Home
Electricity Cost Calculator
Wondering what that space heater or always-on gaming PC actually costs you per month? Old refrigerator vs new fridge — is the upgrade worth the difference? Always-on smart home gadgets adding up to more than you think? This calculator runs the simple math: watts × hours per day × days × rate ÷ 1000 = dollars. Enter wattage from the device's label (or look it up online), typical hours of daily use, and your electric rate. Output: per-day, per-month, and per-year cost plus annual kWh consumption. Use it to decide if that wattage-hungry old appliance is worth replacing.
Enter wattage and hours.
Common appliance wattages
| Appliance | Typical watts |
|---|---|
| LED bulb | 10 |
| Laptop | 50 |
| TV (LED 50") | 100 |
| Refrigerator | 150 (avg, runs ~⅓ time) |
| Window AC | 900 |
| Microwave | 1000 |
| Space heater | 1500 |
| Hair dryer | 1800 |
| Electric clothes dryer | 3000 |
The simple formula
Cost per day = (watts × hours per day / 1000) × rate per kWh
Annual cost = daily cost × 365. Annual kWh = (watts × hours × 365) / 1000.
Worked example: 1500W space heater run 8 hours a day in winter (3 months = 90 days) at $0.16/kWh. Daily = (1500 × 8 / 1000) × 0.16 = $1.92. 90 days = $173. The supplemental heating bill quietly adds up.
High-cost everyday appliances
Annual cost at $0.16/kWh, average residential use:
- Central AC (3-ton): 3,000-4,500 kWh/year → $480-720/year
- Electric water heater (50-gal): 3,500-5,000 kWh → $560-800
- Electric clothes dryer: 800-1,000 kWh → $130-160
- Refrigerator (modern): 400-500 kWh → $65-80
- Refrigerator (1990s pre-EnergyStar): 1,200-1,500 kWh → $190-240 — worth replacing
- Gaming PC (8 hr/day): 800-1,500 kWh → $130-240
- Pool pump (variable speed, 8 hr/day): 1,500-2,500 kWh → $240-400
- Hot tub: 2,000-4,000 kWh → $320-640
- EV charging (12,000 mi/yr, 4 mi/kWh): 3,000 kWh → $480 — vs $1,500/year in gas at 28 MPG
Common appliance wattages
| Appliance | Typical watts |
|---|---|
| LED bulb (60W equivalent) | 9 |
| Laptop (in use) | 50 |
| Modem + router + ONT | 25 (always on = 219 kWh/yr) |
| TV (LED 55") | 100 |
| Refrigerator | 150 avg (cycles, runs ~1/3 of time) |
| Window AC (10K BTU) | 900-1,200 |
| Microwave | 1,000-1,500 |
| Space heater | 1,500 (max wall outlet limit) |
| Hair dryer | 1,800 |
| Coffee maker (brewing) | 800-1,200 |
| Electric range burner (large) | 2,500-3,000 |
| Electric clothes dryer | 3,000-5,000 |
| Electric water heater | 4,500 |
| EV Level 2 charger (40A) | 9,600 |
How to use this calculator
- Power in watts: from the device's nameplate or spec sheet.
- Hours per day: typical daily use.
- Rate ($/kWh): from your electric bill. US national average ~$0.16/kWh; varies from $0.10 (TN, LA, MS) to $0.35+ (CA, NY, MA).
- Output: cost per day, month, year + annual kWh.
- For cycling appliances (refrigerator, AC, freezer): use AVERAGE watts (about 1/3 of nameplate), not nameplate. Refrigerator nameplate 150W but averages 50W over a 24-hr cycle.
FAQ
Where do I find my electric rate? +
Your monthly bill lists $/kWh under "supply" or "generation" charges. Add "delivery" or "distribution" charges to get the total. Or just divide total bill by total kWh used for the all-in rate. The all-in rate is what matters for cost calculations.
Why do refrigerators say 150W but cost less than that implies? +
Because they cycle. The 150W is the compressor's running wattage, but it only runs ~30-40% of the time. Average power consumption is closer to 50W. Modern EnergyStar fridges run ~400-500 kWh/year; 1990s fridges ran 1,200+ kWh/year. Big upgrade opportunity if your fridge is 15+ years old.
What's the worst always-on device in my house? +
Usually one of: pool pump (single-speed running 24/7), 2nd refrigerator/freezer in garage, hot tub heating element, electric water heater (always reheating). Vampire loads from chargers and entertainment equipment add up to 5-10% of total bill but are small per device.
How much do "vampire loads" cost? +
Always-on devices in standby (TV, console, modem, smart speakers, etc.): typical household has 50-100W of constant draw. At 100W × 24 hr × 365 ÷ 1000 = 876 kWh/year = $140 at $0.16/kWh. Plug strips with on/off switches can kill some of this.
What's the cheapest electric appliance to run? +
LEDs (9W per bulb): even running 4 hours/day = 13 kWh/year = $2/year per bulb. Compared to incandescent (60W): 88 kWh/year = $14/year. The savings of LED over incandescent at 5 hours/day is dramatic over a 20-bulb house.
Time-of-use rates — are they worth opting into? +
If you have flexible usage (EV charging at night, dishwasher on delay, pool pump scheduled): typically yes — nighttime rates are 1/3 to 1/2 of daytime rates. If most of your usage is during 4-9 PM peak hours: probably stick with flat rate. Calculate based on your actual usage pattern.
How much does electricity cost vary by state? +
2024 averages: Louisiana $0.10/kWh, Tennessee $0.12, Texas $0.13, Ohio $0.14, US average $0.16, New York $0.23, California $0.30, Massachusetts $0.32, Hawaii $0.42. Picking states is a non-starter, but understanding your local rate is essential for energy decisions.
Do solar panels offset all my usage? +
Depends on size + production + net metering. A typical 10 kW system in moderate-sun region produces 12,000 kWh/year — enough to offset a typical house's full usage. With 1:1 net metering, surplus daytime production credits offset evening grid usage. Solar payback is heavily dependent on local rates and net metering rules — highest in expensive-rate states (CA, MA, NY).