Start with the problem the battery is meant to solve
A battery may be considered to use more solar electricity later, reduce grid imports at expensive times, support a particular tariff strategy, prepare for future electric loads, or provide limited backup where designed for that purpose. Each objective changes the assessment.
What makes the case stronger
- Regular surplus solar generation.
- Electricity usage after solar generation drops.
- A time-of-use tariff with meaningful price difference, where suitable.
- Future EV, heat pump or higher electrical demand.
- A battery size matched to actual usage, not oversized for appearance.
What weakens the case
- Limited solar surplus.
- Very low evening electricity use.
- Flat tariffs with little price difference.
- Optimistic assumptions about daily cycling.
- Backup expectations that the design does not support.
- Short ownership horizon or uncertain property plans.
What should be modelled
A sensible appraisal should model the base solar system first and then show what the battery changes. That helps separate the value of the panels from the additional value of storage.
- Extra self-consumption expected.
- Grid charging assumptions, if any.
- Export income forgone by storing instead of exporting.
- Battery cost, warranty, usable capacity and degradation assumptions.
Questions to ask before deciding
- What is the battery expected to achieve?
- How often is it expected to charge and discharge?
- What happens in winter when solar generation is lower?
- What happens if tariff terms change?
Information and source control
Information correct as of: 17 July 2026
Sources available on request or reviewed during consultation.
