In the UK, hundreds of thousands of domestic and small commercial solar systems have been installed. Over the past two years, more and more of these systems are being retro-fitted with a solar energy storage system to help maximise the benefits of solar PV generation. In several cases, the size of the original solar system is being extended.
Solar battery storage has the potential to solve the problems of intermittent supply of renewable energy (mainly solar and wind):
Installing storage affords the following potential benefits:
In economic terms, with the correctly sized system, the lifetime cost per kWh of stored electricity is around 12p per kWh. This compares to an average domestic grid cost of around 16p per kWh, and an average expected cost of around 25p – 30p per kWh over the life of a typical storage system.
The lifetime cost per kWh typically assumes an expected lifetime of between 10 years and 25 years (or 3,000 – 10,000 lifecycles), and whilst the overall economic case is favourable, solar energy storage should undoubtedly seen as a long-term investment.
There is no “one size fits all” solution in battery storage. When designing a solar storage system, our final recommendation needs to take into account sizing (excess electricity from the PV system, on site usage) and functionality, in particular whether or not an emergency power supply is required and whether or not the PV needs to function in a power cut. These requirements inevitably impact budget.
Having said that, we have identified the technologies we believe to be “best in class” for solar energy storage. They are listed here, with links to further details.
Inverter / charger technology:
Our favourite inverter chargers are Victron and SMA. SolarEdge also provides a product called StorEdge, directly compatible with SolarEdge solar systems and indirectly with any solar PV system using an additional inverter.
|Is the Tesla Powerwall 2 right for me?|
The installed cost of Tesla Powerwall 2 is around £7200 + VAT. Storage capacity is around 13.5kWh and so this gives a cost of around £533 + VAT per kWh.
This is about as competitive as it gets … on a cost per kWh basis, pretty much every other system will be a similar cost or more expensive. Note that in general lithium ferro phosphate (LFP) – in other words Sonnenbatterie and Simpli-Phi – is more expensive than lithium manganese cobalt (NCM) – in other words Tesla and LG Chem. But the LFP batteries offer 10,000 life cycles (25 – 30 years on most usage cycles) as opposed to 15 years.
For more information on costs and lifetime performance analysis, and for a detailed technology comparison, download our Guide to Residential Solar Storage: