Electricity charges

It's not the unit rate that is the big cost of an electricity supply it is the standing charge.

My 3.3 kw supply costs me about 15 euro per month with no usage.

A 5 kw supply with no usage will be around 30 euro per month with no usage.

Different suppliers have different tariffs, so it's worth checking them out first. And, as Roland has said, the equivalent of standing charges (shown on your bill as 'potencia') makes up around 50% of the bill and you pay a rate based on the potencia that you have / need. 

You say "additional heating" but it's not clear what heating your property already has? 

Electricity is generally less economical for heating (due to the higher cost per kWh) than gas, but many properties in Spain are electric-only (and they need less heating due to warmer weather than the UK). Portable gas heaters are popular for occasional usage and many properties have wood-burners or fireplaces. Also, many modern air-con systems have the functionality to provide heating (but are pricey to run for extended periods).

Your link to statista was incomplete btw.

Thank you very much for all the details. To be honest, the house we are moving into, has no heating at all. As we are currently living in cold Germany, we assumed that there is probably no need for much heating in winter as it is rarely goes down below 10 Degrees. Is it the case? What do the actual winter temperatures feel like, considering it is high humidity and our house is just 50 m from the Mediterranean beach (facing North)? 

The site below has really useful historic data, which shows that it gets cold in November to March and I certainly wouldn't want to be living in a house with no heating in those periods.

https://www.meteoblue.com/en/weather/historyclimate/climatemodelled/la-manga-del-mar-menor_spain_6355177

We live in Scotland (so we're used to the cold!), but we are moving permanently to our villa in literally two weeks. 

Our property is inland and at 710m altitude, so not a fair comparison, but when it's cold we feel cold. It's the property in the picture on my profile. We have two wood burners and use one. We have a fireplace but don't use it. The property has electric radiators installed and we have used them occasionally to take the chill off our bedroom. We had air-con installed, which also has the functionality to provide heating, but we haven't used this yet as we weren't there last winter.

You say 'house' - you should consider the differences between detached houses and terraced houses as far as heat loss and heat shared with/by neighbours. Most houses in this area of Spain are built with little or no insulation and limited opportunity to add any without expensive works. Are the rooms large or small?  Large or small windows? You are facing north so won't get much heat from the sun through windows. Is it an old house? It would be unusual not to have some sort of heating or a fireplace?

Portable gas heaters (with butane gas bottle) are probably the easiest initial option as they deliver heat much more quickly than electric radiators, you just need to ensure adequate ventilation and also avoid condensation issues. I would suggest trying these and see how you go...

Hope this helps!

Congratulations on moving to Spain, we are looking forward to our move soon too. Many thanks for the useful tips and a website, it certainly gives us a better picture what to expect:-)