Heating System Fuelled by Red Diesel

There was a discussion on different heating systems a few months ago, but I cannot find it - also I don't re-call any comment on the above.  But just had a discussion with a local British run heating contractor who have a good reputation and they surprised me by suggesting that we install a boiler and radiators etc powered by red diesel.

I know there's a big hoo-haa in UK with red diesel being illegally used in taxis etc as the cost is 25% or so of the fully taxed fuel.   I'm told it's totally legal to use for domestic purposes and massively cheaper than diesel sold at garages, but is it an area that might change - will the Spanish government be looking to increase tax to fill their empty coffers shortly ?

Most grateful for any advice on the subject - is it commonplace in Spain.

Yes it is common to use gas oil in central heating sytems here as in UK.

We filled up in December and paid 91 cents per litre so more expensive than UK.  The price  tracks normal diese prices.

It is of course also illegal to use in vehicles here in Spain.

Jean