Solar-powered auxiliary batteries: Why are they now a necessity?

Last summer, news broke from a residential area that the electricity bills for homes with solar panels were approximately 30% lower year-over-year in August. However, the battery system in that home was a standard battery installed in 2023. This indicated that even simple solar panel installation could significantly reduce electricity bills. However, many households still don't understand why their electricity bills don't decrease significantly after installing solar panels. Especially during peak electricity demand in winter, the problem of power outages during times when the panels aren't generating electricity remains unresolved.

In this reality, adding a backup battery (energy storage system) to solar systems is no longer just an option, but a necessity. Especially with changes in electricity pricing structures and government subsidy programs, operating solar systems without batteries can be detrimental in the long run.

---

How does electricity cost change when using solar without a battery?

Generally, homes with solar panels generate electricity between 9 AM and 5 PM. However, most households experience peak electricity usage between 6 PM and 10 PM. Since solar panels don's operate during these hours, electricity must be purchased from the power company. Using electricity during peak evening hours can actually increase electricity bills.

For example, let's say a home has a 10kW solar panel system. During the day, it generates 40 kWh of electricity, which is all used, and the remaining 20 kWh is sold back to the grid. However, the household then needs to purchase 35 kWh in the evening. If the cost of electricity purchased from the grid is higher than the price received for selling electricity during off-peak hours, the overall electricity bill can actually increase.

---

How does actual electricity usage patterns change when installing a backup battery?

With a backup battery, you can store more than 70-80% of the electricity generated during the day. This means you can use that solar-generated electricity directly or consume it in the evening. In fact, many homes with batteries have seen their electricity purchases from the grid reduced by more than half because they use solar power during the day and then switch to battery power in the evening.

Furthermore, under the recently introduced time-of-use electricity pricing structure, households that utilize batteries are economically advantageous because they can use battery power during the hours when electricity is most expensive. Operating solar systems without batteries results in a repetitive "careless consumption" pattern where electricity is used up during the day and then repurchased in the evening.

---

What are the key criteria to consider when choosing a battery?

It's risky to only look at "the cheapest option" when choosing a battery. In reality, battery lifespan and cycle count are the most important factors to consider.

• Lithium-ion batteries (Li-ion) are compatible with most solar systems and typically last for more than 10 years.
• The cycle count (number of charge and discharge cycles) should be at least 6000 to ensure long-term stability.
• The energy capacity should be determined based on the household's average daily electricity consumption. For example, a household that consumes 20 kWh per day should consider a battery with a capacity of 15-20 kWh.

Also, be sure to check the safety standards. A well-designed battery should have a good thermal management system (to prevent oxidation and overheating), and it's beneficial if it has wireless remote monitoring capabilities for early detection of any issues.

---

Is the timing right to install a battery, given the changes in government subsidies?

As of 2024, the government is shifting its policy to expand subsidies for solar + battery combinations. Previously, only solar panel installations were subsidized, but now, a program is in place that subsidizes 30-50% of the cost of installing a battery. This is a key condition that reduces upfront installation costs.

Furthermore, as policies to enhance grid stability through the integration of solar and batteries are being strengthened, households that operate both solar panels and batteries together are likely to be recognized as contributors to peak load reduction on the grid.

---

Operating solar without a battery can be detrimental in the long run.

Solar panels are a great starting point, but the problem of mismatched electricity production and consumption cannot be solved without a battery. Especially with the current time-of-use electricity pricing structure, there are limitations to reducing electricity bills solely through solar power.

The main role of a battery is to bridge the gap between electricity demand and supply. This helps stabilize electricity costs, reduces strain on the grid, and ultimately contributes to increased energy independence.

Practical Advice: When planning a solar system, aim for a battery capacity that is 60-70% of the household's average daily electricity consumption. While it's possible to install solar panels without a battery, remember that more than 70% of the electricity cost savings come from the battery.