With solar batteries like the Tesla Powerwall starting to feature in the media it can be hard to get to the bottom of whether you should invest in solar batteries or not. This solar battery calculator, intended for those with a UK grid connection, can help show the likely benefit for your own solar system. You can use it to see how much you lose on your investment by buying solar batteries in 2018. It calculates how much of your own solar generated electricity you are able to store in batteries for later re-use.
Use the sliders to adjust the calculator to reflect your own solar installation. The Energy stored per year data is calculated using a real 12-month period of solar generation to represent the day-to-day fluctuations in solar output throughout the year.
The default positions are set for a typical 4kWh solar PV system with average output of 850kWh per year per kW of panel with 50% of generated energy available for export or storage for later use. We have assumed a 2kWh solar battery with a 5 year warranty and an installed cost of £2,500.
Update: July 2019
An alternative version of the calculator, allowing for SEG payments, is also available. See Solar Panel & Battery Storage Calculator.
Or just adjust the slider until the generated per year figure in the right hand column matches your annual solar electricity output.
Summary Of Results
We would be delighted to get suggestions for improving this calculator via the comments section below. At the moment we assume energy prices stay broadly flat over the battery warranty period. Those who predict huge rises in electricity prices in the future may be right but on balance we think they are wrong. Cheap battery storage will be a game changer on energy pricing. Solar battery systems are quite quick to install; it’s best to wait until you make money today rather than buy on projected future energy prices. Battery prices are likely to fall in the next few years anyway; if energy prices double or treble then that’s the time to re-calculate the likely benefits.
UK Solar Batteries
Below is a list of some of the solar battery products that are visible in the UK market. Estimated prices are the likely fully installed cost of a battery storage system using this product. These prices are different to headline prices of the uninstalled storage unit in isolation. We are happy to receive updates on prices as they fall.