Is lithium or lead-acid safer for a home battery?
Lead-acid is the more thermally stable chemistry, and lithium-ion carries the risk of thermal runaway. Both can be installed safely when the system is designed and installed properly.
Thermal runaway is a chain reaction. A damaged or failing lithium-ion cell heats up, the heat triggers the cells next to it, and the fire feeds itself. That is why lithium-ion fires get so much attention from fire departments and code officials. Lead-acid batteries do not fail that way. RoseWater chose advanced lead-acid for its HUBs for safety, thermal stability, predictable behavior and recyclability.
| Advanced lead-acid (RoseWater HUB) | Lithium-ion (most storage batteries) | |
|---|---|---|
| Thermal behavior | Stable, no thermal runaway chain reaction | Thermal runaway is the main fire risk |
| Energy density | Lower, so larger for the same storage | Higher, so more compact |
| Usable life | 7 to 10 years, per RoseWater | Varies by product; check the warranty |
| Recyclability | More than 90%, per RoseWater | Recyclable, with collection still developing |
| Indoor permitting | Can mean less friction, per RoseWater | Subject to energy storage fire rules in many places |
| Typical use | Always-online conditioning plus backup | Solar storage and backup |
How long do home batteries last?
Home batteries last anywhere from several years to well over a decade, depending on chemistry, how hard they are cycled and the temperature they live in. RoseWater states a proven usable life of 7 to 10 years for the batteries in its HUBs.
How a battery is used matters as much as what it is made of. A battery that is drained and refilled every day for solar time-shifting works much harder than one that stays full and steps in only during sags and outages. A RoseWater HUB is built the second way. Its batteries engage during sags and outages, and rectifiers keep them charged the rest of the time. Temperature matters too. A basement or a conditioned garage is a better home for any battery than an attic or an unheated shed.
Storage can also grow with the house. Extended battery packs come in two sizes: a three-shelf pack adds 28.8 kWh and a five-shelf pack adds 40 kWh.
Can a home battery catch fire?
Any battery can fail, so the real question is how it fails and how the system is designed around that. Lithium-ion fires are the main concern with home batteries because thermal runaway can spread through a pack.
Lead-acid batteries are not without risk. They can release gas if they are overcharged, which is why charging is managed by the system and the install space has to meet the manufacturer’s requirements. What they do not do is feed a fire from cell to cell. RoseWater’s cabinets are also seismic-rated, and every installation is commissioned by RoseWater-trained technicians.
Why do some towns restrict lithium batteries indoors?
Towns restrict lithium batteries indoors mainly because of the fire risk and how hard lithium-ion fires are to extinguish. Rules come from fire and building codes, and they are applied by local officials.
Fire codes such as NFPA 855 set requirements for where energy storage systems can go, how big they can be and how they are separated from living space. Because the rules were written with lithium in mind, RoseWater notes that some towns treat any large battery as a lithium energy storage system. A lead-acid system can mean less regulatory friction, though every town decides for itself. We raise it with the building department early so there are no surprises.
If a town will not allow a battery indoors, the RoseWater HUB40 has an outdoor enclosure that is powder-coated, weather-resistant and climate-controlled. Our Cape Cod and Islands guide covers outdoor placement on coastal properties.
Are home batteries recyclable?
Home batteries are recyclable, and lead-acid has the most established recycling system of any battery type. RoseWater states that its batteries are more than 90% recyclable.
Lead-acid batteries have been collected and recycled for decades through the same channels that handle car batteries. Lithium-ion batteries can be recycled as well, and the industry is building more capacity for it, but the system is younger. For an owner who cares about what happens at the end of the battery’s life, this is worth asking about whichever product you choose.
What RoseWater does differently
RoseWater chose its battery chemistry to suit the job the HUB does. A HUB is always online with double conversion, so its batteries stay ready and step in during sags and outages with zero transfer time. The same system conditions power, regulates voltage, filters noise and absorbs surges and lightning rated up to 40 strikes of 140,000 V.
Every HUB20 and HUB40 starts with 28.8 kWh of storage. The HUB20 expands to 86.4 kWh and the HUB40 to 172 kWh. 3-Phase systems have batteries sized to the project. The trade-off is space. Lead-acid is larger than lithium for the same storage, so a HUB needs a spot about 3.5 feet wide, 3 feet deep and 8 feet high, plus 36 inches clear in front. It does not need air conditioning indoors.
Choosing for your home
Start with what you want the battery to do. If the goal is protecting a technology-rich home every day as well as in outages, our Power Plan tool is the place to begin. We size the system, plan the space with your builder or electrician, and work through local rules before anything is ordered. You can also ask us about your town.
