Residential Storage Overview

Introduction

We offer four different residential storage systems, as follows:

Tesla Powerwall 2
MyEnergi libbi (NEW Jan 2023)
GivEnergy domestic and commercial systems (domestic - Modular + All in One)
Victron Energy Storage Systems (Victron + BYD / Pylontech batteries)
Tesla Powerwall 3 coming when released

We have presented a comparison of our offering in the tables below. You can also download this comparison as a PDF.

All storage systems consist of a charger and battery. The Powerwall's and libbi are 'all-in-one' systems, with the charger and battery combined into one unit. The GivEnergy and Victron systems have separate charger and battery units, making them less compact and aesthetically pleasing, but more 'modular' with greater design flexibility.

There is no 'one-size-fits-all' solution. The right choice for you will depend on your budget, space availability, house usage, solar output, and whether you want a back-up in a power cut or not. You may not want cobalt in your battery, in which case the Powerwall is not for you.

Storage Cost / Benefit

Installing storage affords the following potential benefits:

increased on-site use of solar generation – with a correctly sized solar energy storage system, 65%-80% of solar generation should be used on site, thus reducing the owner’s electricity bill;
emergency power supply in a power cut;
the ability to buy electricity off-peak and store it for use at peak;
the potential to increase on site power output by around 20% (useful when fast-charging an electric vehicle);
potential to access future opportunities including the export and sale of electricity at peak charge times, and the provision of grid balancing services.

A re-chargeable battery essentially consists of thousands of 'kWh storage slots', charging one kWh by the grid or excess solar, and then discharging one kWh (minus about 10% losses). In economic terms, one of the key questions is - how much does each kWh storage slot cost? The answer depends on the chemistry, since lithium ferro phospate (LFP) typically offers twice as many 'lifecycles' or storage slots per kWh battery capacity than lithium manganese cobalt (LMNC). With the correctly sized system, the lifetime cost per kWh of stored electricity is around 9p per kWh for LFP (all our batteries except the Powerwall) and around 16p per kWh for lithium manganese cobalt (Powerwall). This compares to an average domestic grid cost of around 34p per kWh.

The lifetime cost per kWh typically assumes an expected lifetime of between 10 years and 25 years (or between 4,000 lifecycles (LMNC) and 10,000 lifecycles (LFP), and whilst the overall economic case is favourable, solar energy storage should undoubtedly be seen as a long-term investment.

