Energy storage - when is it worth it?
Are you thinking about energy storage for your photovoltaic installation? You're not alone. More and more homeowners are realizing that photovoltaics alone is just the beginning of the path to energy independence. The times when surpluses were handed over to the network at a favorable conversion rate are over. Today, in the era of net-billing, every kilowatt-hour of energy produced matters. Let's take a look at when an energy storage is a sensible investment and how to choose its size to suit your needs.
What does energy storage really give you?
Imagine a typical day: the sun shines brightest at noon, when most of the household is at work or school. Your photovoltaic system then produces the most energy, but there is no one to use it. In the evening, when everyone returns home and turns on the appliances - from the kettle to the washing machine - the sun is already setting. As a result, you have to buy energy from the grid at higher prices, even though you have produced a surplus of it during the day.
The energy storage solves this problem by acting as a great powerbank for your home. It accumulates excess energy during the day to put it at your disposal in the evening and at night. This is not only a matter of savings - it is also energy security and comfort.
Net-billing system and warehouse profitability
In the current net-billing system, for every kilowatt-hour spent on the grid, you receive funds according to the monthly average price of energy on the market. The problem is that when you need to buy this energy later - you pay much more, because distribution fees and other components of the bill come to the price of energy. In practice, this means that for 1 kWh given to the grid, you can buy later only about 0.6-0.7 kWh. The energy store allows you to keep the produced energy for yourself and use it in full.
What size warehouse to choose?
Choosing the size of a warehouse is the art of finding the golden mean between your needs and costs. Too small will not fulfill its role, too large will be an inefficient investment. Here is a proven method:
1. First, check your daily energy consumption in the evening and at night (usually from 16:00 to 8:00 the next day). It's energy that you could draw from the storage instead of the grid.
2. Next, analyze how much energy your PV system produces above the current consumption in solar hours. This is a surplus that you can store.
For an average single-family house with a 10 kWp installation, the optimal warehouse has a capacity of 10-15 kWh. Such a size allows you to accumulate surpluses from a typical sunny day and meet most of the evening and night needs.
High or low voltage - what to choose?
There are two main types of energy storage on the market:
High voltage storage (e.g. SolarEdge, Sofar) - a traditional solution where one controller manages the entire battery bank. The advantage of Chinese systems (such as Sofar) is a lower price. The advantage of the SolarEdge system is an advanced power optimization system that generates more energy on roofs with more shade or more complex ones. The SolarEdge system is usually around 40-60% more expensive than Chinese solutions. When expanding a high-voltage system, it is often necessary to replace the controller with a larger one.
Low-voltage storages (for example, Breeze) - each module has its own controller, which makes it possible to easily expand the system in the future. They are also safer in operation, which is important when the warehouse is installed in a garage or utility room. Low-voltage systems are usually more expensive, but also the Polish Breeze system has a price similar to Chinese high-voltage warehouses - the difference in price can be up to 5%.
When will the energy store pay off?
Let's take an example: a house with a 10 kWp installation and a 10 kWh storage. Typical savings are:
· Increase in autoconsumption from 20-30% to 60-70%
· Reducing the amount of energy purchased from the grid by about 3000-4000 kWh per year
· At current energy prices, this means savings of the order of PLN 3000-4000 per year
With a warehouse cost of about PLN 25-35 thousand (with installation) and a subsidy from the My Power program (up to PLN 16 thousand), the real payback period is 4-6 years.
Energy storage is not just about savings
However, remember that energy storage is not just a financial issue. It is also:
· Power outage protection
· Protection of equipment against voltage surges
· Ability to charge the electric car with its own energy
· Greater independence from changes in energy prices
Added to this is the ecological aspect - the more energy you consume directly from your own installation, the less transmission losses and the smaller the carbon footprint.
Recent research shows that the average home in 2030 will consume up to 3 times more electricity than it does today. The main reason is the growing popularity of electric cars and heat pumps. That is why it is so important that the energy storage system is ready for expansion.
Modern hybrid systems use advanced machine learning algorithms to predict energy consumption. By analyzing your habits for several weeks, the system can predict with 90% accuracy how much energy you will need at a specific time of the next day.
If all single-family houses in Poland were equipped with photovoltaic systems with 15 kWh energy storage, the total energy storage capacity would be greater than all pump-top power plants in the country. Such a distributed storage system could revolutionize the Polish energy industry.
In conclusion: if you already have a photovoltaic installation or are planning to install it, energy storage is a natural next step towards energy independence. With current energy prices and subsidies available, it's an investment that not only pays off but also provides energy security for your home.
