Electricity Bill, kWh & Tariff Guides

How to Calculate Electricity Cost from Watts and kWh

Imported guide · Source date 2026-09-07 · 5 min read

To calculate electricity cost from watts, divide watts by 1,000, multiply by hours used, then multiply by your price per kWh. Use average power or account for duty cycle once when a heater or compressor cycles.

Calculate watts or kWh cost →

Electricity cost formula: the quick answer

For example, 1,000 W running continuously for one hour uses 1 kWh: at ₹8/kWh it costs ₹8. A 400 W device for three hours uses 1.2 kWh and costs ₹9.60 at the same illustrative rate. Watts measure power; “watts per hour” is not the energy unit on your electricity bill.

Use the watts and kWh cost calculator to change the numbers. For a fridge or freezer, the annual energy-label calculator avoids guessing compressor hours.

Every electricity bill in the world works the same way: your meter counts kilowatt-hours, and your supplier charges you a price for each one. Once you understand that single sentence, you can work out the running cost of anything in your home — an air conditioner, a fridge, a gaming PC, an electric car — with nothing more than a rating plate and a calculator.

This guide walks through the whole process, then covers the mistakes that make most homemade estimates badly wrong.

Step 1: Find the appliance's wattage

Wattage is the rate at which a device consumes electricity. There are four places to look, in order of reliability:

• A plug-in energy meter. The gold standard. It measures what the appliance actually draws right now, including the standby draw and the effect of thermostat cycling. They cost very little and pay for themselves the first time they find a forgotten always-on load.
• The energy label. For fridges, washing machines and dryers, the annual kWh figure comes from a standardised test cycle and is far better than a nameplate estimate.
• The rating plate. Usually on the back or underside. If it shows amps instead of watts, multiply amps by your supply voltage (230 V in most of the world, 120 V in North America).
• A typical value. Every calculator on this site ships with realistic presets, which are fine for a first estimate.

Step 2: Convert watts into kilowatt-hours

A kilowatt-hour, or 'unit', is 1,000 watts drawn for one hour. The conversion is a single line of arithmetic:

A 1,500 W heater running three hours uses 1.5 × 3 = 4.5 kWh. A 9 W LED bulb running the same three hours uses 0.027 kWh. Same formula, wildly different answers — which is precisely why the big loads deserve your attention first.

Step 3: Apply your real tariff

Take the unit rate from your bill, not from a news headline. Use the all-in rate that includes taxes, levies and distribution charges, because that is what you actually pay for the next unit you consume.

Continuing the example: 4.5 kWh at $0.17 is $0.77 for that three-hour heating session. Run it every evening for a month and you are at about $23.

Step 4: Scale it to a month and a year

Hourly costs are psychologically misleading. Cents per hour feels like nothing; the same figure expressed per year is what changes behaviour. Always finish the calculation at annual scale:

The four mistakes that ruin most estimates

1. Treating nameplate watts as constant draw

This is the big one. Multiplying a fridge's 150 W nameplate by 24 hours gives 3.6 kWh a day. The real figure is closer to 1.2 kWh, because the compressor only runs about a third of the time. Overestimating by 3× makes every conclusion you draw from the number worthless.

2. Confusing power supply rating with consumption

An 850 W PC power supply does not consume 850 W, and a 3,000 W kettle does not consume 3 kWh unless it runs a full hour — it runs for three minutes and uses 0.15 kWh. Rated capacity is a ceiling, not a measurement.

3. Ignoring always-on devices

A 25 W set-top box left on permanently uses 219 kWh a year. A 1,600 W hair dryer used ten minutes a day uses 97 kWh. The device that feels powerful costs less than half as much as the one you never think about. Time on beats watts almost every time.

4. Using an average tariff on a tiered plan

In many markets, unit prices rise in slabs as monthly consumption increases. If you are already in the top slab, every unit you save is worth the top-slab rate, not the average — which means efficiency measures pay back faster than a naive calculation suggests.

Worked example: a full household

Here is a realistic mid-size home, calculated appliance by appliance:

Two things jump out. The air conditioner is 60% of the bill, so that is where any serious saving has to come from. And the router and set-top box — 37 W of quiet, permanent draw — cost more than the washing machine alone.

Do it automatically

Every calculation above is built into our free tools. Start with the appliance energy cost calculator for a single device, or the electricity bill calculator to model your whole home and rank your biggest drains.

