Most Hawaii homes built before the late 1990s came with a 100 amp service. That was generous at the time. It is now the single most common bottleneck we find.
Here is how to work out whether yours is still enough, and what actually changes if you upgrade.
What 100 amps really covers
A 100 amp service can run a typical older household comfortably: lighting, a fridge, a washer and dryer, a water heater, a few window units and general receptacles. It was never sized for simultaneous large loads.
The pressure comes from three modern additions. A Level 2 EV charger wants 40 to 60 amps. A ducted heat pump or several mini splits can want 30 to 50. An induction range wants 40. Add any two of those to a 100 amp service and you are out of room.
Signs your service is already at its limit
Lights dim noticeably when the AC compressor starts. The main breaker has tripped at least once. Your panel has no free slots, or has tandem breakers doubled into slots that were not designed for them. You have been told an appliance cannot be added.
None of those are proof on their own. Together they are a strong hint that a load calculation is worth doing before you spend money on an appliance you cannot power.
How a load calculation works
We add up the fixed loads: general lighting by square footage, small appliance circuits, laundry, then the fixed appliances such as the water heater, range, dryer, AC and any EV charger. Standard demand factors are applied so the result reflects realistic simultaneous use rather than everything at once.
The number that comes out tells you whether you need a service upgrade, a sub panel, or simply a rearranged panel. It is a short exercise and it prevents the most expensive mistake, which is upgrading when you did not need to or under-upgrading and doing it twice.
What a 200 amp upgrade involves
A new meter can, new service entrance conductors, a new 200 amp panel, grounding and bonding brought current, and coordination with the utility for the disconnect and reconnect. Inspection follows. Most residential upgrades run a single working day with power off for part of it.
The panel itself is usually the cheapest part. Cost is driven by whether the feed is overhead or underground, how far the meter is from the panel, whether the panel location moves, and how much of the existing grounding can be reused.
When you do not need an upgrade
If the load calculation comes back with headroom, you may only need a sub panel to gain slots, or a load-managing EV charger that throttles when the house draws hard. Both are far cheaper than a service upgrade and both are legitimate solutions.
Ask for the calculation before you accept a quote for a full upgrade. Any electrician should be happy to show you the numbers.