Electricity Bill, kWh & Solar Calculators

List every appliance with its wattage and daily hours, convert each to kWh per month (watts ÷ 1000 × hours × days), add them up, multiply by your tariff and add any fixed standing charge. This calculator does all of that and ranks the results for you.

The three usual causes are underestimated runtime, forgotten always-on devices, and tiered tariffs where later units cost more than the first ones. Compare your estimate with your meter reading over a week and adjust the hours until they match.

A fixed daily fee that covers grid connection and metering, applied whether you use any electricity or not. It is not affected by efficiency measures, so keep it separate from your per-unit costs when you evaluate savings.

It varies hugely by climate and home size: roughly 250–400 kWh a month for a small apartment without electric heating, 600–900 kWh for a family home with electric heating or heavy air conditioning, and more where there is a pool or an EV.

Yes. Add every appliance and set realistic hours. For a small business, remember to include lighting across full opening hours, refrigeration around the clock and any equipment left on standby overnight.

Multiply watts by hours and divide by 1,000. A 500 W appliance running 4 hours uses 500 × 4 ÷ 1000 = 2 kWh. To go the other way, multiply kWh by 1,000 and divide by hours to get average watts.

One unit is one kilowatt-hour: 1,000 watts drawn for one hour. It is the quantity your meter counts and your bill prices, and it is identical in every country even though the price varies enormously.

Indicative 2026 averages: about $0.17 in the US, £0.247 in the UK, ₹8 in India, A$0.33 in Australia, €0.285 in the eurozone and R2.90 in South Africa. Always check your own bill, since regional and tariff differences are large.

Find the wattage on the rating plate, estimate the hours it actually runs, then use the formulas above. For fridges and washing machines, prefer the annual kWh figure on the energy label because it already accounts for cycling.

Only as a route to watts. Watts = volts × amps, so a 5 A appliance on 230 V draws about 1,150 W, and on 120 V about 600 W. Convert to watts first, then use this calculator.

Check the rating plate on the back or underside, the manual, or the energy label. If the label shows amps instead, multiply amps by your voltage (230 V or 120 V) to get watts. The most reliable method is a plug-in energy meter, which measures actual draw rather than the maximum rating.

Typically air conditioning or space heating, then water heating, then the tumble dryer, oven and refrigerator. Together those five usually account for the majority of a household bill, which is why they each have a dedicated calculator on this site.

Annual kWh is multiplied by your region's grid emission factor in kg CO₂ per kWh. Grids vary enormously — Canada is around 0.12 kg/kWh thanks to hydro and nuclear, while South Africa is near 0.93 kg/kWh because of coal. The same appliance therefore has a very different footprint depending on where it is plugged in.

It is the fraction of time an appliance actually draws its rated power. Set it to 100% for a bulb or TV. Set it to 40–60% for an oven, air conditioner or fridge, whose thermostats cycle the load on and off.

They are as accurate as your inputs. The arithmetic is exact; the uncertainty is in wattage and runtime estimates. Measure your wattage with a plug meter and use your real tariff and the result will typically be within a few percent of your bill.

Typically 7 to 14 years depending on install cost, tariff, sun hours and how much you self-consume. High electricity prices and high self-consumption shorten it dramatically; heavy export lengthens it.

Roughly 4,000 kWh a year in the UK, 6,500 in southern Europe or Australia, and up to 8,000 in the Gulf. The calculator above uses your own sun hours and performance ratio rather than a generic figure.

Use it, almost always. Feed-in tariffs are commonly a quarter to a fifth of the import rate, so a unit consumed on site is worth four to five times a unit exported.

0.78 to 0.84 for a well-installed system. Below 0.75 suggests shading, soiling, an undersized inverter or a poor install. Above 0.85 is unusual outside ideal conditions.

Yes, at reduced output — typically 10 to 25% of clear-sky generation. Peak sun hours figures already average this in across the year, which is why they are lower than daylight hours.

A battery raises self-consumption from around 40% to 70–80%, which increases annual savings, but it adds substantial upfront cost and has its own lifespan. In most markets it lengthens payback rather than shortening it, and is better justified by outage resilience than by economics.

Replacing a single 60 W incandescent with a 9 W LED running 5 hours a day saves about 93 kWh a year, worth roughly $16 in the US or £23 in the UK. Across a dozen bulbs that is commonly $150–$280 a year, for an outlay of well under $50.

For frequently used fixtures it is typically 2–6 months. Bulbs used only a few minutes a day take much longer, which is why it makes sense to prioritise high-usage rooms and leave the rest to fail naturally.

Quality LEDs are rated for 15,000–25,000 hours, against roughly 1,000 hours for an incandescent and 8,000–10,000 for a CFL. At 5 hours a day, a 20,000-hour LED lasts around 11 years, so replacement cost savings add to the energy savings.

The energy saving is smaller — perhaps 14 W down to 9 W — so payback is slower, typically 1–3 years. It is usually best to replace CFLs as they fail, unless you want instant-on brightness or dimmability, which LEDs do far better.

A trace amount in some smart or illuminated-switch installations, typically well under 0.5 W. It is not usually worth worrying about, though a whole house of smart bulbs idling at 0.4 W each can add a few kWh a year.

Around 64% in practice. A fluorescent fitting draws about 50 W including ballast losses while an equivalent LED panel draws 18 W, saving roughly 90 units a year at 10 hours a day.

Usually under a year, and often under six months in areas with long running hours. At 10 hours a day, a ₹350 price difference is repaid in about five to six months.

Yes. A magnetic ballast consumes 10 to 14 W of its own, which is why a '36 W' tube draws close to 50 W at the meter. Electronic ballasts are better but still add a few watts.

Only if you also bypass or remove the ballast. Otherwise you keep paying the ballast loss. A retrofit tube in a properly rewired fitting performs almost identically to a panel.

Typically 25,000 to 50,000 hours against 8,000 to 15,000 for a fluorescent tube. At 10 hours a day that is roughly 7 to 14 years, so you also save on replacements and labour.