Watts to kWh: How to Convert Watts to Kilowatt-Hours
Trying to decipher your quarterly energy bill, or wondering whether a portable battery will keep your camp fridge running all weekend? You aren’t the only one. Energy labels love throwing out numbers like 1,800W, 2.4 kW and 300 Wh. Your power bill only cares about one unit, the kilowatt-hour (kWh), and every figure on the sticker lands there eventually.
None of this takes more than two steps of maths. Below, we’ll use those two steps on running costs across Australian homes, and on sizing power gear for a blackout or an off-grid caravan trip.
Quick Answer
Converting watts to kilowatt-hours (kWh) takes two steps. Multiply the wattage by the hours it runs, then divide by 1,000.
kWh = Watts × Hours ÷ 1,000
Example: A 2,000W split-system air conditioner running for 4 hours uses:
(2,000 × 4) ÷ 1,000 = 8 kWh. At 35c/kWh, that session costs $2.80.
What Is the Difference Between Watts and Kilowatt-Hours?
Both numbers sit on the same label, but they don’t measure the same thing. Watts are the rate, how fast electricity is being drawn. Kilowatt-hours are the total, the energy you’ve actually used.
Watts Measure Power
Think of watts (W) as the speedometer for whatever’s plugged in. The reading tells you how fast a device is drawing energy right now. A kettle on the bench draws 0 watts while it sits idle. Flick the switch and it jumps straight to 2,200W.
Kilowatt-Hours Measure Energy Consumption
Kilowatt-hours (kWh) are the odometer in that comparison, since they count the total energy you’ve actually used. If you run a 1,000-watt appliance at full tilt for an hour, that’s exactly one kilowatt-hour of energy on the meter.
Why Watts and kWh Are Used Differently
Gear gets labelled in watts so you can tell, before you hand over any money, whether an inverter will handle the load and whether the current draw in amps will stay under your circuit breaker’s limit. Your bill is answering a different question altogether — it’s worked out in kilowatt-hours, since that’s what builds up. The same distinction matters when comparing a portable power station, because output is rated in watts while storage capacity is rated in Wh or kWh.
How Do You Convert Watts to kWh?
Once you know the rated draw and how long the thing runs, the sum takes seconds.
Watts to kWh Formula
Take the power figure and multiply it by the hours in use. Divide by 1,000 and you've turned watt-hours into kilowatt-hours:
Energy (kWh) = Power (W) × Time (hours) ÷ 1,000
How to Convert kWh to Watts
The formula runs backwards, too, but you need to know the time period over which the energy was used. Multiply the energy in kWh by 1,000, then divide by the number of hours:
Power (W) = Energy (kWh) × 1,000 ÷ Time (hours)
For a household electricity bill, the result is the average power used over that period, not the instantaneous power draw of an appliance.
Watts to kWh Calculation Examples
Three worked examples:
Living room fan (60W) running overnight (8 hours):
(60W × 8h) ÷ 1,000 = 0.48 kWhAir fryer (1,500W) cooking dinner (30 minutes / 0.5 hours):
(1,500W × 0.5h) ÷ 1,000 = 0.75 kWhEspresso machine (1,800W) pulling shots (10 minutes / ~0.17 hours):
(1,800W × 0.17h) ÷ 1,000 = 0.306 kWh ≈ 0.31 kWh
Watts to kWh Conversion Table
Appliance | Rated Power (Watts) | Indicative Usage Time | Total Energy (kWh) |
Phone Charger | 20W | 2 hours | 0.04 kWh |
12V Caravan Fridge | 45W | 24 hours (duty cycle ~35%) | ~0.38 kWh |
LED Downlight (x4) | 40W total | 5 hours | 0.20 kWh |
Laptop Workstation | 85W | 8 hours | 0.68 kWh |
Microwave Oven | 1,200W | 15 minutes (0.25 h) | 0.30 kWh |
Electric Kettle | 2,200W | 6 minutes (0.1 h) | 0.22 kWh |
Column Oil Heater | 2,400W | 4 hours (thermostat regulated ~60%) | ~5.76 kWh |
How Many kWh Do Common Appliances Use?
By now you’ve probably noticed two numbers doing all the work: the rated wattage, and the hours the thing actually runs. For anything that cycles on and off, those hours are really the duty cycle in disguise. In most homes the energy goes into heating, cooling, refrigeration and cooking — chargers and small electronics barely show up by comparison.
Kitchen and Household Appliances
In many Aussie kitchens, heating elements are among the higher-draw loads. A 2,200W kettle shows why wattage alone can mislead: if it runs for about 3 minutes, it uses roughly 0.11 kWh. An older French-door fridge works differently: a model drawing 150W to 200W while its compressor runs could use roughly 1.5 to 2.2 kWh across 24 hours, depending on its efficiency, settings, ambient temperature and duty cycle.
Camping and Caravan Appliances
Out on the track, a 12-volt compressor fridge (an Engel or a Dometic 65L, say) only pulls its 35W to 60W while the motor’s going. The compressor keeps cycling on and off rather than running flat out, so in temperate weather you’d expect it to use around 350Wh to 500Wh (0.35 to 0.5 kWh) a day. Park in unshaded outback heat, though, and it climbs quickly. A 12V water pump (60W, used every so often) and camp lighting (15W for 4 hours) round out the picture. Altogether, a standard off-grid setup comes to about 0.6 to 0.8 kWh a day. Working out how much power you need for camping starts with these daily Wh or kWh totals rather than appliance wattage alone.
Electronics and Portable Devices
Personal devices barely register on the electricity meter. Fast-charge an iPhone and it’ll pull 20W to 30W for about an hour, a mere 0.025 kWh all up. The Starlink Mini is the misleading one: it only sips 25W to 40W, yet an evening of remote work and streaming quietly adds up to roughly 0.3 kWh.
How Much Does It Cost to Run an Appliance?
Across Australian states you’ll typically pay somewhere between $0.26 and $0.45 per kWh, and where you land in that band comes down to your distribution network and your tariff, which might be flat or time-of-use.
Electricity Cost Formula
To work out what an appliance adds to your next bill, you need exactly one multiplication: energy use in kWh, times your tariff rate.
Running cost = Energy (kWh) × Tariff rate per kWh
Calculate Running Costs From Watts and Usage Time
Or go straight from wattage, run time and your electricity rate:
Cost = Watts × Hours ÷ 1,000 × Rate per kWh
Take a 1,500W electric bar heater in a chilly Melbourne July:
Per hour: (1,500 ÷ 1,000) × $0.35 = $0.525/hour
Overnight (8 hours): 1.5 kW × 8 h × $0.35 = $4.20 per night
Over a full month (30 days): $4.20 × 30 = $126.00 added to your bill.
How Can You Use Watts and kWh to Choose a Portable Power Station?
Work out your requirements in kWh first. Then you’re much less likely to run short of power on the road, or to sit in the dark through a storm.
Add Up the kWh Your Devices Need
Work out what each device uses in a day, then add the figures up. A camp on an unpowered site might look like this:
45W 12V fridge (24 hours at 35% duty cycle): 380 Wh (0.38 kWh)
Two phone charges and one tablet: 70 Wh (0.07 kWh)
LED camp strip lights (4 hours at 15W): 60 Wh (0.06 kWh)
Morning coffee via travel pod machine (1,400W for 5 mins): 115 Wh (0.115 kWh)
Total Daily Need: ≈ 625Wh(0.625kWh)
Check Both Battery Capacity and Power Output
When you're shopping, two numbers matter rather than one. Capacity and continuous output are separate specs, so what appliances a portable power station can run depends on both the stored energy and the load at any one time.
Continuous Output (Watts): The inverter's muscle. A 500W pack won't run a 1,800W hair dryer or a 1,200W sandwich press, however big the battery inside is.
Storage Capacity (Wh or kWh): The fuel tank. A 1,000Wh battery has a theoretical runtime of 1.25 hours at a steady 800W load, but usable capacity, conversion losses and standby consumption make real-world runtime shorter. Check the product specifications and allow a practical margin.
Match Battery Capacity to Your Usage Scenario
What a weekend in a ute canopy asks of a battery is nothing like what a caravan running a fridge and lights asks, and a home backup plan covering a few hours of outage lands somewhere else again. Battery size should match the way you actually use power.
Short weekend getaways, ute canopies, and emergency backup
For short trips or basic home backup, the EcoFlow DELTA 3 Classic Portable Power Station is a practical fit. Its 1,024Wh capacity can cover a 12V fridge, phone charging, lights, a laptop, Wi-Fi router, or a few essential household appliances during a short outage. The 1,800W AC output also gives enough headroom for higher-draw items such as a suitably rated kettle or electric frypan, as long as you manage one major load at a time.
Extended touring, caravans, and off-grid travel
For longer trips or higher daily demand, the EcoFlow DELTA 3 Max Plus Portable Power Station gives you more room to work with. Its 2,048Wh capacity and 3,000W AC output are better suited to caravans, 4WD touring, power tools, induction cooking, or multiple devices running across the day. It is a better match when you need more than lights, phones, and a fridge, especially if you also plan to recharge from solar while travelling.
Conclusion
Working out what an appliance costs to run takes one sum — watts times hours, divided by 1,000 — and the mystery goes out of both the power tag and the bill. Your daily kWh figure takes you a step further, telling you how much portable battery a trip out bush really needs, and how much reserve carries the house through a weather-driven grid dropout. Wherever you are in the country, that’s how you end up with the power you need rather than the power you hoped for.
FAQ
How much electricity does 1000 watts consume in 1 hour?
A 1,000-watt appliance running at full power for one hour uses exactly 1 kilowatt-hour (1 kWh) of energy.
How long does a 1 kWh battery last?
It depends on what you’re running. With a typical 70W camping fridge, you’ll get roughly 30 to 35 hours out of a 1 kWh (1,000Wh) battery. That already allows for 85% inverter efficiency and a 35–40% compressor duty cycle. Put a 1,000W microwave on it continuously, though, and you’re down to about 50 minutes.
Is 2000 watts the same as 2 kW?
They’re the same quantity, written two ways. Kilo is the metric prefix for a thousand, so 2,000 watts is exactly 2 kilowatts (kW).
How much does a 2000W heater use per hour?
At full power, a 2,000W heater chews through 2 kWh of electricity for every hour it runs. If it has a thermostat, though, the element switches off once the room warms up. Real-world use often drops to around 1.2 to 1.5 kWh per hour.
How much does it cost to run a 1500 W electric heater for 24 hours?
A 1,500W heater left running for 24 hours straight consumes 36 kWh. At $0.35 per kWh, that’s about $12.60 a day.