Electric boiler running cost calculator
Enter your electric boiler’s input rating, hours per day and tariff. The estimate uses the same power × time × rate method as the electric heating calculator.
Prepared from existing project material on 24 October 2026. Editorial review: not yet recorded. Live figures use the current record; existing evidence dates are unchanged.
See also: Electric heating cost calculator · Economy 7 calculator · Heat pump running cost calculator
Enter your boiler’s input rating, hours and tariff. Hours must be 0–24, days 1–31, on-time above 0 and no more than 100%, with a positive power and tariff.
Estimate only. No assumed boiler rating, installation cost or standing charge is added.
What this electric boiler calculator estimates
This is a running-cost calculation for a resistance electric boiler. It estimates the electricity used when an element draws the input power you enter, for the hours and thermostat on-time you specify. It does not size a boiler, recommend an electrical supply or estimate the cost of installing one. Those decisions require an assessment of the property, heating system and manufacturer’s requirements.
The fields are labelled in kilowatts, hours per day and pence per kWh. Start with the boiler’s actual electrical input rating, not the heat output of a gas boiler you are replacing. No supposedly typical electric boiler size has been invented as a default. The rate may fill from the current reference record, but you can replace it with your own tariff before using the result.
Find the input power and operating hours
Check the boiler’s data plate, manual or installer’s paperwork for its electrical input. Some models have staged elements or limit their draw depending on demand. If your paperwork lists more than one power, ask the manufacturer or installer which setting applies. Do not assume that a domestic plug-in heater’s rating describes a whole-home electric boiler.
Hours per day should describe the period you are modelling. A programmed heating period is not necessarily continuous full-power operation. The thermostat on-time field lets you account for cycling where you have a reliable measurement or known operating pattern. If you do not, use full power as an explicit scenario and compare it with meter readings rather than presenting it as actual consumption.
How the cost is calculated
Multiply the electrical input in kW by hours and the share of that time the element runs. That gives kWh per day. Multiply kWh by the electricity unit rate, dividing pence by one hundred to obtain pounds. The monthly result repeats that daily pattern for the number of days entered; it is not an annual weather model.
The calculation follows the existing electric-heating calculator method so the same inputs produce the same energy cost. It deliberately excludes installation, servicing and a new standing charge. A standing charge already paid for the electricity supply is not charged again for each appliance. If removing a gas connection is part of your plan, compare the full household tariff and supply costs separately rather than assuming they disappear automatically.
Hot water and space heating are different loads
An electric boiler can serve space heating and, depending on the system, hot water. The demand depends on heat loss, desired temperature, cylinder arrangement and household use. A brief hot-water heating period is not interchangeable with a full day of space heating. Where possible, model the loads separately with their actual input and run time, then compare their combined consumption with your meter.
The tool does not infer heating demand from bedrooms or floor area. It also does not assume that the boiler operates at its nameplate rating continuously. A qualified installer should check system design and the electrical connection. Do not change protective equipment, wiring or boiler settings beyond the manufacturer’s user instructions to make a calculator result look cheaper.
Compare your tariff before relying on off-peak heat
If you have a single-rate tariff, use that rate for every hour in the scenario. If you have Economy 7 or another time-of-use arrangement, calculate each period with its own rate and the energy actually used then. Applying a cheap night rate to the whole day would understate the bill. The existing Economy 7 calculator can compare the resulting day and night totals.
Heat must be available when your home needs it. A system with thermal storage may shift some demand, but this tool does not invent the size, losses or available storage of your cylinder. Confirm exact off-peak times with the supplier and meter arrangement. Do not substitute a current EV rate into an Economy 7 calculation or assume eligibility for a smart tariff without checking its terms.
Compare electric boilers with other heating options
A heat pump uses a different process and can deliver more heat than the electrical energy it consumes. This resistance-boiler calculation must not be used by entering a heat pump’s advertised heat output as electrical input. Use the dedicated heat pump running-cost calculator and its efficiency assumptions to compare options on a consistent heating demand.
For an existing gas boiler, the gas-boiler calculator accounts for the efficiency assumptions used in that model. Compare equal useful heat, actual tariff rates and the work needed to change the system. A low installation price does not establish low running costs. Ask for itemised written quotations and clear assumptions before making a replacement decision. No finance recommendation or guaranteed payback is made here.
Check the estimate against your home
Try a realistic winter day and a milder day separately rather than stretching a cold-weather schedule across the whole year. Keep a note of input power, hours and the tariff period used. If your meter shows much less consumption, investigate cycling and other loads rather than assuming either the boiler or the calculator is necessarily faulty.
The next useful step is to open the general electric heating calculator if you want to compare room heaters on the same method, or use the heat pump tool for a different technology. Your supplier can confirm tariff rates, while the installer can confirm the boiler’s technical settings. An estimate is a planning aid, not a bill, installation design or assurance that the chosen system suits your property.