Short answer
Start by confirming whether the spike is real usage or a billing/seasonal change, then systematically isolate the load. Read your meter (or smart meter app) to see current kW draw, turn off large suspects (water heater, HVAC, EV charger, pool/spa), and use a breaker-by-breaker test to find the circuit causing the jump. Measure individual appliances with a plug-in energy monitor or clamp meter. If you find persistent high draw you can’t trace, or you notice warm breakers, burning smells, or flickering, call a licensed electrician.
Why usage suddenly jumps
A big increase usually comes from:
- A new or forgotten high-watt device (space heater, dehumidifier, EV charging, heated floors, heat tape, pool/spa pump/heater)
- HVAC running dramatically more (weather swing, aux/heat strips stuck on, clogged filter)
- Water-related issues that make heaters/pumps run constantly (leaky hot water line, water heater element stuck on, well/sump pump short cycling)
- A malfunctioning appliance (freezer with bad gasket or dirty coils, pool pump schedule change)
- Time-of-use rate changes can affect cost; verify your actual kWh went up, not just the bill.
Tools and materials
- Plug-in energy monitor (e.g., Kill A Watt) for 120V plug loads
- Clamp meter with inrush/amp measurement (for circuits; $40–$100)
- Non-contact voltage tester and insulated screwdriver (for basic safety)
- Smart plug(s) with energy monitoring (for ongoing tracking; $10–$30)
- Infrared thermometer or thermal camera (optional) to spot hot breakers/motors
- Notepad or spreadsheet app; flashlight; labels for your panel
- Whole-home energy monitor (optional, e.g., Emporia/Sense; $150–$300)
Step-by-step troubleshooting
- Verify the spike
- Compare the latest bill’s kWh to the same period last year and the prior month. Check number of days in the billing cycle and rate changes.
Read your meter today and again tomorrow at the same time to confirm daily kWh. Many smart meters display instantaneous kW or have an LED that blinks (e.g., 1000 blinks per kWh). A fast blink rate means high draw.
Check the obvious big loads
Temporarily switch off or unplug likely culprits:
- Electric water heater (240V, often 3500–4500W)
- HVAC heat pump/furnace electric heat strips
- EV charger (Level 2 is typically 7 kW+)
- Pool/spa pump and heater
- Space heaters, dehumidifiers, portable ACs
- Well or sump pump
Watch the meter or utility app after each change to see if kW drops. If it does, you found the category of load.
Do a breaker isolation test (safe method)
Turn off or unplug sensitive electronics first.
At the panel, turn off all branch breakers (leave main ON). Note the meter/kW reading. This is your baseline (should be near zero).
Turn on breakers one at a time, waiting 30–60 seconds and observing the meter each time. A big jump points to the problem circuit.
Once a circuit is identified, inspect the connected rooms/appliances and unplug devices to narrow it down.
Measure specific devices
Use a plug-in energy monitor for 120V devices: refrigerator, dehumidifier, space heater, aquarium, computers/servers. Let it run 24–48 hours for a good average.
For 240V or hardwired loads (water heater, HVAC air handler, well pump), use a clamp meter on the circuit conductors or install a whole-home monitor. If you’re not fully comfortable opening a panel, call a pro.
Investigate common hidden culprits
HVAC: Check for aux heat running (often shows as “Aux” or “Heat” on the thermostat). Replace filters. A heat pump stuck on strips can add 30–60 kWh/day.
Water heater: Set to 120°F. Check for hot pipe staying hot when no water is used (possible leak or recirculation pump running nonstop). Inspect T&P valve discharge pipe for warm drip.
Well/sump pumps: Short cycling from a failed well pressure tank bladder or a stuck sump float can run a pump constantly. Listen for frequent starts.
Refrigeration: Clean condenser coils; check door gaskets. A garage fridge in hot weather can double usage.
Outdoor/aux: Roof heat tape, RV plugged into house, pond heaters, landscape transformers, attic fans left on.
Typical load impacts
Device Approx. draw Potential kWh/day
Space heater 1.5 kW 12–36 (8–24 hrs)
EV Level 2 7.2 kW 14 (2 hrs) to 36 (5 hrs)
Electric water heater 3.5–4.5 kW 8–20 if running a lot
Dehumidifier 300–700 W 3–12
Pool pump 800–2000 W 10–24 (12 hrs)
Heat strips (aux heat) 5–15 kW 20–60+
Well/sump pump (fault) 500–1500 W 5–30
Safety considerations
- Panels contain live parts even with the main off. If you need to remove the dead front cover or clamp inside the panel, consider hiring an electrician.
- Use only one hand in the panel, wear dry gloves, stand on a dry surface, and never touch bus bars.
- Label circuits as you go to avoid confusion later.
Tips for best results
- Log readings: time, breaker changes, and meter kW. Patterns help find intermittent loads.
- Schedule big loads: pool pumps and EV charging in off-peak hours (if on TOU rates).
- Install a whole-home energy monitor for ongoing visibility and alerts.
- Clean HVAC filters and fridge coils quarterly to prevent runtime creep.
Common mistakes
- Assuming the utility is wrong before checking your own meter and loads (meter errors are rare).
- Overlooking detached garages, basements, or outdoor circuits that run unseen.
- Forgetting a “temporary” space heater or dehumidifier left on after a cold snap or flood.
- Misreading cost spikes as usage spikes (rate/taxes/fees or longer billing periods).
When to call a pro
- You find a large unexplained “always-on” draw and can’t isolate it.
- Breakers feel hot, you smell burning, see discoloration, or hear buzzing.
- Repeated GFCI/AFCI trips, flickering lights, or voltage swings (possible neutral/service issue).
- You’re uncomfortable opening the panel or measuring 240V circuits.
- You suspect a faulty utility meter; an electrician can document findings to support a utility test (may be a fee if the meter tests fine).
Rough costs and time
- Initial DIY audit: 1–3 hours
- Plug-in monitor: $20–$35 each; smart plugs $10–$30
- Clamp meter: $40–$100
- Whole-home monitor: $150–$300 (plus 1–2 hours install)
- Electrician diagnostic: typically $150–$300 for a service call
With a methodical approach—validate, isolate by circuit, then measure devices—you’ll usually find the culprit within a day or two and prevent repeat surprises.