and knob-and-tube
Common in Riverside and Springfield houses. Insurance carriers increasingly decline it, and it cannot be extended. On a whole-home scope we assume a full rewire in those neighbourhoods until we see otherwise.
Load management as an alternative
Where a service upgrade is difficult, listed load-management devices can let an EV charger or a second oven share capacity with an existing load. It is a real option and sometimes cheaper than a new service, but it has to be engineered rather than assumed.
If you are over
What a service upgrade looks like on a real job
- 01
Confirm with a licensed electrical contractor
The calculation on this page is orientation. A permit set needs one prepared against your actual plan, with local amendments applied.
- 02
Coordinate with the utility
An overhead drop or an underground lateral has to be scheduled, and on a Riverside house with an addition the drop often has to move to clear a new roof line.
- 03
Meter can, panel and grounding
New meter enclosure, new panel, and the grounding electrode system brought up to current requirements, which on an older house usually means new ground rods and a bonded water line.
- 04
One day without power
Plan for it, and plan for the refrigerator. We give 48 hours written notice and we do it on a day nobody needs to work from home.
- 05
Inspection, then re-energise
The utility will not reconnect until the inspection passes, so this is one of the few items on a renovation that genuinely cannot be resequenced.
Sequence shown is typical for Duval County. Requirements vary by utility, by jurisdiction and by whether the service is overhead or underground.
Related checks
The other three we run before design
HVAC sizing for added area
Sensible and latent load, duct static pressure, and whether a separate zone beats extending the system.
Windows, doors and wind load
Design pressure per opening, corner zones, impact requirements and product approval numbers.
Floors and subfloor prep
Slab relative humidity, flatness tolerance and the build-up height that decides every doorway.
We run this on the first visit
Panel photographed, area measured, number produced, all before anyone talks about tile.