“Battery” describes storage, not one chemistry or one job. A domestic heat battery stores energy as heat. Sodium-ion and solid-state batteries are electrochemical technologies intended to store electrical energy.
The short answer
Choose the category by the output you need. If the end use is hot water or space heating, storing heat directly may be relevant. If the home needs electricity for sockets, lighting or backup, investigate electrical battery storage.
| Term | Stored form | Useful output |
|---|---|---|
| Heat battery | Thermal energy | Hot water or space heat |
| Sodium-ion battery | Electrochemical energy | Electricity |
| Solid-state battery | Electrochemical energy | Electricity |
Solar does not make them interchangeable
Surplus solar electricity can charge either electrical storage or, through a heating element or heat pump, thermal storage. The better route depends on the later demand, export value, conversion losses and installed cost.
Backup power is a separate requirement
A heat battery cannot normally keep lights or broadband running during a power cut. Many home electrical batteries also require specific backup equipment to operate when the grid is down.
“Battery life” means different things
Thermal stores and electrochemical cells age through different mechanisms. Compare warranted output, conditions, service route and end-of-life plan within the relevant category.
Your next step
Write the sentence “I need to store ___ so I can use ___ later.” Fill both blanks before opening a product comparison.
Sources
Primary and independent references checked by our editorial team.
- Energy storage options explained — Energy Saving Trust Checked 10 Nov 2026