nrtechstudio.com100% client-side -- your numbers never leave this browser
Energy Cost Calculator
Turn watts, hours, and your electricity tariff into real money: daily, monthly, and yearly cost. Flat rates, tiered slabs, time-of-use pricing, budget reversal, efficiency comparisons, and side-by-side tariff comparison.
kWh -> cost in one stepTiered & time-of-use tariffsBudget -> hours reverseCompare tariffs by country
⚡ Calculate your energy cost
Pick a mode below. Everything updates live as you type. Set your currency symbol once — it applies everywhere.
Copy it from your electricity bill.
Cost per day
$0.00 / day
0
kWh / day
$0
per month (x30)
$0
per year (x365)
0
kWh / year
Formula: kWh = watts ÷ 1000 × hours; cost = kWh × tariff. Month = day × 30, year = day × 365.
Model block tariff / increasing-tier rates: the first kWh block is cheapest, each block above costs more. Add rows to match your bill exactly.
Monthly bill (energy part)
$0.00
$0
avg rate / kWh
$0
per year (x12)
0
kWh billed
0
tiers used
12-month view
Enter kWh for each month (prefilled with a typical seasonal pattern) to see the full-year cost under these tiers.
Yearly total under these tiers
$0.00 / year
0
kWh / year
$0
avg $ / month
-
costliest month
-
cheapest month
Month
kWh
Cost
Time-of-use: the same kWh costs more at peak times, less off-peak. Drag the slider to model shifting usage to cheaper hours.
Monthly cost (time-of-use)
$0.00
$0
peak part
$0
off-peak part
$0
if all flat @ avg
$0
shift 20% saves
Flat comparison uses the weighted average rate. "Shift 20% saves" shows the saving from moving 20% of usage from peak to off-peak.
Tap a device to fill typical wattage and daily hours. Wattages are typical values — always check your device label for the real number.
Sources for typical wattage: US DOE and ENERGY STAR product data; "avg" devices (fridge, AC) use compressor-equivalent hours, not 24/7. Treat presets as starting estimates.
Reverse mode: you set the monthly budget, the tool tells you how much energy — and how many hours of a device — that buys.
Your budget buys
0 kWh / month
0
kWh / day
0
hours / day
0
minutes / day
$0
budget / day
Compare an old device against an efficient replacement running the same hours — e.g. a 2000 W heater vs a 1200 W inverter model.
You save per year
$0.00 / year
0
kWh saved / yr
$0
old cost / yr
$0
new cost / yr
0%
reduction
Payback time = price difference of the new device ÷ yearly saving. Not financial advice.
Enter tariffs manually (they change often — no stale built-in database) and compare the same usage side by side. Add up to 6 rows.
Core formulas.kWh = watts ÷ 1000 × hours · cost = kWh × tariff · month = day × 30 · year = day × 365. Tiered slabs apply cumulative caps: each block charges only the kWh inside it. Time-of-use splits kWh by the peak fraction you set. Budget reversal inverts the chain: kWh/month = budget ÷ tariff, then hours = kWh/day × 1000 ÷ watts.
Why 30 and 365? Bills use calendar months (28–31 days). Using a fixed 30-day month and 365-day year keeps daily/monthly/yearly figures mutually consistent, at the cost of ±3% vs any single calendar month. This convention is stated so you can adjust.
Device presets. Typical wattages are anchored to US DOE and ENERGY STAR product data. Devices that cycle (fridge, AC) use compressor-equivalent hours rather than 24/7 — noted on each preset. Your label is always the better number.
Honest limitations
What this tool does not model. Real bills add fixed supply charges, taxes, meter fees, and sometimes demand charges — the energy part shown here is a floor, not your full bill. Label wattage is a maximum or typical draw: motors surge at startup, thermostats cycle heaters, electronics vary with load, so real consumption differs. Some utilities define tiers per day rather than per month. Tariffs change frequently, which is why this tool asks you to type them in instead of shipping a database that would go stale. Results are estimates for planning, not financial advice.
Scope boundaries
Where this tool stops (by design).
Unit conversion only (kWh ↔ joules ↔ BTU, no prices) → energy unit converter territory.
Appliance database depth (dozens of devices, standby presets, bill slab builder) → appliance-focused calculator territory.
EV charging economics (battery kWh, charging losses, vs-gas) → EV charging cost calculator territory.
This tool owns the tariff layer: flat rates, tiered slabs, time-of-use, budget reversal, efficiency swaps, and tariff comparison.
