The energy storage inverter has three major functions, including peak regulation, backup power supply and independent power supply. From a regional perspective, peak shaving is a demand in Europe. Taking Germany as an example, the electricity price in Germany has reached 2.3 yuan/kWh in 2019, ranking first in the world. In recent years, German electricity prices have continued to rise. In 2021, the electricity price for German residents has reached 34 cents/kWh, while the LCOE of photovoltaic/photovoltaic distribution and storage is only 9.3/14.1 cents/kWh, which is 73%/59% lower than the residential electricity price. The difference between the cost of photovoltaic power distribution and storage will continue to widen. Household photovoltaic distribution and storage systems can reduce electricity costs, so users in areas with high electricity prices have a strong incentive to install household storage.
In the peak shaving market, users mostly choose hybrid inverters and AC-coupled battery systems, which are more cost-effective and easier to manufacture.
Off-grid battery inverter chargers with heavy-duty transformers are more expensive, and hybrid inverters and AC-coupled battery systems use transformerless inverters with switching transistors. These compact, lightweight inverters have lower inrush and peak power output ratings, but are more cost-effective, cheaper and easier to manufacture.
The backup power supply is needed by the United States and Japan, and the independent power supply is just in demand in the market, including South Africa and other regions.
According to EIA, the average power outage in the United States in 2020 will exceed 8 hours, mainly due to the scattered living of American residents, the aging of some power grids, and the impact of natural disasters. The application of household photovoltaic distribution and storage systems can reduce the dependence on the power grid and increase the reliability of power supply on the user side. The photovoltaic energy storage system in the United States is relatively large and equipped with more batteries, because it needs to store electricity to deal with natural disasters. Independent power supply is just a market demand. South Africa, Pakistan, Lebanon, the Philippines, Vietnam and other countries have tight global supply chains, and the national infrastructure is not enough to support the public’s electricity consumption. Therefore, users must equip household photovoltaic energy storage systems.
Hybrid inverters have certain limitations as backup power.
Compared with dedicated off-grid battery inverters, hybrid inverters have some limitations, mainly limited inrush or peak power output during blackouts. Additionally, some hybrid inverters have no or limited backup power capability, so only small or essential loads such as lighting and essential power circuits can be backed up during a power outage, and many systems experience a 3-5 second delay during a power outage. Whereas off-grid inverters provide very high inrush and peak power output and can handle highly inductive loads. If the user plans to power high surge equipment such as water pumps, compressors, washing machines and power tools, the inverter must be able to handle the high inductive surge loads.