Electricity Cost Calculator Ireland

Checking energy costs after Budget 2027? Our winter electricity-bill guide explains the absence of a new energy credit, seasonal bill assumptions and ways to compare solar payback. Use the calculator here to estimate one appliance or load at a time; it is not a complete supplier bill comparison.

What this calculator is for

This calculator estimates the incremental running cost of an appliance from its power, usage pattern and electricity unit rate. It is useful for understanding what heaters, immersions, dehumidifiers, dryers, EV-related equipment and other loads can add to a bill.

For solar planning, use the Compound Solar Hub to connect appliance demand to solar quotes, grant rules and payback. Compare two import and export offers with the Solar Export Rate Comparator.

For whole-house tariff selection, use our Electricity Tariffs in Ireland guide to compare 24-hour, day/night, smart, EV and dynamic pricing before entering the relevant unit rate here.

How to read the result

The calculator focuses on usage charges, not the household’s fixed standing charge. Reducing appliance kWh lowers the variable part of the bill, while a standing charge generally remains whether this individual appliance is used or not. On time-of-use plans, when the appliance runs can matter as much as how many kWh it uses.

Worked example

Using 4,200 kWh a year at €0.30/kWh gives €1,260 in energy charges before standing charges, VAT, levies and any time-of-use differences. Moving some usage to a cheaper night rate can reduce cost without reducing total kWh.

Irish context

Irish bills can include unit charges, standing charges, VAT and the PSO levy. Smart-meter tariffs can vary by time of day, and from June 2026 dynamic tariffs can vary every half-hour. CRU advises customers to compare tariffs using their actual consumption pattern where possible.

What can change the answer

Annual consumption, day/night split, smart tariff windows, supplier discounts, standing charge and price changes all matter. Electric heating, heat pumps and EV charging can materially change a household’s load profile.

Common mistakes to avoid

Do not compare suppliers using the unit rate alone. A lower unit rate can be offset by a higher standing charge or discount conditions. Do not assume the advertised rate applies all day on a smart tariff. And use actual kWh from bills rather than guessing where possible.

Related Compound tools

Use the EV Charging Cost Calculator for vehicle charging, Solar PV Payback Calculator for generation and the Solar + EV + Battery Optimiser for time-shifting scenarios.

Frequently asked questions

What is a kWh?

One kilowatt-hour is the energy used by a 1 kW appliance running for one hour.

Does the calculator include standing charges?

Where entered, yes.

Do smart tariffs always save money?

No. Savings depend on when you use electricity.

Are dynamic tariffs the same as day/night tariffs?

No. Dynamic prices can change every half-hour.

Use your own load profile where possible

Annual kWh is the starting point, but two households using the same 4,000 kWh can face different bills if one consumes heavily at expensive peak times and the other shifts flexible loads overnight.

Smart-meter data can reveal that pattern. Large flexible uses such as EV charging, immersion heating, dishwashers, laundry and batteries can sometimes be moved without reducing comfort.

When comparing tariffs, calculate at least three elements separately:

• the annual standing charge;
• the weighted cost of the kWh you expect to use in each time band;
• any conditions attached to discounts or introductory offers.

A tariff with a very cheap night window can be excellent for an EV household but poor for a home with most consumption during the evening peak.

Also remember that electricity prices can change during the contract period. This calculator is most useful as a snapshot using today’s tariff and your recent annual consumption, then repeated when a fixed discount or contract period ends.

Advanced mode: cycling loads and off-peak use

A nameplate wattage is a maximum or rated input, not always a continuous draw. Thermostatically controlled appliances can cycle on and off, while variable-speed equipment can spend long periods below rated power. Advanced mode therefore lets you apply a duty-cycle percentage to the hours switched on.

You can also allocate a percentage of this appliance’s kWh to an off-peak rate. Compound calculates a weighted unit rate from the main and off-peak tariffs and applies it to the modelled energy use.

For a device that actually draws 2 kW continuously, one hour uses 2 kWh. If a 2 kW appliance is switched on for one hour but averages a 50% duty cycle, the model uses 1 kWh. A plug-in energy monitor or manufacturer telemetry is preferable to guessing where available.

Standing charges are deliberately excluded

This tool answers “what does running this appliance add?” rather than “what is my full electricity bill?”. A household standing charge is normally payable regardless of whether one particular appliance runs, so allocating the whole fixed charge to that device would overstate its incremental cost.

For whole-tariff comparisons, evaluate standing charges, discounts, VAT, levies and your complete time-of-use consumption profile separately.

Appliance cost is a marginal-cost question

This calculator is designed to answer: what extra electricity cost is caused by running this load?

That is different from asking for the full household electricity bill. Standing charges and some levies are payable regardless of whether one appliance runs for an extra hour, so assigning the entire fixed bill to a television, heater or server would exaggerate its incremental cost.

For an appliance decision, the key inputs are power, operating time, duty cycle and the unit rate that applies when the load actually runs.

Duty cycle matters for thermostatic and cycling loads

A 2 kW appliance does not necessarily consume 2 kWh every hour it is switched on. Heaters, fridges, pumps and other thermostatic devices often cycle.

Advanced mode therefore allows a duty-cycle assumption. A 2 kW heater operating at a 50% average duty cycle over four hours is modelled differently from a device drawing 2 kW continuously for the same period.

Where possible, use a plug-in energy monitor or a smart-meter reading to replace assumptions with measured consumption.

Time-of-use tariffs can change the answer

On a flat tariff, timing does not matter to the unit cost. On a smart or day/night tariff, it can matter a great deal.

For flexible loads such as immersion heating, EV charging, dishwashers or some heat-pump operation, compare the same kWh at the day and off-peak rates. The energy requirement may be unchanged while the cash cost moves because the load is shifted in time.

The EV Charging Cost Calculator is better for vehicle-specific charging, while the Solar + EV + Battery Optimiser is designed for households coordinating multiple energy flows.

Annualise carefully

A small daily load can become meaningful over a year. Conversely, a high-power device used for only a few minutes may cost less than expected.

When annualising, use realistic operating days rather than automatically multiplying every result by 365. Seasonal heaters, dehumidifiers, pumps and garden equipment often have very different use profiles across the year.

Whole-home tariff comparisons need more inputs

If you are comparing electricity suppliers, this calculator is only one part of the decision. A full tariff comparison should include the complete annual consumption profile, day/night or half-hourly usage where relevant, standing charges, discounts, VAT, levies and any conditions attached to the tariff.

CRU guidance on electricity bills and dynamic tariffs is the appropriate reference point for those broader comparisons.

Method and limitations

The tool converts watts to kW, applies the entered operating hours and days, and in Advanced mode applies the duty cycle and weighted main/off-peak unit rate. It does not reproduce every supplier discount, levy, VAT treatment, standing charge or half-hourly dynamic tariff.

Useful sources

• CRU — Your electricity bill
• CRU — Dynamic price tariffs