Solar battery review 2017-11-22T16:05:28+00:00

Solar battery review

Solar batteries
Manufacturer Cooling system Warranty (years) Usable capacity (kWh) Continuous power (kW) Price per kW
Pylon Tech 2.4 None 10 2.0 increments 1.2 per battery 373
Tesla Powerwall Water and fan 10 13.4 5.0 385
BYD 10 None 10 9.8 10.0 429
Mercedes 12.5 Fan 10 11.5 4.6 438
LG RESU10 Fan 10 8.8 5.0 479
Victron 2.4 None 3 2.1 increments 2.0 per battery 862
Moixa 3 Fan 7 2.4 0.43 1,041

Table updated 21 November 2017

Cooling system

The most important item is the cooling system, since it impacts battery life significantly. Fan or water cooling should prolong the life of the batteries.


Warranty is extremely important, since it will massively impact how environmentally friendly the system is and also the financial benefit.

Usable capacity

Most manufactures quote nominal battery capacity, which is irrelevant since it is usable capacity that matters. Usable capacity should be matched to the PV system size and the demand for electricity in the home.

Continuous power

If you have a load of 3kW such as an immersion heater or kettle, a system with maximum continuous output of 2kWp will pull energy from the grid, making the storage system less effective.

4kW+ PV system

Tesla Powerwall 2 AC

  • 13.4kWh of capacity ideally suited to 4kW of PV.  Typically providing 2 nights of power when fully charged.

  • Expected longer battery life due to liquid and air cooling

  • Simple design

  • 3.6kW (5.0 kW with permission from Western Power Distribution) of continuous power to run immersion heater and kettles which are typically 3kW

  • 10 year warranty on battery

  • Expected longer battery life due to liquid and air cooling

2kW PV system

LG 3.3kWh

  • 2.75kWh of usable capacity ideally suited to 2kW of PV.

  • Can be matched to many battery inverter/chargers such as Goodwe, SMA and SolarEdge

Electric car, electric Aga or hot tub

Tesla Powerwall 2 AC

  • The 13.4kWh Tesla Powerwall 2 is suited to charging the large electric car batteries of 30kWh+.

Regular powercuts

Wait for Tesla to release backup system expected in March 2018

  • The Tesla Powerwall system can be installed as a backup system in many other countries and Tesla are hoping an agreement can be reached with the Distribution Network Operators to make it easy in the UK.

Expected savings

The expected savings for the average 3 bedroom home is £344 per year


Assumption Unit Value
Energy from PV system kWh 4,328
Current use of PV in home 35%
Use of PV in home with battery 85%
Units of energy saved kWh 2,164
Financial benefit of energy saved £ 344


  • Cost of electricity is 16p per kWh

  • South facing system installed in Devon and Cornwall at 30 degree pitch

  • Electricity prices fixed (increased energy prices would increase the savings)