Solar battery review
| 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
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
Calculations
| 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 |
Assumptions
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)