Lithium has owned home energy storage for about fifteen years. Everything Electric TECH visited two British houses to find out whether sodium can take a piece of it. Both are running sodium-ion packs from Eleven Energy, a UK startup, in a new stackable format that sits against a wall and grows one module at a time. The pitch is not energy density, which sodium loses on and will keep losing on. It is durability and cold tolerance. The channel reports the company put 13,000 charge and discharge cycles through test packs over roughly eighteen months, the equivalent of a full cycle every day for 35 years, after which the cells retained 85 percent of their original capacity.
Sodium sits at number 11 on the periodic table against lithium at three, so a sodium cell is bigger and heavier for the same stored energy. In a phone or a car that is disqualifying. Bolted to a garage wall it is close to irrelevant, and the video puts the penalty at roughly 15 to 20 percent more volume and weight than an equivalent lithium pack. Two things the video does not press on are worth flagging. The cycle figures come from the manufacturer's own testing rather than an independent lab, and the same installer says he could not find comparable published data for lithium packs anywhere, which makes the comparison hard to run in either direction. Space also matters more than the percentage implies. A fifth more volume is nothing in a garage and can be decisive in a flat or a tight utility cupboard.
The rest of the episode is about using a battery well rather than which chemistry is inside it. One homeowner, who designs solar systems for a living, has 29 panels on a bungalow with more than half of them facing north, and says north-facing panels still return around 70 percent of what south-facing ones would at that roof pitch. His grid connection caps export at 4.4 kW despite roughly 12 kW of panels, so he starts discharging the battery to the grid at six in the morning to flatten and lengthen the export curve, buying overnight at about 8p and selling in daylight at about 12p. Eleven Energy now offers 8, 10 and 12 kW inverters, up from 6 kW, and the channel reports its app carries an optimise toggle that pulls a weather forecast, tariff timings and past consumption to schedule everything automatically. A second household reports net import costs of around 11p since installation.
Cold weather is the other argument for the chemistry, and it is a practical one. The channel reports that many lithium home batteries carry built-in heaters, so in mid-winter a share of the energy going into the pack is spent keeping the pack warm rather than doing anything useful. Eleven Energy's cells are described as tolerating lower temperatures without that, which is why the modules are rated for outbuildings, garages and outdoor walls as well as indoor spaces. The control side has had attention too. The company says it can fit a sensor on the EV charger supply so the house battery stops discharging while the car is charging overnight on a cheap rate, and can divert surplus generation into an immersion heater instead of losing it to an export cap. Closer integration with heat pumps is flagged as the next step rather than something available now.
Bottom line: The chemistry is the least interesting part of this story. Sodium currently prices about level with lithium and takes up slightly more room, so nobody is switching for the spec sheet. They are switching because the supply chain is cleaner and the cycle life claim is enormous. If that 13,000 cycle figure holds up under independent testing, it changes how these systems should be financed, because a battery that outlives the mortgage is an asset rather than a consumable. Until somebody outside the company verifies it, treat it as promising rather than proven, and buy on the warranty rather than the graph.
Commentary on a third-party video. Figures and claims are as presented in the source and have not been independently verified. Spotted an error? Tell us and we will correct it.