What service size actually limits
The service size is how much electricity the house can draw at once. It was set when the home was built, for the demands of that era — and household demand has risen enormously since.
- 60-amp — found in older homes that have never been upgraded. Inadequate for most modern households, and frequently a condition insurers and lenders take a view on. Treat it as a cost to plan for, not a curiosity.
- 100-amp — a common minimum and fine for many homes. It becomes constraining once you add air conditioning, an electric vehicle charger, a hot tub, a suite, or electric heat.
- 200-amp — standard on newer and larger homes, and what you want if you plan to add any of the above.
Signs the service is undersized
Breakers tripping regularly, lights dimming when a large appliance starts, a panel that is visibly full with no spare slots, or a proliferation of tandem breakers doubled into single spaces. An inspector will identify the size; you can often read it from the main breaker.
Upgrading
Upgrading a service is not a small job — it involves the panel, often the mast and meter base, permits and an inspection, and sometimes utility coordination. Cost varies considerably with the house and how the supply arrives, so get an electrician's quote on the actual property rather than relying on a general figure.
If you are buying an older Calgary home and intend to add air conditioning or an EV charger, price the electrical upgrade before you write the offer. It is a predictable cost that buyers routinely discover a year later.
Related era issues: aluminum wiring and what to inspect by decade.
Knob-and-tube wiring
Knob-and-tube is the wiring method used in homes built before roughly 1950: individual conductors run through ceramic knobs and tubes, with no ground. In Calgary it is genuinely uncommon. Most of the housing stock is newer than that, and in the oldest inner-city communities most of it was replaced decades ago. What inspectors usually find is a small surviving run in an attic or a basement ceiling, left behind when the rest of the house was updated.
It matters for the same reason service size does: insurance. Insurers routinely ask whether a home has knob-and-tube, and many will not write a policy while active knob-and-tube remains. Because a lender will not advance funds without proof of insurance, an insurance refusal ends a purchase regardless of how well the house shows.
The remedy is replacement of the remaining runs by a licensed electrician, with a permit, and written confirmation that nothing live is left. If an inspector flags it, get both the electrician's quote and the insurer's answer inside your condition period — not afterwards.
Related era items: aluminum branch wiring, what to inspect by build decade, and the red flags that genuinely matter.