Power Consumption Calculator: Estimate Your Appliance and Device Energy Use
Calculate electrical power consumption in watts and kWh for any appliance or device. Estimate monthly energy costs and identify your biggest energy users.
Most people have no idea which appliances are costing them the most on their electricity bill. That always-on gaming PC or the old refrigerator in the garage might be doing more damage than you think. A quick power consumption audit can point to changes that pay back in months, not years.
The CalcHub Power Consumption Calculator estimates daily and monthly kWh usage and electricity cost for any device or full household inventory.
The Basic Formula
kWh = Watts × Hours per Day ÷ 1,000 Monthly kWh = kWh per Day × 30 Monthly Cost = Monthly kWh × Electricity Rate ($/kWh)For a 200W gaming PC running 4 hours/day at $0.13/kWh:
- Daily: 200 × 4 ÷ 1,000 = 0.8 kWh
- Monthly: 0.8 × 30 = 24 kWh
- Cost: 24 × $0.13 = $3.12/month
Not terrible. But running it 10 hours/day: $7.80/month. Add a 27" monitor, and you're at $12–$15/month just for a gaming setup.
Common Appliance Wattage Reference
| Appliance | Typical Wattage | Monthly kWh (avg. use) |
|---|---|---|
| Central AC (3-ton) | 3,500W | 350–500 kWh |
| Electric water heater | 4,000–5,000W | 300–450 kWh |
| Clothes dryer | 5,000–7,000W | 40–80 kWh |
| Refrigerator (new) | 100–200W | 30–50 kWh |
| Refrigerator (older) | 300–600W | 80–150 kWh |
| Gaming desktop PC | 200–600W | 15–50 kWh |
| Laptop | 20–60W | 3–8 kWh |
| LED TV (55") | 50–100W | 5–15 kWh |
| LED bulb (replaces 60W) | 8–10W | 1–2 kWh |
| Incandescent 60W | 60W | 7–10 kWh |
| Space heater | 750–1,500W | 50–150 kWh (seasonal) |
| EV charging (Level 1) | 1,400W | 40–80 kWh |
| EV charging (Level 2) | 7,200W | 60–120 kWh |
| Standby/phantom loads | 0.5–50W each | 5–50 kWh combined |
Electricity Rates by US Region
| Region | Average Rate (cents/kWh) |
|---|---|
| Hawaii | 30–45¢ |
| Northeast US (CT, MA, NY) | 18–28¢ |
| California | 20–32¢ |
| Pacific Northwest | 10–13¢ |
| Southeast US | 10–14¢ |
| Midwest | 10–14¢ |
| Texas | 11–16¢ |
The Hidden Culprits: Phantom Loads
Devices in standby mode ("vampire loads") add up:
| Device | Standby Wattage | Annual Cost at 15¢/kWh |
|---|---|---|
| Cable/satellite box | 10–17W | $13–$22 |
| Gaming console (standby) | 1–10W | $1–$13 |
| Microwave (clock only) | 2–4W | $3–$5 |
| Desktop computer (sleep) | 2–5W | $3–$7 |
| Smart speaker | 2–6W | $3–$8 |
| TV (standby) | 0.5–3W | $1–$4 |
| Phone charger (unplugged) | 0.1–0.5W | Negligible |
How do I measure actual wattage of a device?
Use a plug-in energy monitor (Kill-A-Watt or similar) — they're around $25 and measure real power draw including power factor, which can differ from nameplate wattage for motors and transformers. This is more accurate than using spec sheet numbers.
What's the difference between watts and kWh?
Watts measure power (rate of energy use). kWh measures energy (total power used over time). Running a 1,000W microwave for 1 hour uses 1 kWh. That's what the utility bills you for — the total energy consumed, not just the instantaneous power draw.
How much does it cost to run an old refrigerator in the garage?
An older refrigerator (pre-2000) can use 1,500–2,000 kWh per year — at $0.14/kWh that's $210–$280/year. A new Energy Star refrigerator uses 300–500 kWh/year. The garage fridge that "costs nothing because it's already paid off" might actually be your most expensive appliance.
Related Tools
- Electrical Load Calculator — total load for panel sizing
- Battery Life Calculator — how long a battery lasts at given power draw
- Carbon Footprint Calculator — your energy use's environmental impact