Frequently asked questions
How do I calculate the energy cost of an appliance?+
Multiply watts by hours to get watt-hours, divide by 1,000 for kWh, then multiply by your tariff: cost = (watts / 1000) x hours x tariff. Example: a 1500 W heater running 2 hours at $0.15/kWh uses 3 kWh and costs $0.45.
How much does 1,000 watts cost per hour?+
1,000 watts for one hour is exactly 1 kWh. At $0.15/kWh that is $0.15; at $0.30/kWh it is $0.30. Enter 1000 W and 1 hour in the Quick tab to see it with your own tariff.
What is the difference between kW and kWh?+
kW (kilowatt) is power, the rate at which energy is used. kWh (kilowatt-hour) is energy, power multiplied by time. A 1 kW device running for 1 hour consumes 1 kWh. Electricity bills charge per kWh, not per kW.
How do tiered (block) electricity rates work?+
Your first block of kWh is billed at the cheapest rate, and each additional block costs more. Example: 250 kWh with slabs 0-100 at $0.10, 101-200 at $0.15, and 201+ at $0.25 costs $10 + $15 + $12.50 = $37.50. The Tiers tab replicates your exact slabs.
How does time-of-use pricing change my cost?+
The same kWh costs more during peak hours and less off-peak. Example: 100 kWh split 60% peak at $0.22 and 40% off-peak at $0.08 costs $13.20 + $3.20 = $16.40. Shifting usage to off-peak hours is the main saving lever.
How do I convert a monthly budget into kWh or hours per day?+
Divide your monthly budget by the tariff to get kWh per month, divide by 30 for kWh per day, then convert to hours: hours = kWh/day x 1000 / watts. Example: $50/month at $0.20/kWh with a 1200 W device allows 6.94 hours per day. The Budget tab does this instantly.
Is this the same as an energy unit converter?+
No. Energy unit converters translate between units (kWh, joules, BTU) without prices. This tool converts energy into money: flat tariffs, tiered slabs, time-of-use pricing, budget reversal, efficiency comparisons, and tariff comparison.
Does this tool calculate lighting costs?+
Only roughly, through the device presets. For lighting-specific planning with lumens, lux, and room layouts, a dedicated lighting calculator is the better tool.
How is this different from an appliance energy calculator?+
Appliance-focused calculators are built around a deep device database with standby presets. This tool is tariff-first: flat rates, tiered slabs, time-of-use pricing, budget reversal, efficiency swaps, and country tariff comparison in one place.
Why is my real bill higher than this calculation?+
This tool models energy cost only. Real bills add fixed supply charges, taxes, meter fees, and sometimes demand charges. Devices also rarely run at label wattage constantly: air conditioners cycle, refrigerators cycle, and TVs vary with brightness. See the honest limitations section.
How much does it cost to run an air conditioner per hour?+
Roughly watts / 1000 x tariff. A 1500 W unit at $0.15/kWh costs about $0.225 per hour while the compressor is running. Real air conditioners cycle on and off, so applying a 50-70% duty factor gives a better estimate.
How much does a refrigerator cost per month?+
A fridge does not run 24/7, so use its average equivalent hours, often 6-10 hours per day at rated watts. Example: 150 W x 8 h = 1.2 kWh/day = 36 kWh/month, about $5.40 at $0.15/kWh.
Can I compare electricity tariffs between countries?+
Yes. The Compare tab takes your monthly kWh and any set of tariffs you enter manually, then shows side-by-side costs. Tariffs change often, so this tool deliberately uses manual input instead of a stale built-in database.
Does the label wattage equal actual consumption?+
Not always. Labels show maximum or typical draw: motors surge at startup, heaters cycle with thermostats, and electronics vary with load. A plug-in power meter gives the true number; treat label-based results as estimates.
What is standby (phantom) load, and does it matter?+
Devices in standby still draw power, often 1-10 W each. Ten devices at 5 W draw 50 W continuously, about 36 kWh/month or $5.40 at $0.15/kWh. The Devices tab includes an always-on preset so you can model this.
Is my data sent anywhere?+
No. Everything runs locally in your browser: no accounts, no uploads, and no tracking of your inputs. Your numbers never leave your device.
We use cookies and third-party services (including Google AdSense) to personalize content, analyze traffic, and serve relevant ads. By clicking "Accept", you consent to our use of cookies as described in our Privacy Policy.
Report an issue
2 taps, no typing needed — diagnostics are sent automatically.