Electricity Cost Calculator

How to calculate electricity cost

Every electricity cost calculation is the same four steps. Utilities bill in kilowatt-hours (kWh), so convert everything to kWh first.

1. Find the watts. Look at the label or nameplate. If it lists amps and volts instead, multiply them: watts = amps × volts.
2. Convert to kilowatts. Divide watts by 1,000. A 1,500 W heater is 1.5 kW.
3. Multiply by hours of use. kW × hours = kWh. The heater for 5 hours is 7.5 kWh.
4. Multiply by your rate. kWh × price per kWh = cost. 7.5 kWh × $0.17 = $1.28.

Worked examples at 17¢/kWh

Compressor devices (fridges, AC, freezers, heat pumps) cycle on and off. Use the duty cycle field in the calculator, or the preset, instead of assuming full power all day.

What do common kWh amounts cost? (at 17¢/kWh)

Energy cost only. Your bill also includes fixed charges and taxes. The Monthly bill tab adds them.

kW, kWh, watts and amps: how they fit together

Watts (W) and kilowatts (kW) measure power, how fast a device uses energy at one moment. 1 kW = 1,000 W. Kilowatt-hours (kWh) measure energy, the amount used over time. Think of kW as speed and kWh as distance travelled. You pay for the distance.

Use the kW · kWh · Amps tab to run any of these. It also shows what 1 watt costs running all year: at 17¢/kWh, 1 W running 24/7 for a month is 0.72 kWh.

Rule of thumb for always-on devices: every 1 W of constant draw uses about 8.76 kWh a year.

How to calculate your electricity bill from the meter reading

1. Read the meter. Digital meters show kWh directly. On dial meters, read the dials left to right and take the lower number when a pointer sits between two digits.
2. Subtract. Current reading − previous reading = kWh used. If your bill lists both readings, use those.
3. Multiply by the rate. If your plan has tiers, charge the first block at the tier-1 price and the rest at the tier-2 price.
4. Add fixed charges. Many utilities add a monthly customer or service charge no matter how much you use.
5. Add taxes and fees. These are usually a percentage of the subtotal.

The Meter reading tab does all of this and projects a 30-day bill from your actual days of use.

How much does it cost to run common appliances?

Typical running watts and the cost at your rate (17¢/kWh). Use is a typical day. Real wattage varies by model, age and settings, so check your label or measure with a plug-in watt meter.

Quick answers

• How many watts does a fridge use? About 100–250 W while the compressor runs, roughly 1–1.5 kWh a day averaged over 24 hours.
• How many watts does a laptop use? Typically 30–90 W, more when charging and under heavy load.
• How many watts does a computer monitor use? Usually 15–50 W, depending on size and brightness.
• How much does a gaming PC cost in electricity? At 300 W for 4 hours a day, about 36 kWh a month. That is roughly $6 at 17¢/kWh.
• Do dryers use a lot of electricity? Electric dryers are among the biggest single appliances: 2,000–5,000 W. One 1-hour load is about 3 kWh.
• How many watts does it take to run a house? It varies widely. Average use is around 1.2 kW over a day, but the peak when many large loads run together can be several kW. Panels are commonly rated 100–200 A.

Electricity rates by state

Average residential price per kWh by state. Click a column to sort, or click Use this rate to load it into the calculator. Your own plan will differ: these are state averages.

Source: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.B, residential average price, August 2025 data. Prices change monthly.

How to calculate the cost of charging an electric car

Example: a 75 kWh battery charged from 20% to 80% adds 45 kWh. At 90% charging efficiency the wall supplies 50 kWh. At 17¢/kWh that is about $8.50.

