Autoconsumption in photovoltaics - what is it and what does it depend on?

Autoconsumption in photovoltaics is a term that refers to the consumption of electricity produced by a photovoltaic system on site, i.e. directly by a household, business or other entity that has a photovoltaic installation. Autoconsumption refers to the use of electricity produced by photovoltaic panels to power equipment and systems at the same location where the electricity is produced.

What does the level of self-consumption depend on?

The level of self-consumption depends on several factors:

  1. Energy consumption profile: If energy demand coincides with periods of peak production (usually during the day when there is the most sunshine), the level of autoconsumption will be higher.
  2. Size of photovoltaic installation: A larger installation can produce more energy than is consumed on site, reducing the percentage of self-consumption.
  3. Energy storage system: Batteries allow surplus energy to be stored and used at times when production is lower than demand, increasing self-consumption.
  4. Intelligent energy management: Energy management systems (EMS) can optimise energy consumption, for example by automatically switching on equipment during peak production periods.
  5. Building characteristics and equipment: Buildings with energy-intensive equipment and systems (e.g. air conditioning, electric heating) can make better use of the energy they produce.

What happens to the remaining energy when production is greater than demand?

When the energy production from a photovoltaic system is greater than the current demand, the excess energy can be managed in several different ways, depending on the infrastructure and regulations:

  1. Sales to the power grid

    • In Poland, there are two main billing systems available to owners of photovoltaic installations:
      • Net-metering (discount system): In this system, installation owners can feed surplus energy produced into the grid and then receive this energy at a later date. The ratio of energy received to energy injected depends on the size of the installation:
        • 80% for installations up to 10 kW.
        • 70% for installations from 10 kW to 50 kW.
      • Net-billing: Under the new net-billing system, energy injected into the grid is sold at the market price and the installation owner can buy energy from the supplier at market prices. The funds obtained from the sale feed into the so-called prosumer deposit, from which the costs of purchasing power are covered in the first instance.
  1. Energy storage:

    • Excess energy can be stored in batteries. Energy storage facilities allow the stored energy to be used later, for example at night or during periods of low sunlight. This is an increasingly popular solution thanks to developments in energy storage technology and the falling cost of batteries.
  1. Energy management systems:

    • Smart energy management systems can automatically adjust the energy consumption of a home or business to increase self-consumption. For example, the system can run the washing machine or charge electric vehicles during peak energy production hours.
  1. Regulations and tariffs:

    • In some cases, surplus energy can be sold to the grid at a fixed tariff set by the energy supplier. This may be less financially beneficial than net-metering, but it is also an option.
  1. Heat utilisation (hybrid systems):

    • Surplus electricity can be used to produce heat, for example by heating systems (boilers, heat pumps). This is used in hybrid systems that combine photovoltaics with other renewable technologies.

Summary

When photovoltaic energy production exceeds demand, the surplus can be managed by:

  • sale to the power grid,
  • storage in batteries,
  • use by energy management systems,
  • sales at a fixed tariff,
  • or use for heat production in hybrid systems.

The choice of the appropriate solution depends on local regulations, available infrastructure and individual user preferences.

 

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