Answer what you can see below. This ranks the likely causes, gives you one safe next check, and tells you clearly when to stop and call a licensed electrician.
Stop and call a licensed electrician or emergency services now if there's smoke, sparks, a burning smell, heat, shock, or water near the problem. Otherwise it's safe to answer the questions below.
What can you see?
Diagnosis
Example result — change the answers on the left and the ranking updates for your situation.
Most likely cause
16 AWG at 50 ft carrying ~15 A exceeds its ~10 A rating — inadequate (overheating/fire risk)
Ranked by fit to your answers
1
Inadequate — load exceeds the cord's safe current rating
90
SAFE NEXT CHECKUse a heavier cord — about 15 A at 50 ft needs at least 12 AWG. A cord that still powers the tool while overloaded overheats inside its jacket, so this is a fire concern, not just performance.
Where to stop. Choosing or replacing an extension cord is homeowner-safe. Manufacturers and fire authorities advise plugging high-draw heating appliances such as space heaters directly into a wall receptacle rather than any extension cord. Anything involving the building's wiring or circuit rating is a licensed electrician's job. This is general information, not a quote and not a substitute for a licensed electrician.
Round-trip drop = 2 × 50 ft × 15 A × 4.016 Ω/1000ft = 6.02 V (5.0% of 120 V). Targets: ≤3% good, 3–5% marginal, >5% excessive.
What to do next
Try the safe next check above. If it doesn't resolve the problem — or if sorting it out would mean opening a panel, touching wiring, or anything past a simple visual check — stop and call a licensed electrician. Don't replace parts on a guess.
If a part needs replacing, likely
Heavier-gauge extension cord
Not your exact situation? Change any answer above and the ranking updates — or try a related situation below.
Named standards and manufacturer guidance, re-verified on a freshness schedule. When a source cannot be re-verified, the dependent rule is suppressed rather than asserted.
The cord powers my heater fine. Why would it not be safe?
A cord delivers power right up until it fails. If the load is over the cord's rating, the conductor overheats inside the jacket even while it works — which is why heaters belong on a wall outlet, not an extension cord.
Does length really matter that much?
Yes. Voltage drop is proportional to length, so doubling the run doubles the drop. A gauge that's fine at 25 ft can be marginal at 100 ft for the same load, which is why the calculator weighs gauge and length together.
How do I turn watts into amps?
On a standard 120 V circuit, amps equal watts divided by 120. A 1500 W heater draws about 12.5 A; a 1200 W tool about 10 A. Use that figure as the load.
Electrical Fault Check provides general diagnostic information only. It is not professional advice, not a quote, and not a substitute for a licensed electrician. Do not work on live wiring. If you see smoke, sparks, burning smell, heat, shock, water exposure, or repeated tripping, stop using the circuit and contact a licensed electrician or emergency services as appropriate.