The Tesla Powerwall 2 is one of the most advanced energy storage systems in the world, and the real magic behind it is the batteries. Tesla’s leadership in battery technology from the cell to the pack and into the finished products that utilise them highlights the fact that Tesla is truly not just an automotive company but really more of a broader tech company. 

Tesla has created a Powerwall Overview and an AC Powerwall Owner’s Manual, which provides significantly more information for people interested in looking behind the curtain.

The Powerwall 2 is an advanced DC energy storage system with a usable capacity of 13.5 kilowatt-hours per Powerwall. For more storage capacity, multiple Powerwalls can be installed in parallel. As most businesses run on AC power, Tesla stacked an inverter on top of the battery pack that turns the stored DC power from the battery into AC power that all appliances can use. The inverter can push out the resulting AC power at 7kW peak or at a 5kW continuous rate. Bundling more Powerwall 2s together in a single installation also provides the capability to support even larger power draws.

Conversely, when it comes time to charge, the inverter can turn AC power back into DC power that is stored in the battery. This inverter has a round trip efficiency of 90%, meaning that 10% of the power sent into the Powerwall to be stored is lost by the time it gets back out due to the inefficiencies of converting the power from AC to DC (going into the Powerwall) and from stored DC power back to usable AC power as it comes out of the Powerwall into the home.

Batteries are commonly rated, compared, and discussed based on their usable capacity, as listed in kilowatt-hours (kWh). Unfortunately, the world of storage capacities is not a straightforward one, with some manufacturers listing the total capacity of the battery cells in the unit even though some of it might be reserved to protect the life of the battery.

Tesla lists the capacity of its Powerwall 2 units in terms of usable capacity, which is the total amount of energy stored in the battery that can actually be used. It features a 100% depth of discharge, meaning that the entire 13.5 kWh of usable capacity can be pulled out, if needed.

Tesla Powerwall Spec


Clean solar power round-the-clock

During the day your Solar PV system charges your battery. At night you draws electricity from your battery, powering your home or business with clean, sustainable energy around the clock. Powerwall 2 can also charge from the grid, it comprises of 13.5kWh of usable storage in a lithium-ion battery pack, which can power an average 2-bed property for an entire day.

Protect your home or business from power cuts with Backup Gateway

Now available with Backup Gateway to protect your home or business from the disruption of power cuts. Backup Gateway will detect a power outage and trigger your Powerwall 2 to take over. It will also ensure your Solar PV system continues to produce energy (without it Solar PV stops working during a power cut).

Extremely cost effective

With up to 13.5kWh of storage and capable of delivering 5kW of power continuously and up to 7kW for 10 second periods, the Powerwall  is extremely good value as the price per kWh of storage is by far the lowest on the market.

Smart technology enables you to take advantage of time-of-use and export tariffs.

Sell electricity back to the grid at peak prices

Take advantage of new agile tariffs, selling power back to the grid during peak rates. Intelligent forecasting software learns when energy is most needed and helps maximise your financial benefits.

Peace of mind

iGen are a Tesla approved installer. We take care of everything from system design, DNO registration, installation and commissioning. Powerwall comes with a 10-year unlimited cycle warranty with guaranteed energy retention level when used in Self-Powered or Backup mode.

Flexible installation

The unit mounts seamlessly, indoors or outdoors, to a wall or the ground. In total 10 Powerwalls can be linked together to offer a massive 120 kWh of battery storage, ideal for larger homes or commercial application.


Powerwall economically meets the daily energy needs of most homes at one of the lowest cost per kWh.


Monitor your solar use in real-time and receive alerts when Powerwall is preparing for severe weather.

Tesla Powerwall


Powerwall is the only home battery with liquid cooling controls, maximizing battery life and safety.


Powerwall is water resistant, can be installed indoors or outdoors, and operates between –20 C to 50 C.


The new standard for commercial and utility scale battery solutions. Business consumers and energy providers can gain greater control, efficiency and reliability across the electric grid.

Tesla Powerpack

There are many benefits of installing a solar battery. The economic benefits include load shifting, where an organisation can draw battery power during times of high Triad (TNUOS) charges between 4pm and 7pm during winter rather than drawing expensive grid energy.  A company can also reduce the peak load that it may draw, in order to stay below a physical or financial threshold that may be imposed by their supplier. Large pieces of industrial machinery may have this effect. A pre-charged battery can provide this energy to smooth out the spikes, without drawing high peaks from the local network. The third benefit is to act as a store for renewable energy generated on site as the battery could be charged off free solar electricity. This energy could be sold back to the grid for a nominal sum, or retained to replace future demand.

Connecting a battery to an organisation’s electrical infrastructure is done in the same way as EvoEnergy connects a large solar PV array. We generally connect the battery to the primary distribution network and ensure that the organisation’s protection systems are up to date and will behave in a known way in the event of a problem. The batteries deliver a direct current (DC) and this is passed through an inverter to create alternating current (AC) which is suitable for general use. In addition to the battery and inverters, EvoEnergy will also install a G59 relay and cut-out to protect the site in the event of an electrical failure, in addition to a series of meters to ensure that the billing and flow of energy is understood. This generally requires significant design and customers can ask iGen to investigate old infrastructure thoroughly to give them a better understanding of the risks within their systems.

Capacity is the total amount of energy in kWh (units) that a battery is capable of storing. Batteries should never be drained completely, however  some are misleadingly sold quoting ‘total’ capacity. It is important to check what’s being stated. ‘Useable capacity’ is the key figure you need to know. For example although a Tesla Powerwall 2 is 14kWh, it’s sold as 13.5kWh, it’s useable capacity. It will not fully discharge to prevent damage to the battery cells.

There are two main types available:

  • Lead Acid
  • Lithium


Lead Acid is very cheap to install but it’s inefficient and won’t last for a longtime.  For this reason Lead Acid has all but disappeared from the Solar Storage market.  Though the price of Lithium (ion or iron phosphate) is slightly higher, it’s much better value for money.  It will last far longer and deliver more kWhs (units) during its lifetime.

A cycle is one complete discharge and one complete charge. However in reality it doesn’t happen like that. A battery may only discharge 25%, then recharge 25%. This would be a quarter of a cycle. So you need to know how many cycles a battery is warrantied for. Only then can you work out how many kWhs (units of electric) your battery will deliver over its entire warrantied lifetime.

Some battery storage systems only deliver 800w (watts) of power. No good if you want a cup of tea (your kettle needs 2000 watts).  Likewise, if you’re generating 4kW but the battery can only take on 3kW then 1kW will be heading to the grid, wasting your precious free energy.

So it’s important that you check the power output before you buy, otherwise you may find yourself drawing a lot of energy from the grid even though you have energy in your battery.

Grid services are the portion of services that are devoted to supporting the National Grid. They change from time to time as the National Grid seek to manage their network more effectively. They appear as short term markets with bidding opportunities, barriers to entry and licences. These services can be accessed from inside an occupier’s property as well as connected directly to the grid. The services typically are designed to provide additional grid stability at short notice; should an unexpected event occur on the network outside of its normal operation. By allowing your battery to be entered into these network managed markets – making your asset available to the network operator – additional revenues will be earned.

A grid connected battery is one that is connected straight to the electricity grid and derives its income solely from providing grid services to the National Grid. A “behind the meter” battery is a battery that is connected to a private electrical infrastructure, often within a factory or warehouse. In this scenario a battery can provide grid services, as a grid connected battery, and also support the occupier with load shifting, electrical storage and peak shaving services.

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