What is the difference between W (watts) and kWh (kilowatt-hours)?

Watts measure power — the rate a device draws energy at any instant. Kilowatt-hours measure energy — power used over time. A 1000 W (1 kW) device running for 1 hour uses 1 kWh. Running it 3 hours uses 3 kWh. Your electricity bill charges per kWh, not per watt, so to get cost you need both the wattage AND the hours. This tool does that multiplication for you: kWh = (power in kW) × hours, then cost = kWh × tariff.

How much does standby (vampire) power actually cost?

More than people expect. A typical TV, console, microwave, or router draws 1–10 W in standby. Ten such devices at 5 W each, sitting idle 24 hours a day, burn about 5 × 10 × 24 / 1000 = 1.2 kWh a day, roughly 438 kWh a year — $60–120 depending on your rate, paid for doing nothing. This calculator applies the standby figure only to the idle hours (24 minus the active hours), so it never double-counts the time the device is fully on.

My utility uses tiered (block) pricing — how do I handle that?

Tiered tariffs charge different rates per kWh once your monthly usage crosses a threshold. This tool uses a single flat rate, which is the right model when you want the marginal cost of one more appliance: enter the rate of the tier your household sits in (usually the highest tier you reach), and the per-day / per-month numbers reflect what that device adds at the margin. For a full tiered bill, run each tier's kWh band at its own rate and add them.

Why does monthly × 12 not exactly equal the yearly figure on other sites?

Because many calculators use 30 days for a month, which makes 30 × 12 = 360 days — five days short of a year. This tool uses 30.44 days per month (365.25 ÷ 12, the true average including leap years), so the monthly and yearly numbers stay consistent. The yearly figure is computed from 365.25 days directly, not by multiplying the month.

Is the wattage on my appliance's label the real running power?

The nameplate rating is the maximum draw, not the average. Motors, compressors, and heating elements cycle on and off — a fridge rated 150 W might average 35–45 W over a day because the compressor only runs part of the time. For cycling appliances, either use the annual kWh figure from the energy label (divide by 365 for a daily average) or enter an estimated average wattage rather than the nameplate peak.

Does this work for solar, EV charging, or three-phase loads?

The math is the same: any load expressed as power × time gives kWh. For an EV, enter the charger output (e.g. 7.4 kW) and the hours you charge. For solar self-consumption savings, enter the load you offset and use your tariff as the value of each avoided kWh. Three-phase industrial loads work too — just enter the total real power in kW.

Find out what running the air conditioner all summer costs

A window AC pulls about 1200 W and you run it 10 hours a day in July and August. Enter 1200 W, 10 hours, your tariff (say $0.17/kWh). The tool shows 12 kWh a day, about $2.04 daily and roughly $62 a month. Now you can decide whether a $20/month efficiency upgrade or a smart thermostat that trims two hours a day actually pays back. Two hours less is 2.4 kWh saved daily, about $12 a month — the thermostat clears its cost in two seasons.

Budget the electricity for a crypto mining rig

A mining rig drawing 1300 W runs 24 hours a day. Enter 1300 W, 24 hours, your industrial or residential rate. The yearly kWh (about 11,388 kWh) times your tariff is the hard floor your mining revenue has to beat before you make a cent. At $0.12/kWh that is roughly $1,366 a year per rig — multiply by your rig count. Seeing the annual number in money, not hashrate, is the reality check most rig calculators skip.

Size the electricity bill for an always-on home server

A NAS or home lab server idling at 60 W runs 24/7. That is 1.44 kWh a day, about 526 kWh a year. At $0.20/kWh it is roughly $105 a year just to keep it powered — before any spin-up spikes. Add a second row for the network switch and UPS at 25 W, and the total tells you whether consolidating onto one low-power box is worth the migration effort. Standby fields let you model the difference between sleep and full idle.

Audit a whole household bill appliance by appliance

Your bill says 600 kWh last month and you have no idea where it went. Add a row per major load: fridge (average 40 W, 24 h), water heater (3000 W, 2 h), washer (500 W, 1 h), lights (200 W, 5 h), AC, TV with standby. The running total in kWh should approach your metered figure. When it does, you can see at a glance which appliance owns the biggest slice — usually the water heater or AC — and where trimming hours moves the needle.

Compare two appliances before you buy

A 55-inch OLED TV draws about 100 W; an older plasma drew 300 W. At 5 hours a day and $0.17/kWh, the OLED costs about $31 a year to run, the plasma about $93 — a $62 annual gap that often outweighs a modest price difference over the set's life. Enter each one as a row, read the per-year cost, and let the running cost, not just the sticker price, decide.

Electricity Cost Calculator — kWh and Cost per Day, Month, Year

Power × hours × tariff → kWh and cost per day, month, and year — add multiple appliances, account for standby — browser-only.

Runs locally
Category Calculator
Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.

Enter an appliance’s power and how many hours a day it runs, plus your electricity tariff per kWh. You get the energy it uses and what it costs — per day, month, and year. Add more rows to rebuild a whole bill.

CurrencyTariff (per kWh)Unit

Appliances

Power (W)Hours / dayStandby power (W)

Runs for the idle hours (24 − active). Optional.

