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Investing in solar battery storage offers numerous benefits, from reducing energy bills to increasing energy independence.
Solar batteries have greatly improved in recent years, becoming more efficient and durable while providing a cost-effective solution to maximise the energy efficiency of your solar panel system.
Before you make a purchasing decision, consider different batteries’ capacity, efficiency, warranty, and cost. We think the best battery on the market right now is the Tesla Powerwall 2.
In this comprehensive solar battery storage guide, our experts explain everything you need to know to take full advantage of free solar energy.
This is a versatile residential battery that is ideal for storing excess solar energy, but it also works efficiently without a solar array.It enables users to store energy from the grid when it’s at its cheapest, for later use, providing backup power and reducing reliance on peak-time electricity. This flexibility makes this battery a popular choice for homeowners; 14 per cent of our survey respondents* own a Tesla solar battery.
For those needing more power than the 13.5kWh offered, you can install up to 10 units of the Powerwall 2, giving you a combined storage capacity of 135kWh. Each additional Powerwall increases storage capacity and boosts the system’s charge and discharge power, enhancing overall performance. While this is well beyond the needs of most households, it may be relevant for larger homes or businesses.
This battery is an affordable solution to solar energy storage, with a neat, compact design, making it ideal for smaller spaces. Of our survey respondents*, 11 per cent have a Sunsynk solar storage battery.
However, while it offers solid performance for storing excess solar energy, with a small usable capacity of 4.6kWh, multiple units may be necessary for more considerable energy demands.
With a substantial energy storage capacity, this battery comes with a competitive unlimited-cycle warranty. It’s designed to integrate seamlessly with SunPower solar panels, but it can also work with third-party solar panels, provided they are paired with a compatible inverter.
A single SunVault battery stores up to 19.5kWh of energy. If more storage is needed, an additional unit can be installed, doubling the capacity to up to 39kWh.
According to our survey results*, SunPower is the most popular battery brand, owned by 20 per cent of respondents.
With an efficiency of more than 96 per cent, the Generac PWRcell is our pick for the most efficient solar storage battery.
Unlike typical battery boxes, the PWRcell stores energy using a battery cabinet that can house up to six lithium-ion battery modules. The number of modules in the cabinet determines the storage capacity; if you need a higher capacity, you simply purchase a new battery module instead of a whole other battery.
This battery comes with a standard 10-year warranty. However, joining the Gridshare programme extends this to an unlimited warranty. Gridshare allows users to trade excess stored energy with the grid for £50 annually for the first three years, and a 50 per cent share of profits from exported electricity after that.
While earnings are likely to be small compared with the Smart Export Guarantee, the unlimited warranty makes this scheme very appealing.
| Tesla Powerwall 2 | Sunsynk L5.1 | SunPower SunVault | Generac PWRcell | Moixa Smart Battery | |
|---|---|---|---|---|---|
| Cost | £6,500 – £8,000 | £1,200 – £1,800 | £10,000 – £12,000 | £8,000 – £10,000 | £4,500 |
| Total storage capacity | 14kWh | 5.12kWh | 19.5kWh | 18kWh | 4.8kWh |
| Usable capacity | 13.5kWh | 4.61kWh | 13kWh | 9kWh | 4.08kWh |
| Efficiency | 90% | 90% | 86% | 96.50% | not specified |
| Depth of discharge | 100% | 90% | 92% | 84% | 85% |
| Power output | 7kW | 7.5kW | 12kW | 7.6kW | 2.4kW |
| Warranty | 10 years | 5 years | 10 years | 10 years | 10 years/unlimited |
| Type of battery | Lithium-ion | Lithium-iron phosphate | Lithium-iron phosphate | Lithium-ion | Lithium-iron phosphate |
When choosing a solar battery, you should consider several factors to ensure it meets your energy needs without drastically impacting the cost of your solar system.
To select the best home battery storage systems, our solar energy experts assessed 40 models from 18 brands. We evaluated various factors crucial for performance, reliability, and value. Key criteria included:
We also surveyed more than 1,500 The Independent readers who own solar systems* to find out their motivation for installing solar battery storage and whether they were satisfied with their systems.
Finding the best deals on solar panels and batteries will help you maximise your investment.
The best solar batteries for winter are those with high efficiency and good cold-weather performance, such as lithium-ion phosphate batteries, which perform well in low temperatures. The Tesla Powerwall 2 is known for its durability and ability to store excess energy for use during shorter daylight hours in winter.
Battery storage supports EV charging by storing excess energy from solar panels or the grid during off-peak hours, making it available for charging electric vehicles when needed.
The lifespan of a solar battery typically ranges from 10 to 15 years, depending on factors such as the type of battery, usage, and maintenance.
When solar batteries are full, any excess solar power is typically sent back to the grid, if connected, or may be curtailed to prevent overloading.
The best way to store solar batteries is in a cool, dry, well-ventilated area, to prevent overheating and prolong their lifespan. Avoid exposure to extreme temperatures and ensure proper maintenance checks to maximise battery performance and longevity.
A bigger solar battery isn’t always better; it depends on your energy needs and usage patterns. While larger batteries provide more storage capacity, they are also more expensive. The extra capacity may be well-spent if you generate or use enough energy to fill and deplete the battery regularly. Matching the battery size to your household’s solar generation and consumption is essential for maximum efficiency and cost effectiveness.