System Comparison: Rough Cost, Use, Components and Sizing

	Tesla Powerwall 2	Tesla Powerwall 3	MyEnergi libbi	GivEnergy Modular	GivEnergy All in One	Victron + BYD/Pylontech
Rough Installed Cost (ex VAT) VAT is 0% if installed domestically with solar panels, 20% otherwise	£ 7350 + VAT £544 per kWh storage ~ 16p per kWh storage 'slot'	TBC - Not yet announced, we predict £12,000 - £15,000	3.6kW / 5kWh: £ 6500 + VAT 5kW / 20kWh: £ 14500 + VAT from £788 per kWh storage from 9p per kWh storage 'slot'	HY5.2 +9.2kWh:£6600 + VAT AC3.0 +5.2kWh:£ 4750 + VAT HY5 +19kWh: £ 9600 + VAT from £632 per kWh storage from 9p per kWh storage 'slot'	£ 7800 + VAT from £424 per kWh storage from 9p per kWh storage 'slot'	Varies: e..g. Quattro 8000 + 15.4kWh BYD: £ 14000 + VAT from £909 per kWh storage from 9p per kWh storage 'slot'
Chemistry⁽¹⁾ Typical number of lifecycles for this chemistry	Lithium Manganese Cobalt ~ 4,500	TBC	Lithium Ferro Phosphate ~6,000 - 10,000	Lithium Ferro Phosphate ~6,000 - 10,000	Lithium Ferro Phosphate ~6,000 - 10,000	Lithium Ferro Phosphate ~6,000 - 10,000
Back-Up Capability⁽²⁾ (for a standard 230V grid connection)	'Whole house backup or emergency loads; solar works in a power cut.	'Whole house backup or emergency loads; solar works in a power cut.	Emergency loads backup only (optional extra to price shown).	Emergency loads backup only (limited to 2.5kW). Solar limited in a power cut.	'Whole house backup or emergency loads; solar works in a power cut.	'Whole house' backup or emergency loads; solar works in a power cut.
Use Case⁽³⁾ AC coupled: add storage to an existing PV system? DC coupled: install storage and solar using the same inverter for battery and PV? Mix DC coupled and AC coupled?	Yes No No	Yes Yes TBC	Yes Yes Yes	Yes (use GIV-AC3.0) Yes (use GIV-HY) No	Yes No No	Yes Yes Yes
System Accepts Generator Connection?	No	TBC - (unlikely)	No	No	No	Yes - Quattro allows for grid and / or generator plus battery.
Size Per Unit Max AC Output Power(sizes are per unit - see below for units per phase)	3.68kW / 5.0kW⁽⁴⁾	11.5kW - Specifics unknown	3.68kW / 5.0kW⁽⁴⁾	AC AC Coupled:3.0kW⁽⁵⁾DC Coupled:3.0kW⁽⁵⁾/ 5.0kW	6.0kW	Various units, from 3.0kW to 12.0kW
Battery capacity Per Unit Note the most useful capacity is usable capacity (nominal x 80% - 90% depth of discharge = DofD x Nominal	Usable: 13.5kWh	Usable: 13.5kWh	Nominal: Choice of 5kWh / 10 kWh/ 15 kWh / 20 kWh Depth of discharge: 90% Usable: Choice of 4.5kWh / 9kWh / 13.5kWh / 18kWh	Nominal: Choice of 2.6kWh / 5.3kWh / 9.5kWh Depth of discharge: 80% Usable: Choice of 2.1kWh / 4.2 kWh / 7.6 kWh	Usable: 13.5kWh	Choice of: BYD: 15.4kWh battery (usable capacity 15.36kWh). Pylontech offers a range, typical usable capacity being circa 2.1kWh.
Max No of Units per Phase *(Most domestic properties have one phase - 230V).*	Up to three: allows 40kWh storage capacity with 15kW power.	Up to 40.5kWh	One: allows 20kWh storage capacity, with 5.0kW power.	One inverter, up to 5 batteries: allows up to 38kWh storage capacity, with 5kW power	Up to three: allows 40kWh storage capacity.	Up to six inverters: system design allows up to ~ 90kWh storage capacity, 30kW power.

(1) Lithium ferro phosphate is a superior chemistry to lithium manganese cobalt for two reasons:
a) It offers many more lifecycles (one lifecycle being a round-trip in and out of a kWh) – i.e. many more storage slots. Typically 6,000 – 10,000 lifecycles for lithium ferro
phosphate, compared to 4,500 for lithium manganese cobalt.
b) There are reports of possible child labour issues associated with cobalt mining. Therefore lithium ferro phosphate is generally preferred.
(2) Emergency Loads require a second distribution board separating emergency loads from non-emergency loads. Whole House does not require this; however in a power-cut
usage will be limited to the power output of the storage system. Setting up a second distribution board with loads that will function in a power cut is best practice (and
good discipline!) but the additional electrical work does increase upfront cost.
(3) Solar PV panels generate DC electricity, and batteries charge and discharge with a DC current. DC coupled storage systems allow you to combine the solar PV and battery
storage into one inverter; AC coupled storage systems do not. DC coupled systems are ideal for new or extension PV installs. They are most efficient, keeping AC/DC
conversion losses to a minimum, and they also reduce the upfront system cost and the on-going maintenance cost. AC coupled storage systems are best used when retrofitting storage to an existing solar system. Flexible (AC and DC Coupled options) systems allow for both AC and DC coupled solar. They offer the best of both worlds.
(4) 5kW can be limited to 3.6kW if required by DNO operator (SSE etc),
(5) Reduced to 2.5kW for emergency loads in a power-cut. Further limited in a power cut to 1.3kW with 2.6kWh battery.

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).