Energy + Cost

Per day

$2.04

12 kWh

Per month

$62.09

365.3 kWh

Per year

$745.11

4,383 kWh

What this tool does

A free electricity cost calculator that turns a device's nameplate wattage, the hours it runs each day, and your per-kWh tariff into the numbers you actually want: kilowatt-hours used and money spent, broken down per day, per month, and per year. Enter power in watts or kilowatts — a 1500 W space heater run 8 hours a day uses 12 kWh and, at $0.17/kWh, costs about $2.04 a day, $62 a month, $745 a year. Add as many appliances as you like to rebuild a whole electricity bill line by line: air conditioner, fridge, gaming PC, an always-on home server, a mining rig. Each row supports an optional standby (vampire) draw that runs during the idle hours of the day, so a TV that is "on" 4 hours is also counted for the 20 hours it sits in standby. Pick from common currencies (USD, CNY, EUR, GBP, JPY, AUD, INR) and seed the tariff with real residential averages, or type your exact rate from the bill. The monthly figure uses 30.44 days (365.25 ÷ 12) so monthly × 12 lines up with the yearly total instead of drifting. Inputs sync to the URL so a "share this estimate" link reopens the same calculation, and your currency and unit preference are remembered between visits. 100% client-side — no signup, no upload, instant math.

Tool details

Input: Text + Numbers; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 14 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Calculator · Finance; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How Electricity Cost Calculator fits into your work

Use it for fast estimates, comparisons, and planning numbers before you make the final call.

Calculation jobs

Getting a realistic range before a purchase, plan, workout, or schedule decision.
Comparing scenarios by changing one input at a time.
Turning rough assumptions into a number you can discuss.

Calculation checks

Double-check units, dates, rates, and rounding assumptions.
Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
Save the inputs that produced an important result so you can reproduce it later.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Find out what running the air conditioner all summer costs
A window AC pulls about 1200 W and you run it 10 hours a day in July and August. Enter 1200 W, 10 hours, your tariff (say $0.17/kWh). The tool shows 12 kWh a day, about $2.04 daily and roughly $62 a month. Now you can decide whether a $20/month efficiency upgrade or a smart thermostat that trims two hours a day actually pays back. Two hours less is 2.4 kWh saved daily, about $12 a month — the thermostat clears its cost in two seasons.
Budget the electricity for a crypto mining rig
A mining rig drawing 1300 W runs 24 hours a day. Enter 1300 W, 24 hours, your industrial or residential rate. The yearly kWh (about 11,388 kWh) times your tariff is the hard floor your mining revenue has to beat before you make a cent. At $0.12/kWh that is roughly $1,366 a year per rig — multiply by your rig count. Seeing the annual number in money, not hashrate, is the reality check most rig calculators skip.
Size the electricity bill for an always-on home server
A NAS or home lab server idling at 60 W runs 24/7. That is 1.44 kWh a day, about 526 kWh a year. At $0.20/kWh it is roughly $105 a year just to keep it powered — before any spin-up spikes. Add a second row for the network switch and UPS at 25 W, and the total tells you whether consolidating onto one low-power box is worth the migration effort. Standby fields let you model the difference between sleep and full idle.
Audit a whole household bill appliance by appliance
Your bill says 600 kWh last month and you have no idea where it went. Add a row per major load: fridge (average 40 W, 24 h), water heater (3000 W, 2 h), washer (500 W, 1 h), lights (200 W, 5 h), AC, TV with standby. The running total in kWh should approach your metered figure. When it does, you can see at a glance which appliance owns the biggest slice — usually the water heater or AC — and where trimming hours moves the needle.
Compare two appliances before you buy
A 55-inch OLED TV draws about 100 W; an older plasma drew 300 W. At 5 hours a day and $0.17/kWh, the OLED costs about $31 a year to run, the plasma about $93 — a $62 annual gap that often outweighs a modest price difference over the set's life. Enter each one as a row, read the per-year cost, and let the running cost, not just the sticker price, decide.

Common pitfalls

Mixing up power and energy. People multiply watts by the tariff directly — but the tariff is per kWh, not per watt. You must convert watts to kilowatts (÷1000) and multiply by hours first. This tool does it for you, but if you do it by hand, a 100 W bulb is 0.1 kW, not 100.
Using the nameplate wattage for cycling appliances. A fridge or AC labelled 150 W or 1200 W does not draw that continuously — the compressor cycles on and off. Entering the peak wattage for 24 hours overstates a fridge's cost two to four times. Use the average or the energy-label annual kWh instead.
Forgetting standby hours overlap with active hours. Standby power only applies when the device is NOT actively on. This tool subtracts active hours from 24 automatically, but if you add standby into the active wattage by hand you will double-count the on-time.

Privacy

Every number stays in your browser. The kWh and cost math is plain JavaScript that runs on this page — no appliance list, wattage, or tariff is ever sent to a server, and there is no analytics on what you calculate. The one caveat: the shareable URL encodes your primary appliance's power, hours, standby, and tariff in the query string (e.g. ?p=1500&h=8&r=0.17), so a "share link" pasted into chat or email records those values in the destination's access log. The numbers are not sensitive, but if you would rather not expose them, copy the summary text instead of sharing the URL. Your currency and unit preference are stored only in this browser's localStorage and never leave the device.

FAQ

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Electricity Cost Calculator — kWh and Cost per Day, Month, Year

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Electricity Cost Calculator fits into your work

Calculation jobs

Calculation checks

Good next steps

Real-world use cases

Find out what running the air conditioner all summer costs

Budget the electricity for a crypto mining rig

Size the electricity bill for an always-on home server

Audit a whole household bill appliance by appliance

Compare two appliances before you buy

Common pitfalls

Privacy

FAQ

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