Calculate it yourself

Imported source date: 2026-09-07. Review details have not been independently verified.

How to Read an Electricity Bill and Check the Calculation

Imported guide · Source date 2026-09-07 · 6 min read

Check an electricity bill by separating meter readings, variable energy charges and fixed fees. Subtract the opening kWh reading from the closing reading, apply any stated multiplier, then price the units at the correct tariff or slabs.

Price the kWh shown on your bill →

Calculate an electricity bill from a meter reading

Subtract the previous cumulative kWh reading from the current one. For example, 12,780 − 12,450 = 330 kWh. At an illustrative flat ₹8/kWh, the energy charge is ₹2,640 before any separately charged fixed fees, taxes or credits. Use the meter multiplier if your bill specifies one.

On a slab tariff, split those 330 units across the published slabs instead of pricing every unit at the highest rate. A time-of-use meter may have separate registers: calculate each register’s difference at its matching tariff. This example is not an official state tariff.

Price measured usage with the direct-kWh calculator, or estimate where those units went using the appliance-by-appliance bill calculator.

Electricity bills are designed by engineers and printed by accountants, which is why they are almost universally confusing. But underneath the layout differences, every bill in the world is built from the same handful of components. Once you can identify them, you can check whether you are being charged correctly and work out which parts of the bill you can actually influence.

The two things you are always paying for

Every electricity bill splits into energy charges and fixed charges.

Energy charges are what you pay for the units you consumed. This is your consumption multiplied by a rate per kilowatt-hour. It varies with how much you use, and it is the part you can reduce by using less.

Fixed charges are what you pay for being connected at all — the standing charge, service charge, meter rent, or whatever your supplier calls it. You pay these even if you use nothing. Reducing consumption does not reduce them.

Meter readings

Your bill shows an opening and closing meter reading. The difference between them is your consumption in units.

Look for a letter code next to each reading. A or Actual means someone read the meter or it reported automatically. E or Estimated means the supplier guessed based on your history. Estimated readings are the single most common cause of a shockingly wrong bill — and the easiest to fix, by submitting a real reading.

Which digits to read

On a digital meter, read the numbers before the decimal point and ignore anything in red or after the decimal. On a dial meter, read each dial left to right, taking the lower number when a pointer sits between two digits.

The unit rate

This is the price of one kilowatt-hour. It is the number you need for every calculator on this site, and it is the number most people get wrong when estimating appliance costs — usually by using a headline figure from the news rather than the rate on their own bill.

Find the line that says something like "Energy charge" or "Units @". It will show a rate and a quantity. Divide the energy charge by the units to check the rate matches what you expect.

Slab or tiered tariffs

Many markets, India especially, charge different rates for different bands of consumption. The rate rises as you use more, so the marginal cost of your last hundred units can be double the cost of your first hundred.

Two consequences follow. First, your average rate is not your marginal rate — in the example above the average is ₹6.43 but the next unit you consume costs ₹8.40. Second, saving units saves them at the top slab rate, which makes efficiency measures worth substantially more than the average rate suggests.

Time-of-use tariffs

A time-of-use plan can have cheap and expensive windows. The exact times and rates are supplier-specific: use the schedule in your tariff document, not a generic overnight timetable. Include any daytime price increase when evaluating a switch.

• Illustrative off-peak window: 00:00–07:00. Often a third to a half of the peak rate. Run the dishwasher, washing machine, EV charging and water heating here.
• Standard daytime. The baseline rate for most consumption.
• Illustrative peak window: 16:00–20:00. The most expensive window, and unfortunately when most households cook and heat.

The other lines

Beyond rate and consumption, bills carry a collection of adjustments that vary enormously by country.

Working out your real per-unit cost

For estimating appliance running costs, you want your all-in rate — what one more unit actually costs you, including everything that scales with consumption.

Exclude arrears, deposits, one-off adjustments and fixed fees when deriving an average variable rate. If taxes are already included in the unit rate, do not add them twice. For a saving on a slab tariff, use the rate of the units actually avoided; the average rate may not represent that marginal cost.

Common billing problems and what causes them

A bill much higher than usual

Check the reading code first. If it says estimated, submit an actual reading and ask for a rebill. If the reading is actual, compare units consumed against the same month last year — if units are similar but cost jumped, the rate changed. If units jumped, something in the house changed.

A bill much lower than usual, followed by a huge one

Classic sign of a run of underestimated readings followed by a catch-up actual reading. The total is usually correct; the distribution across months was not. Most suppliers will spread a catch-up charge if you ask.

