Residential Solar Storage Systems - Comparison

Introduction

We offer two residential battery storage systems:

• Tesla Powerwall 3
• Sigenergy SigenStor

We have presented a comparison of our offering in the tables below.

Both the Powerwall 3 and SigenStor are 'all-in-one' systems, with the inverter, charger, and battery combined into a single unit. This makes for a compact, clean installation with simplified monitoring and control.

There is no 'one-size-fits-all' solution. The right choice will depend on your budget, space availability, household consumption, solar output, and whether you want backup power in a power cut.

Storage Cost / Benefit

Installing battery storage affords the following potential benefits:

• Increased on-site use of solar generation, with a correctly sized system, 65–80% of solar generation should be used on site, reducing your electricity bill
• Emergency power supply in a power cut
• The ability to buy electricity off-peak and store it for use during peak hours
• The potential to increase on-site power output by around 20%, useful when fast-charging an electric vehicle
• The potential to access future opportunities including the export and sale of electricity at peak times, and the provision of grid balancing services

Both the Powerwall 3 and SigenStor use lithium iron phosphate (LFP) battery chemistry, which offers a longer cycle life than older lithium manganese cobalt (LMNC) chemistries, typically around 10,000 lifecycles versus 4,000, and contains no cobalt. With a correctly sized system, the lifetime cost per kWh of stored electricity is around 9p per kWh, compared to an average domestic grid cost of around 22.36p per kWh.

The lifetime cost per kWh assumes an expected battery lifetime of between 10 and 25 years, and whilst the overall economic case is favourable, battery storage should be seen as a long-term investment.

System Comparison: Rough Cost, Use, Components and Sizing

System Comparison: Normal Operating Modes / Functionality in a power cut (Islanded Mode)

It is important to know what happens in a power cut. Does the storage system work? Does the solar PV still work? Will everything in the house work ('Whole House' back up), or just pre-defined 'Emergency' loads connected to a separate board?

Note that all of this functionality is subject to prior approval from the network operator (SSE, Western Power etc).

System Comparison: Monitoring, installation and warranty

System Comparison: Three phase (400V) grid connections

If you have a normal single phase (230V) grid connection, ignore this section.

With a three phase grid connection, you have a choice:

• connect storage to one of your three phases only, in which case only loads and single phase PV inverters connected on this phase will work in a power cut; or
• connect storage to all three phases, which is more expensive, but, with Victron (or GivEnergy's commercial three phase storage units), will enable you to back-up all three phases.
  
  

  	Tesla Powerwall 3	Sigenergy SigenStor
  Can the system be installed on a three phase connection?	Yes, one Powerwall 3 per phase, plus 3 expansion packs per Powerwall 3 unit. Power cut protection capability on three phase connection unknown.	Yes, up to 50 units.
  Will the system work in a power cut?	Yes, on a single phase. 3 phase power cut protection support coming coon, according to Tesla.	Yes, with both single and three phase support. With the maximum capacity (1ph - 192 kWh. 3ph - 2.4MWh).