• Cost per mile at home = rate ÷ (miles per kWh × charging efficiency). At 3.5 mi/kWh, 90% and 17¢ that is about 5.4¢ per mile.
• Is EV charging cheaper than gas? At home, usually yes. Gas at $3.30 and 30 mpg costs 11¢ per mile. Public DC fast charging can cost several times the home rate and narrow or erase the gap, so compare with your local prices.
• Charging time = kWh from the wall ÷ charger kW. A 7.2 kW Level 2 charger adds about 7 kWh an hour. Fast chargers slow down as the battery fills.
• Are electric car charging stations free? Some are, such as certain workplaces, hotels and retailers, but most public stations charge by kWh or by the minute.

Run your own numbers in the EV charging tab.

Heating and cooling costs

Heating and cooling are usually the biggest items on an electric bill. The formula is the same, but the running hours are the hard part.

• Air conditioner watts: watts ≈ BTU per hour ÷ EER. A 10,000 BTU window unit at EER 10 draws about 1,000 W, or 1 kWh for each hour the compressor runs.
• Space heater: almost every watt becomes heat. 1,500 W costs 1.5 kWh × your rate for every hour on, about 26¢ an hour at 17¢/kWh.
• Heat pumps and mini-splits: they move heat instead of making it, so they can deliver 2–3 times the heat per kWh of a resistance heater. This is why they often cost much less to run.
• Electric water heating: a tank element draws 4,000–5,500 W and runs a few hours a day in total. It is often one of the largest loads in an electric home.
• Hot tubs: highly dependent on climate, cover and temperature setting. Use the hot tub preset and lower the duty cycle for mild weather.

Try these in the Appliance cost tab by picking Central AC, Heat pump, Space heater or Hot tub.

How much solar do I need?

Example: 900 kWh a month, 4.5 peak sun hours and 80% system efficiency: 900 ÷ (30 × 4.5 × 0.8) = 8.3 kW. With 400 W panels that is about 21 panels.

Peak sun hours are the full-sun-equivalent hours per day at your location. Shade, roof angle and direction, local net-metering rules and incentives all change the real answer, so treat this as a starting estimate for conversations with installers. The Solar sizing tab adds cost and simple payback.

Is electricity cheaper at night? Peak and off-peak rates

Only on a plan that prices it that way. On a flat-rate plan, every hour costs the same. On a time-of-use plan, peak hours (often late afternoon to evening) cost more and off-peak hours (overnight, sometimes midday) cost less.

The best loads to shift are the ones you can schedule: EV charging, dishwashers, dryers, pool pumps and water heating. Enter your plan's two prices in the Peak vs off-peak tab to see the saving. Check your utility's schedule: peak hours, seasons and weekends differ.

Business electricity rates and cost

Commercial bills usually have more parts than a home bill: an energy charge per kWh, a demand charge based on your highest kW draw in the billing period, and a fixed customer charge. Business plans often have a lower per-kWh price than residential, but a short spike in demand can raise the whole bill.

Enter your readings, tiers and demand charge in the Meter reading tab. Your tariff sheet from the utility lists the exact numbers.

How to lower your electric bill

• Start with the biggest rows. The Monthly bill tab ranks your appliances by cost. Cooling, heating and water heating usually lead.
• Set the thermostat a few degrees closer to outdoor temperature when you are away or asleep.
• Swap bulbs for LEDs. A 10 W LED replaces a 60 W incandescent for the same light.
• Hunt standby loads. Always-on boxes at 5–15 W each add up: 10 W all year is 87.6 kWh.
• Shift flexible loads off-peak if your plan has time-of-use pricing.
• Clean AC filters and seal leaks. Less runtime means fewer kWh.
• Check your plan. A cheaper rate for the same kWh beats any habit change. Compare plans if you can choose a retailer.

About these numbers

Results are estimates. Appliance wattages are typical values and real products vary, so measure or read the label for precision. State prices are average residential rates from the U.S. Energy Information Administration (Electric Power Monthly, Table 5.6.B, August 2025 data), and your own plan may be higher or lower. Gas and public-charging prices in the EV tool and the installed solar cost are editable assumptions, not quotes. Solar and EV results do not include incentives. Calculations run entirely in your browser and nothing you enter is sent to a server.