I've been asked many times recently
The answer is somewhat complex, and depends on the individual circumstances. At the moment heating oil is priced at around €900 per 1000 litres. Most households require between 1500 and 2000 litres a year.
There are 9.821 Kw/hours of heat in a litre of kerosene.- that gives a gross heat output costing 10 cent per Kw/h. Allow for boiler efficiency and for system losses, and I would guess that a figure of between 11.50 and 12.50 cent per Kw/h of delivered heat would be a reasonable estimation.
Electricity is 100% efficient as a heating fuel. It can also be very carefully controlled and directed to where you need the heat without heating half the house and all the piping and the boiler itself.
Currently the standard electricity charge is 0.1619 per Kw/h but most suppliers offer discounts so you should not be paying more than about 14.50cent per Kilowatt hour.
If you have a poorly adjusted, old, or inefficient oil heating system, and with the current price of oil, you would do as well or maybe even better with electricity.
Coal has now become the only viable option, certainly for poorer families. There is a massive trend towards solid fuel heating. New high efficiency multi-fuel stoves and boilers can offer up to 90% efficiency or in other words, as good as most oil heating systems.
Smokeless coal can be bought for 35 cent per Kg. Petroleum coke smokeless mixes are very efficient coals, and you could expect to get 7 kilowatts for an hour per kilogram. Allow for an overall efficiency of say 75% on average, and the cost per Kilowatt is only 6.7 cents per kilowatt hour. That is nearly half the current cost of oil heating.
I personally have 100% heated my house the last season with coal and saved hundreds of Euro. You do pay a price for using coal though, coal takes a certain amount of tending and work, and is dirty.
But if you need heat and also need to save a lot of money, and you are willing to put some effort into it, solid-fuel is the way to go at the moment - that is until the Irish Minister for Hardship goes and taxes us some more. But then we will find some other ways around it!!