	Tesla Powerwall 2	Tesla Powerwall 3	MyEnergi libbi	GivEnergy Modular	GivEnergy All in One	Victron + BYD/Pylontech
Normal Operating Modes - Self-Consumption - Timed (grid) charge / discharge - Reserve specified % for back-up	Yes Yes Yes	Yes Yes Yes	Yes Yes No	Yes Yes Yes	Yes Yes Yes	Yes Yes Yes
Scope of Back-Up⁽²⁾	Total flexibility: Whole House or Emergency Loads	Total flexibility: Whole House or Emergency Loads	Emergency Loads Only - but as an Optional Extra (non-standard).	Emergency Loads Only (up to 2.5 kW – See ⁽⁵⁾ above)	Total flexibility: Whole House or Emergency Loads	Total flexibility: Whole House or Emergency Loads
Does the system provide an uninterrupted power supply (UPS)?	No	No	No	No	Yes – 20 milli seconds	Yes – 20 milli seconds
Will the Solar PV work in a power cut?	^Yes	Yes	No	Giv-AC 3.0: No Giv-Hy: only if the inverter sees a minimum load of 50W via the emergency power supply.	^Yes	Yes
Max Solar PV system that can be installed to operate in a power cut	7 kWp (more solar can be connected 'upstream')	13.8kWp	N/A	N/A	7.2kWp	The 1:1 Rule applies (similar to Powerwall). Same size PV system as inverter rating.

System Comparison: Operating modes, functionality and warranty

	Tesla Powerwall 2	Tesla Powerwall 3	MyEnergi libbi	GivEnergy Modular	GivEnergy All in One	Victron + BYD/Pylontech
Monitoring	Tesla APP	Tesla APP	Monitoring portal and APP	Monitoring portal and APP	Monitoring portal and APP	Monitoring portal, APP and local touch screen.
Internal or External installation?	Either	Either	Inverter / battery: either, but not in loft. Controller: must be indoors.	Either (although install canopy over the inverter outside to avoid direct sunlight or rainfall).	Either	Indoors, with batteries close to inverter-charger to minimise dc cable run.
Wall-mounted or floor-mounted?	Either Stacking kit available for multiple Powerwalls	Either Stacked up to 40.5kWh - Specifics of stacking unknown	Either	Wall-mount the inverter, batteries can be floor-standing indoors or wall-mounted indoors and outdoors.	Either	Inverter-charger is wall mounted, batteries are floor-standing.
Warranty	10 year defects. 80% storage capacity retained after 10 years.	10 year defects. 80% storage capacity retained after 10 years.	Inverter/charger and controller: 5 years Battery: 10 years with unlimited cycles within that time as long as MyEnergi controller is in use.	Inverter: 5 years Battery: 70% storage capacity retained after 10 years, or (smaller batteries only) 5000 full cycles at 90% DOD, 5000 lifecycles, whichever comes first.	12 Years	Inverter: 5 years Battery: BYD – 60% storage capacity retained after 10 years Pylontech – 10 year ‘time value replacement’ guarantee, meaning the ‘time value’ of the batteries is replaced based on linear depreciation over 10 years.

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 2	Tesla Powerwall 3	MyEnergi libbi	GivEnergy Modular	GivEnergy All in One	Victron + BYD/Pylontech
Can the system be installed on a three phase connection?	Yes, up to three Powerwalls per phase. Note that ONLY one phase will work in a power cut.	TBC	Not recommended. But is technically possible, up to three libbi's per phase.	Not recommended. Use GivPCS-30, GivPCS-50, GivPCS-100 instead (GivEnergy’s three phase systems).	Not recommended. But is technically possible, up to three All in One's per phase.	Yes, typically up to four or five units can be installed per phase.
Will the system work in a power cut?	Only one phase can work in a power cut, even if Power walls are installed on more than one phase. Three phase loads and three phase solar PV will not work in a power cut.	TBC	N/A	N/A	N/A	Yes, any phase to which a Victron unit is installed will work in a power cut. Thee phase loads and solar PV will work if Victron units are installed on every phase.

Battery Storage Knowledge Bank

Residential Solar Storage Systems - Comparison

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