Charges after you moved out

Always take a photograph of the meter on the day you leave, with the reading legible. It is the only evidence that settles the dispute.

A quick monthly check

Once a month, note your meter reading on the same date. Divide the difference by the days elapsed to get your daily average. A sudden change in that daily average — with no change in weather or occupancy — usually means a failing appliance, an immersion heater left on, or a water pump cycling on a leak.

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Imported source date: 2026-09-07. Review details have not been independently verified.

Watts, Volts, Amps and Kilowatt-Hours — Explained Simply

Imported guide · Source date 2026-08-20 · 10 min read

Watts measure how fast you use electricity. Kilowatt-hours measure how much you used. Confusing the two is why most energy estimates go wrong.

Almost every mistake in home energy calculation comes from confusing two things: the rate at which an appliance uses electricity, and the total amount it used. They have different units, they are measured differently, and only one of them appears on your bill.

The water analogy

Electricity behaves enough like water in a pipe that the analogy is worth using.

• Volts are the water pressure — how hard the electricity is being pushed.
• Amps are the flow rate — how much is moving through the pipe.
• Watts are the power — pressure times flow, the rate at which energy is being delivered.
• Kilowatt-hours are the total volume delivered — power multiplied by time.

A tap running hard for one second delivers less water than a tap trickling for an hour. Same idea: a 2,000 W kettle running three minutes uses less energy than a 20 W router running all week.

The formulas you actually need

That is the whole toolkit. Everything else is a variation.

Watts versus kilowatt-hours

This is the distinction that matters most.

You are never billed for watts. You are billed for kilowatt-hours, which is why a high-wattage appliance used briefly can cost less than a low-wattage one left on.

What a 'unit' means

In most countries, one unit of electricity is exactly one kilowatt-hour. If your bill says you used 340 units, you used 340 kWh. The terms are interchangeable, and utilities use them inconsistently on the same document.

Converting between them

Amps to watts

Multiply amps by volts. A 10 A appliance on a 230 V supply draws 2,300 W. The same 10 A appliance on a 120 V supply draws 1,200 W — which is why appliance ratings differ between countries.

Horsepower to watts

One horsepower is 746 W of output. But motors are not perfectly efficient, so a 1 HP motor draws more than 746 W from the supply — typically 850 to 1,000 W depending on efficiency.

BTU to watts

Air conditioners are often rated in BTU per hour of cooling, which describes output, not consumption. Divide BTU/h by 3.412 to get watts of cooling, then divide by the efficiency ratio to get electrical input.

Tonnes of refrigeration

One tonne of cooling is 12,000 BTU/h, or about 3.5 kW of cooling capacity. A 1.5-tonne air conditioner delivers 18,000 BTU/h and typically consumes 1,200 to 1,700 W of electricity to do it.

Reading an appliance label

Rating plates carry more information than people use. A typical label might read: 230V ~ 50Hz 6.5A 1500W.

• 230V — the supply voltage it expects.
• ~ — alternating current.
• 50Hz — supply frequency.
• 6.5A — current drawn at full load.
• 1500W — power consumption at full load.

If the label gives only volts and amps, multiply them. Note that 230 × 6.5 = 1,495, close to the stated 1,500 W — labels round.

Why your appliance never draws exactly its rated power

Three reasons, and all three make real consumption lower than the label suggests.

• Duty cycling. Anything with a thermostat runs in bursts. See our guide on duty cycle for the full explanation.
• Partial load. A vacuum cleaner on a low setting, a fan on speed one, or a variable-speed motor all draw less than rated.
• Ratings are maximums. The number on the label is what the appliance can draw under worst-case conditions, not what it typically does.

Quick reference

That last row is worth remembering on its own. Any device left running continuously uses 8.76 kWh a year for every watt it draws — the fastest way to price an always-on load in your head.

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Imported source date: 2026-08-20. Review details have not been independently verified.

Electricity Prices by Country: 2026 Reference Guide

Imported guide · Source date 2026-09-07 · 5 min read

Compare published electricity-price references available in 2026, with their actual observation periods. The US and GB references use 2026 periods; the Eurostat figures below cover the second half of 2025. These are not one synchronized global tariff or a quote for your home.

Calculate cost using your own unit rate →

Published electricity prices by country: dated references

The table separates source observations from the editable example rates in our calculators. Do not compare different currencies as if their numbers were equivalent, or treat different observation periods as a single world ranking. The 100 kWh column is simply each reported rate multiplied by 100, not a complete bill quote.

