Can you sell electricity back to the grid in Spain?

I have been doing a little research because the question has come up especially for one of our clients for whom we are designing a Passive House in Sotogrande. Actually the question we are facing is do we need batteries or can we use the grid as a giant battery and this question “Can you sell electricity back to the grid in Spain?” came up as part of that and I wanted to share what I know.

Until recently it was not possible to sell electricity back to the grid (in fact as I write 8th October 2019 it is not possible). In fact for people who were generating their own electricity (over 10kw) there was an additional charge to cover the maintenance of the grid popularly known and derided as the sun tax. I believe the law changed on 5th April 2019.

I have been told that this month, October 2019, all the power companies are supposed to offer their customers the possibility of buying the electricity that their customers produce. The price they pay you will be around 6 cents per Kwh while the price you pay them around will be around 18 cents per Kwh. They will not pay you in cash but only discount against what you consume with a balancing account each month.

So if in a month you produce 500kwh then your account is credited with 500 x 0.06 = 30€. If you draw from the grid 100kwh your account is debited 100 x 0.18 = 18€. But they don’t pay you 30-18=12€ which they should. I believe you just donate the difference. And they do still charge you the fixed standing charges.

Aura seems to be a supplier that are saying you can now sell your excess energy back to the grid. I called them and they said its live now and legal.
https://www.aura-energia.com/preguntas-frecuentes/

When we spoke they said they are still deciding on what prices to pay.

Then they sent me an email saying that the “procedures” are not yet formalised without explaining what these might be.

If I ask myself why there isn’t a clear statement from Aura I can only imagine it is because there is still a lot of uncertainty about what might happen.

It seems likely at the moment that you will be able to use the grid as a giant battery and not have batteries yourself but that you won’t be able to make money by selling excess electricity to then grid.
We need to see how the situation develops over the forthcoming months and evaluate the situation taking into the account the cost of the batteries and other pros and cons of a battery system.

Batteries do not take up much space and we need a mechanical installations room anyway in the basement. So if we do go for batteries there is space for them. We are still in the early stages of the design so we don’t have to make a decision yet.