Optimise Your Battery, Realize Savings

Who would not say ‘yes’ to an exciting, level-up version of going solar? This article saves you all the trouble of digging through the internet in search of answer to your practical questions about residential solar system and beneficial pros of having solar battery storage. Halfway through this article, you will gain substantial knowledge on the concept of Optimization, an upgraded capability of solar battery that utilizes the cutting-edge technology of Machine Learning. Most importantly, we will clarify speculations and doubts so that you will get to the bottom of how to get more savings while enjoying the full benefits of having solar battery with Optimization.

Key Takeaways

• Through optimization, households can double their savings, with an overwhelming 800% Return-On-Investment.
• Batteries + Optimization has similar or shorter payback period than stand-alone solar systems without connected battery.
• Optimal size of battery can be calculated.

How much is a solar battery?

This is the question everyone has in mind but is often asked last. Let us dive right into the inevitable question: how much is a solar battery? Solar battery costs £350 pounds/kWh, so in a straightforward calculation, 10kWh storage capacity would cost £3500. Later in this article, our simulations use £4000 for the cost of battery storage wherein we factored-in the charging/discharging functionality cost, that’s most of the cases built into the solar hybrid inverter.
The amount is undeniably a heavy investment which necessitates careful thought. Fortunately, the UK government is bearing great news by imposing an improved regulation on taxation to promote usage of residential renewable energy. The new policy lifted the 20% VAT (Value Added Tax) on energy-saving measures including solar systems. Take note that the zero VAT will be applicable to the entire solar system (Solar panels, inverter and solar battery combined) and will not take effect if you are to purchase the components individually. The implementation of Zero-Rate VAT is till March 2027, so it is best to take advantage of the new legislation before the government amends the policy.

What is the Payback Period of having a solar battery?

Though solar batteries have tremendous advantages in terms of resilient energy supply, the trade-off is on its price tag. In a recent MSC report, the average cost of 4-10kWp solar installations without battery is at £2100/kWp with calculated payback time of an average solar system is 12 years. The average cost of solar installation went up by 31% in 2023. Meanwhile, the cost of batteries significantly went down by -20%. On the other hand, the calculated payback period of solar batteries – without optimization – is 16 years* which is based on the simulated annual savings of a household with average consumption of 4000kWh per year.

*Assumptions in the calculation: 4000kWH annual electricity usage, 4000kWh annual solar energy, £4000 battery storage cost, 15p/kWh export and 32.40p/kWh import tariff, Elexon Profile Class 1 consumption pattern, TMY weather conditions, 365days/30minute resolution

An extraordinary solution to significantly reduce the payback period and improve savings was developed by effiren batteries. By incorporating an added capability called Optimization, you will yield higher annual savings thereby cutting the payback period. The optimized battery extension -that is excluding the solar panels, cabling, solar inverter – will pay back 3 years (-25%) earlier, so the optimized battery is smarter choice than the solar investment in 2023. There are two types of Optimizations, both of which can get you higher annual savings than conventional solar batteries. You can see the incremental savings for each type in the Stack Graph below:

Semi Optimisation: Semi-optimisation has subscription cost amounting to £20/year. With this minimal yearly subscription cost, the payback period is reduced to 9 years.
Full Optimisation: With a cost adder of £30 per year for the Full Optimization, you can enjoy twice the savings you get from solar batteries without optimization. The additional yearly subscription is due to the added Machine Learning feature on the batteries. With £4000 investment on solar battery without optimisation, you can get roughly £240 cost savings. With Full-Optimisation, you will get another £240 annual saving which mean you can get similar payback time as with a solar system without battery. The incurred savings far outweigh the additional investment required.
For users that have solar and battery installation already, the optimization can be purchased as subscription. You can grab our free trial version and we can enable our system to communicate with your already-installed system.
The above-mentioned savings are calculated based on the highest available export tariff in the market and that’s 15p/kWh (Octopus Outgoing Fixed tariff). If you’re still availing the Smart Export Guarantee (SEG) tariffs (4.9p/kWh), we recommend switching to Octopus Outgoing Fixed tariff to get tripled savings.

How does optimization work in solar battery storage and what are the advantages?

As solar technology is highly dependent on the weather changes, solar battery that is equipped with Optimization has predictive capability to operate at its best state based on weather forecasts. We dislike the trouble of having an empty battery in the morning when the sky is cloudy nor having an already-full battery when the day is sunny. Optimization strikes the balance on these weather inconsistencies through AI. Cool optimization, right?

Since household activities and power usage are usually aligned to the rhythmic pattern of day and night, optimization technology can keep track of your power usage to understand the right timing to export and import energy. One of the main benefits of using batteries is being able to shift the generated solar energy (during the day) to be used when it is needed mostly in the evening. Generally speaking, electricity is cheap when the demand is low (at night) and expensive when the demand is high (late afternoon/early evening). Time-Of-Use (TOU) Tariffs are available luckily for a while to households as well, so it is not for big commercial users only. Looking at the tariff shape, it looks obvious to utilize the battery with grid charging/discharging if there is not enough solar energy generated or when it is more than the daily usage. With this added capability, energy savings are even more maximized. The mechanism is best-explained by the 24-hour snapshot of energy rates plotted in a time-series graph below.

