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Convert watts to kilowatt hours instantly. Calculate exact energy consumption and electricity cost for any device — daily, monthly, and yearly.
My neighbour Rajan was convinced his new LED TV was responsible for his skyrocketing electricity bill. He had switched from an old CRT to a 55-inch LED last summer and assumed that was the culprit. When we sat down with this kWh calculator and put in every device in his house, the result was eye-opening: his TV was costing him just ₹72 a month. His 10-year-old 1.5-ton AC running 8 hours a day was costing him ₹3,024 a month. His geyser, used for 30 minutes every morning, was adding another ₹900. The TV had nothing to do with it. Three minutes with a kWh calculator gave him more insight into his electricity bill than 3 years of guessing had.
This calculator converts watts to kilowatt hours (kWh) for any device, shows you the exact energy cost in your local currency, and breaks down consumption device by device. Whether you're in India paying ₹8/unit, the UK at £0.25/kWh, or the US at $0.16/kWh — just select your country, enter your devices, and get instant clarity.
The conversion from watts to kilowatt-hours is one of the most useful calculations in household energy management. Here's the complete formula:
Worked example — 1.5 Ton AC in India: A 1.5 ton AC uses approximately 1,500 watts. Running it 8 hours/day: kWh = (1500 × 8) ÷ 1000 = 12 kWh/day. At ₹8/unit: Daily cost = 12 × ₹8 = ₹96. Monthly cost = ₹96 × 30 = ₹2,880. Annual cost = ₹96 × 365 = ₹35,040. That one AC accounts for ₹35,040/year in your electricity bill.
kW (kilowatt) is power — how fast energy is being used right now. kWh (kilowatt-hour) is energy — the total amount used over time. Think of kW as speed and kWh as distance. A 2kW appliance running for 3 hours consumes 6 kWh — the same as 6 units on your electricity bill.
1 unit of electricity = 1 kWh (kilowatt-hour). When your bill says you used 200 units last month, that means you consumed 200 kWh of energy. In India, the rate per unit varies by state and consumption slab — typically ₹5–₹10/unit. Most urban households pay ₹7–₹9 per unit in the 200–400 unit slab.
Choose your country from the dropdown — the local electricity rate auto-fills. You can override this with your exact rate from your bill. India's rate is set to ₹8/kWh by default, which is typical for urban households in the 200–500 unit slab.
Enter how many watts your device uses (check the label on the device or the sidebar reference list) and how many hours per day you use it. Click "Add Another Device" to track multiple appliances simultaneously.
Toggle between Daily, Monthly, or Yearly to see your kWh and cost in the timeframe most useful to you. Monthly is the default since most people think in monthly electricity bills.
See total kWh, energy cost in your currency, annual projection, device-by-device breakdown table, and a bar chart showing which devices are consuming the most energy — so you know exactly where to focus energy-saving efforts.
A typical Bangalore family with 2 ACs (1.5 ton each, 8hr/day), refrigerator (24hr), washing machine (1hr/day), 6 LED bulbs (5hr/day), TV (4hr/day), and geyser (0.5hr/day). Total: approximately 42 kWh/day = 1,260 kWh/month. At ₹8/unit: ₹10,080/month. Using this calculator to identify that the 2 ACs alone account for 72% of the bill often prompts families to install a 5-star rated AC, set the temperature to 24°C instead of 18°C, and use ceiling fans alongside — potentially saving ₹2,500–₹3,500/month.
A UK couple using an electric space heater (2kW, 6hr/day), electric oven (2kW, 1hr/day), washing machine (2kWh/cycle, once daily), laptop (45W, 8hr/day), TV (80W, 4hr/day), and LED lighting (100W total, 8hr/day). Monthly kWh: approximately 480 kWh. At £0.25/kWh: £120/month. The calculator immediately shows the space heater accounts for 75% of total consumption — prompting the switch to a heat pump or better insulation as a cost-saving priority.
A Dubai resident with a 2-ton central AC running 16 hours/day (summer), refrigerator 24hr, dishwasher 1hr, 4 LED lights 8hr, TV 3hr. Monthly: approximately 1,120 kWh. At AED 0.38/kWh: AED 425.6/month. The kWh calculator shows the AC alone uses 1,024 kWh of the 1,120 kWh total — 91% of the bill. Raising the thermostat from 20°C to 24°C reduces AC consumption by approximately 20%, saving AED 85/month.
A freelancer working from home with a desktop PC (200W, 8hr), 2 monitors (25W each, 8hr), 1 ton AC (900W, 8hr), LED desk lamp (10W, 8hr), router (15W, 24hr), and phone charger (20W, 2hr). Monthly: approximately 250 kWh. At ₹8/unit: ₹2,000/month just for the home office. Switching to a laptop (50W) instead of desktop saves approximately 40% of compute power cost — ₹300/month, ₹3,600/year — just from that one hardware change.
Every 1°C decrease in AC temperature increases energy consumption by 6–8%. Setting your AC to 24°C instead of 18°C saves approximately 36–48% on AC electricity cost. Use ceiling fans alongside to feel cooler at a higher thermostat setting — fans use only 75W vs 1500W for an AC.
