I am "All Electric" and yes, it's running cost will be higher than that of a Gas Fired Heating System,
However, you will not have to install a Boiler, which needs Servicing every year, miles of piping and radiators and all the redecoration work that that entails. The whole could set you back many thousands of pounds.
I pay less than £100 a month to run my Flat but, of course, were I to increase the background heating, it could cost more.
I do not lose room space to Radiators and my Water Heating Boiler is out of the way in the loft. I would reckon that the extra cost is about 20% per annum, which would take 16+ years to amortise the Cost of Installation of a Gas System and that does not take into account, Boiler Maintenance and Replacement