EuroWattCalc
Interactive planner

Whole-home energy budget calculator

Build a simple monthly electricity budget from the appliances you actually use, then spot the largest cost driver.

Reviewed 2 September 2026Calculations run locally in your browser
Your tariff

Monthly energy plan

Monthly energy—kWh
Monthly cost—usage estimate
Annual equivalent—same usage × 12
Largest cost driver——

This planner estimates variable electricity usage only. Fixed charges, taxes and tariff structures can sit outside the result.

How the planner calculates each appliance

For every row, the planner converts watts to kilowatts, multiplies by hours per day and days per month, then applies the electricity price you enter.

Monthly kWh: watts ÷ 1,000 × hours/day × days/month
Monthly cost: monthly kWh × price per kWh

Use it as a prioritisation tool

The “largest cost driver” is not automatically the appliance you should replace. It is simply the row contributing the highest estimated variable electricity cost under your inputs. A high-power device used rarely may cost less than a lower-power device that runs every day.

Where estimates can diverge from a bill

  • Thermostatic and variable-speed devices do not always draw their rated power continuously — a fridge or heat pump modulates output once it reaches its target temperature.
  • Some appliances are better modelled from measured kWh per cycle than from maximum watts, particularly washing machines, dishwashers and tumble dryers.
  • Time-of-use tariffs require separate peak and off-peak modelling rather than one blended price.
  • Appliances left out of the list — even small always-on devices like routers or set-top boxes — are not included in the total.

A practical way to build the list

Rather than guessing every appliance in the home, start from your last bill's total kWh and work backwards: add the handful of appliances you believe use the most, check whether the planner's total is in the right range, then adjust hours and days until it roughly matches. This "reconcile to the bill" approach is usually faster and more accurate than trying to itemise everything from scratch.

What counts as one appliance vs several rows

Group near-identical devices into one row with a combined wattage rather than adding each separately — for example, "living room lighting" as one row at the combined wattage of all bulbs, rather than six separate 10 W rows. This keeps the list readable without losing accuracy, since the underlying arithmetic is the same either way.

For time-varying prices, use the time-of-use shift calculator. For one-device calculations, use the electricity cost calculator. Once you know which appliance drives the most cost, test whether replacing it is worthwhile with the upgrade payback calculator.

Frequently asked questions

How many appliances should I add?

Start with the handful that run daily or for long periods — fridge, washing machine, oven, entertainment devices, heating or cooling. Small, occasional-use items rarely change the picture enough to matter, and adding every appliance in the home makes the list harder to read without improving accuracy much.

What if I don't know an appliance's wattage?

Check the rating label on the appliance itself, the manual, or the manufacturer's website — most list a rated wattage or amperage (multiply amps by your mains voltage for watts). A plug-in energy meter gives the most accurate figure for anything that cycles on and off.

Why does the 'largest cost driver' change when I edit hours?

The largest driver is recalculated from your current inputs every time you change a value, since it depends on both power and how long each appliance actually runs, not on power alone. A high-wattage appliance used briefly can rank below a modest one that runs most of the day.

Does this planner replace my actual electricity bill?

No. It estimates the variable, usage-based part of your bill from the appliances you list. Standing charges, taxes, network fees and any appliances you have not added are outside the estimate, so the total will not match your bill exactly.

Can I use this for a whole year instead of a month?

The planner works in monthly figures and also shows an annual equivalent, calculated as twelve times the monthly estimate. If your usage varies strongly by season — heating in winter, cooling in summer — build a separate monthly budget for a representative month in each season instead of relying on one estimate.

What does 'Copy summary' do?

It copies a plain-text breakdown of every appliance row, the total monthly kWh and cost, and the annual equivalent to your clipboard, so you can paste it into a note, spreadsheet or message without retyping the numbers.