Solar panels and battery

In March 2022, I installed 12 solar panels, 450 W each one, spreading them across the roof of the house from east to west, following the daily route of the sun.

Until the end of 2022, I’d been analyzing the performance of the solar system, at the same time redistributing and adjusting the sources of consumption in my house according to the time of day and electricity prices.

For better understanding here comes the raw data about my house:

Region: Spain.
Family of 4 people.
Electric heating (heating pump air — water — max. 15 kwt) underfloor heating + split systems (if necessary)
The area of 400 square meters is divided into three heating/cooling zones.
Air conditioners — 4 pcs. Powerful
Swimming pool (cleaning, a very voracious mechanism).
Sauna 7 kwt (in winter, is used once a week) — approximately 40 kwt at a time.

Here is the data for the year 2022 (incomplete) of solar panels' operation without a storage battery.

Early in summer 2022, it became obvious that every sunny day I return a large amount of energy to the electricity supplier’s grid, because I can’t consume it all, and after the sunset, I start buying electricity from this company, just at the most expensive hours (evening and morning).

There are three tariffs in my region (these are not current prices, they are mentioned only for comparison)

Morning/evening — Red 0,30 €
Day — Yellow 0,25 €
Night + weekends — Green 0,13 €.
Payment from the electricity company to me for sharing excess energy — 0.11 €

I installed the Sonnen 10 kwt storage battery at the end of 2022 and now I’m presenting the data of the system’s performance for the full year 2023 with real prices.

Let’s make it clear.
My solar system produced about 8,000 kwt (8MWt).
The house has used (consumed) 10 000 kwt
Let’s take the average cost of energy from my electricity company for the year 2023 — 0,25 € / kwt.
That means that I have saved (earned) — 2000 € for the year 2023. It is worth considering that the cost of electricity has fallen by 50−70%(!!!) compared to 2022.

Economics.

The cost of my solar system:
Panels (12), control module, installation, license (!) — 10 000 €
Sonnen 10 kwt battery, installation, license — 10 000 €

What is the license for?

According to Spanish laws, you can install solar systems (and batteries) only if the manufacturers are certified in Spain. If someone decides to save money and install some cheap Chinese panels, then, first of all, not a single electricity company will sign a contract with him or her, and therefore will not pay for excess energy exported to the grid. Secondly, and this is the key issue, he or she is not entitled to compensation for the cost of equipment from the European Union, which is up to 50% of the total cost, including installation.
I’ve done some rough math…

The cost of my system is 20 000 € - 50% = 10 000 €.

Earned (not paid to the company):
2022 — 2100 €
2023 — 2000 €

If the price of electricity stays at today’s level, does that mean that my solar system will be fully paid off in three years? WOW!!!

By the way, the warranty for all the equipment is 10 years, so I’m not too worried if something is broken. And it requires almost no maintenance service.

In real life, according to the invoices it looks like this:

In January, February, November and December I pay about 100 € to the electricity company.
The rest of the 8 months — 0 €

And in the conclusion some FAQ.

Does it make sense to buy a storage battery? Is it too expensive and won’t pay off?

It’s obviously up to you to decide! My reasoning is as follows:
If the city grid goes down (failure, hurricane, etc), my house will be autonomous for up to 2 days with the minimum necessary consumption.
The battery charges during the day (for free), gives up power in the evening and in the morning when the price is at its highest point.
I can manage the battery settings through the app. There are a lot of settings out there.
If you have an electric car, battery management is a must.

How do I set the optimal electricity consumption?

My large and very energy intensive house consumes an average of 40 kwt per day. This is almost incredible, according to my friends. Let me tell you how I adjusted the consumption.

1. All lighting is definitely replaced with LEDs, and it’s on when needed only. I installed movement sensors, light sensors (outside), etc.
   The biggest energy eaters are: heating, swimming pool, air conditioners, sauna.
2. I turn on the sauna on Saturdays (price 0,12 €/kwt) for 6 hours — 0,72×4 = 2,88 € per month (only in winter).
3. The heating is divided into two zones: Bedrooms and a Living room. They are controlled by smart thermostats, which are programmed as follows: the living room heating is switched on at night until 6 am at the cheapest time (if there is no energy left in the battery). The bedrooms are heated from 6pm to 12am, at this time the battery is almost always fully charged and gives up that energy.
4. The pool in winter runs for 2−3 hours at night only. In summer, it runs during the day, 6 hours total.
5. Air conditioners run only in summer, as needed, during daylight hours or from the battery in the evening, they do not run from the city grid.
6. The washing machine, dryer and dishwashers in winter run at night, in summer during the day.

Almost all the technologies used in my house I have integrated into the Smart Home System, although it is not obligatory. Evidently, depending on the season, I reconfigure sensors and thermostats but all the programs are already created and tested, and I just need to press a button on my phone «Spring» «Autumn» etc.

I spend a lot of time traveling but still I have to manage other properties being hundreds of miles away, so everything is integrated into one program with remote access and I can adjust any configurations from anywhere in the world. But this is probably a topic for my next article.