A 5-star 1.5 ton AC uses approximately 840 units/year vs 1,200 units for a 2-star model — saving 360 units/year. At ₹8/unit, that's ₹2,880/year in savings. The premium for a 5-star AC pays for itself in 2–3 years and continues saving for 10+ years.
TVs, set-top boxes, chargers, and gaming consoles on standby consume 2–10W continuously — 24 hours a day. 10 devices at 5W standby = 50W × 24hr = 1.2 kWh/day = 36 kWh/month. At ₹8/unit: ₹288/month from devices doing nothing. Use smart power strips or simply switch off at the socket.
Replacing ten 60W incandescent bulbs with 10W LED bulbs saves 500W per hour of use. At 6 hours/day for 30 days: 500W × 6hr × 30 = 90 kWh/month saved. At ₹8/unit: ₹720/month saving from lighting alone. LED bulbs also last 15–20× longer, reducing replacement costs.
A 2kW geyser running 45 minutes twice daily = 3 kWh/day = 90 kWh/month = ₹720/month. Installing a solar water heater (₹15,000–₹25,000) eliminates this cost entirely — payback period of 2–3 years, then 15+ years of free hot water. Alternatively, using a geyser timer prevents it running longer than needed.
Keep the refrigerator at 3–4°C and freezer at -18°C — colder wastes energy. Ensure door seals are tight (a leaky seal adds 10–25% to fridge consumption). Don't put hot food directly in — cool it first. Keep the fridge 75% full for efficiency. A well-maintained modern refrigerator uses half the electricity of a 10-year-old model.
Many states in India and countries globally offer time-of-use (TOU) tariffs where electricity is cheaper during off-peak hours (typically 11 PM – 6 AM). Running washing machines, dishwashers, and EV charging during these hours can reduce electricity costs by 20–40%. Check with your local utility for TOU availability.
Your electricity bill shows units used (kWh) and total cost. Track the kWh number month over month — not just the cost, which fluctuates with tariff slabs. A consistent kWh count with a rising bill means a tariff increase. Rising kWh means a consumption change. Use this calculator monthly to identify which device changed its usage pattern.
Divide watts by 1,000 to get kilowatts (kW), then multiply by the number of hours used. Formula: kWh = (Watts × Hours) ÷ 1,000. Example: a 1,500W AC running for 8 hours = (1500 × 8) ÷ 1000 = 12 kWh. This 12 kWh is what gets recorded on your electricity meter and billed as 12 units. At ₹8/unit in India, that's ₹96 for one day of AC usage.
In India, the cost per kWh (per unit) varies by state and consumption slab. Typical ranges in 2025: 0–100 units: ₹3.50–₹5.50/unit (subsidised lifeline slab). 101–200 units: ₹5–₹7/unit. 201–400 units: ₹7–₹9/unit. 401–500 units: ₹8–₹10/unit. Above 500 units: ₹9–₹12/unit. Urban households consuming 200–500 units typically pay ₹7–₹9/unit. Check your actual bill for the exact rate applicable to your slab — the rate increases as your consumption rises, which is why large households pay a higher per-unit rate.
In Indian homes during summer, air conditioners are overwhelmingly the biggest consumers — a single 1.5 ton AC running 8 hours/day uses 12 kWh/day, accounting for 50–70% of a typical household's electricity bill. In winter or all-year households, water heaters (geysers) are the second biggest consumers. In Western countries with electric heating, space heaters and heat pumps dominate. Use this kWh calculator to enter all your devices and see the exact percentage breakdown — the results often surprise people because perception rarely matches reality.
A modern energy-efficient refrigerator (BEE 5-star rated, 250 litre) uses approximately 90–120 kWh per month, running continuously 24 hours a day. An older or less efficient model may use 150–200 kWh/month. At ₹8/unit in India, a modern fridge costs ₹720–₹960/month; an old inefficient model costs ₹1,200–₹1,600/month. The difference — ₹480–₹640/month — is ₹5,760–₹7,680/year. This is why upgrading an old refrigerator to a 5-star model often pays for itself in 3–4 years purely from electricity savings.
The wattage on an appliance label (e.g. "1500W") tells you the power draw — how much electricity it consumes per hour if running at full capacity. kWh is what your electricity meter actually measures — it accounts for how long the appliance runs. A 1500W appliance running for 1 hour uses 1.5 kWh. Running for 10 minutes uses 0.25 kWh. The meter (and your bill) only counts kWh, not watts directly. This is why a high-wattage appliance used briefly (like a microwave at 1100W for 5 minutes = 0.09 kWh) costs far less than a lower-wattage appliance used for hours (a 150W fridge running 24hr = 3.6 kWh/day).
⚠️ Disclaimer: kWh calculations are estimates based on entered device wattage and usage hours. Actual consumption varies with appliance efficiency, usage patterns, and ambient conditions. Electricity tariff rates are approximate — verify with your utility provider. This tool is for educational and planning purposes only.