The peak and the valley on the graph represent the range of hours when the load rate is the least and most expensive. Concurrently, the graph shows the best time to charge and discharge your battery. In other words, and to put in a simpler acronym— “EEII” which means Export when the rate is Expensive and Import when the rate is Inexpensive. In this manner, soaring electricity bills are avoided and savings are maximized.
Let us discuss in detail how the two types of Optimization differ. In Semi-Optimization, the system analyzes monthly weather condition from Typical Meteorological Year (TMY) and average state-of-charge (SOC) value for the month. The system is doing a one-time calculation as basis for the optimization.
On the other hand, solar battery paired with Full Optimization has a built-in AI-based algorithm that enable users to boost savings by analyzing daily weather forecast, historical energy consumption of the household and state-of-charge (SOC). The historical energy usage is being recorded on a 30-minute resolution. The system captures the data everyday for more accurate prediction.
Without optimization, you are missing the above factors thereby incurring higher cost and wasting the full potential of solar battery capacity.

What inverter types are compatible with effiren batteries?

The effiren solar battery has a wide range of inverter compatibility. There are two types of compatibility, 1: With inverter, we are compatible with every major brand on the market, while the 2: optimization is compatible with Victron, DEYE inverters. The firmware of our solar batteries can be changed to make them compatible with the inverter of your choice. Although our solar batteries are flexible, we recommend inverter brands that are reliable and known to work well with effiren. Coupling our solar batteries with our recommended inverters will help you actualize full savings.

What is the warranty coverage and period?

Another main consideration in acquiring solar system is understanding its warranty period. Warranty coverage grants you peace of mind in anticipation to unexpected issues on the unit. The warranty of solar batteries is defined based on the number of years and the number of cycles (charging and discharging of the battery). The effiren solar battery warranty period is 10 years and/or 6000 cycles of charging and discharging. The expected and designed lifetime is 15 years. Our solar batteries are maintenance-free so there is no after-sales service.

What should I do to avoid losing the warranty, get the most out of the battery and increase its lifetime?

It is also critical to tackle how you should properly use solar batteries to avoid losing the warranty. Being mindful of the do’s and don’ts help you ensure the lifetime of the battery. First, is the temperature condition. You should keep the solar battery at room temperature, ideally at 20 to 25⁰C, hence, you must refrain from installing your solar batteries outdoors. Exposing the batteries in temperatures ranging from 40 to 45⁰C will deplete one-third of the product’s lifetime. Hence, you must avoid installing the batteries outdoors. Another consideration is the so-called Depth of Discharge “DOD” limitations of solar batteries. Sustaining 80% of battery charge will help double the lifetime of the battery.

What is the optimal size of the battery?

Keep in mind that knowing the optimal size of your battery is critical as it translates to savings, shortened payback period and longer battery life. It was earlier mentioned that import and export of energy highly rely on the pattern of day and night. Similarly, some expected trends can also be observed on import and export of energy with the changing of seasons.
On the winter months, import of electricity is higher due to power demand surge and lower solar generation. On summer months, export is higher due to increased solar generation. The optimum battery storage size is at the point where the export and import levels are the same. This happens during spring and autumn months. In our example, the optimum value for the size of the battery is 6kWh.
The size of the solar PV should also be taken into account when considering the optimal size of the battery. The recommendation is to oversize the battery by 30% to get shorter payback and ensure reserved capacity. Oversizing also helps double the lifetime of the battery.

What are the key differences between good quality and bad quality battery storage

There are 3 main components of LFP (Lithium iron phosphate) battery quality: BMS (Battery Management System), quality and lifespan of battery cells, and the overall quality of the assembly of these components.

As for the BMS, if the built-in protection and safety functions work and is capable to keep the pack in balance, the BMS part is fine. The real difference is in the cell level quality. The difference in cycle time even among good quality battery cells can be two to three-folds, so without knowing the cell type and its manufacturer, it is difficult to evaluate the final quality. Our batteries are equipped with either EVE or CATL cells which are proven to perform the highest cycle time. The cell level cycle time and battery module level cycle time are two different things. As you connect several cells in series or parallel, the cycle time decreases. Some battery manufacturers claim higher cycle time than the cell can perform. The reason behind this is that these batteries warranty policy is for residential solar applications where the charging rate, DOD are both lower than the manufacturer reported test conditions.

Another thing to note in battery quality is temperature. A medium size (105Ah) battery cell can perform 50% less cycles on 45⁰C compared to the optimal 25⁰C. We do not recommend using batteries without HVAC system installed outdoors.

The truth is, battery cycle time can be determined only when these 4 usage conditions are satisfied: 1) Ambient temperature, 2) C-rate (charging/discharging rate) 3) Depth of Discharge DOD and 4) Remaining capacity (SOC/SOH). If any of these 4 conditions changes, the cycle time changes. So, saying x thousands of cycle time in marketing papers without explaining these 4 relevant parameters, means you are just looking at the tip of the iceberg.

We found one value that can predict the real lifespan quite accurately, that’s the energy throughput value. Watch out, there are companies who count the charging and discharging values as well, so they double their cycle time in this way – again it’s marketing game.

Humans aren’t the only ones who age through time, batteries do as well. Calendar life is the last factor that define battery life. Batteries degrade as time goes by so even if you use your battery only with daily 1 cycle, after 10 years it would reach 3650 cycles. If your performance warranty is 6000 cycles, you can think that you have reached only the 60% of the lifespan, unfortunately that’s not the case. With the calendar aging, your will reach more than that.

We have explained and detailed the answers to the commonly asked questions about solar batteries and optimization technology. As knowledge and information are prerequisites prior investing on anything, you are now more aware and empowered to choose the best product that suits your needs. Solar battery with Optimization might be your best decision yet.

If you want to see the battery charging/discharging pattern with an hour resolution, you can check the result of our simulation of a typical year below.