US source: EIA Electric Power Monthly, Table 5.6.A [4], June 2026 data released 26 August 2026, checked 7 September 2026. The US Total residential column is 18.34 cents/kWh, not the 14.48-cent all-sector average. EIA marks the estimates preliminary; an average revenue-per-kWh statistic is not your marginal retail unit rate.

GB source: Ofgem’s July–September 2026 publication [5]. The electricity reference covers standard-variable Direct Debit averages in England, Scotland and Wales and includes 5% VAT. The daily standing charge is separate; this does not describe every UK household or Northern Ireland.

European source: Eurostat electricity-price statistics [4] and the 5 May 2026 release [2], checked 7 September 2026. The figures cover household consumption of 2,500–5,000 kWh/year in the second half of 2025 and include taxes, levies and VAT. EU is not the same group as the euro area; the EU weighted average must not be labelled an Ireland or eurozone tariff.

How to compare countries without misleading yourself

• Match observation periods before making a time-series comparison.
• Keep local currencies separate unless you state an exchange-rate source and date.
• Check whether a reported price includes fixed charges, taxes, subsidies or a specific consumption band.
• Use the next-unit or time-of-use rate from your own bill for an extra appliance; a national statistical average is a different measure.

The examples used by a calculator do not automatically update to each newly published statistic above. Our default US $0.17/kWh and euro €0.285/kWh inputs remain labelled illustrative. Use your actual variable tariff, or deliberately enter a dated benchmark for a comparison.

Editable calculator defaults—not the published statistics above

UK reference: scope, date and standing charges

For 1 July–30 September 2026, Ofgem reports an average electricity unit rate of 26.11p/kWh and a 57.19p daily standing charge for standard-variable Direct Debit customers across England, Scotland and Wales, including 5% VAT. The equivalent gas figures are 7.33p/kWh and 29.04p/day. Source checked 7 September 2026: Ofgem’s period-specific publication [5].

These are not a fixed quote for every UK household. Northern Ireland has separate arrangements; fixed plans, prepayment and other payment methods can differ. The UK calculator selector uses this Great Britain electricity reference as an editable starting point. An EV off-peak deal is not the same as this standard-variable reference.

At the reference electricity price, 100 kWh costs £26.11 in variable energy charges. Thirty days of standing charges would add £17.157, making about £43.27 before any other adjustments. Do not allocate the full standing charge to each appliance, or add VAT again when it is already included.

Why the calculator defaults are not a cheapest-country ranking

A meaningful international ranking needs the same reporting period, tax treatment, consumption band and currency-conversion date. This calculator reference table does not satisfy that statistical comparison. We have removed the unsourced USD conversions and do not rank countries by the default inputs.

For a published national comparison, consult a dated statistical series such as Eurostat household electricity prices or the US EIA retail electricity series. Check the methodology and date before comparing it with an individual retail quote. We do not imply that those series verify every default shown here.

Use your own bill for appliance costs

• Find the variable price per kWh and note whether taxes are included.
• On a time-of-use plan, use the rate when the appliance actually runs, or a kWh-weighted blend.
• On a slab tariff, price savings using the units and bands actually avoided.
• Keep fixed connection charges separate from the cost of an extra appliance.
• For solar, consider the export credit you give up; own-generation electricity is not automatically free.

The electricity-bill guide explains meter readings and rate lines. Use the kWh cost calculator to price measured units, the UK EV charging calculator for battery top-ups, or the fridge energy-label calculator for annual use.

Carbon estimates are separate from price

The tools also carry fixed illustrative grid-carbon factors. They are not live, regionally granular emissions data and should not be used for regulatory reporting or a lifecycle comparison. An electric tariff does not identify the physical source of every kWh. We do not calculate petrol-versus-EV emissions by treating litres of petrol as kWh of grid electricity.

Updates and corrections

Sources on this page were checked on 7 September 2026. EIA, Ofgem and Eurostat have different publication schedules and observation periods. The GB reference expires after 30 September; check the relevant source before calling any figure current. Routine website builds do not advance this review date.

Our calculation methodology explains how examples and presets are chosen. If you report a tariff correction, include the supplier or regulator URL, effective dates, customer category and whether tax or fixed charges are included.

Calculate it yourself

Imported source date: 2026-09-07. Review details have not been independently verified.