Savings come from shifting electricity purchases into cheaper periods, not from generating energy.
The Short Answer
A battery-only system can reduce electricity costs, but the annual saving depends on the tariff spread, battery capacity, efficiency, cycles per year and how much expensive electricity it displaces.
A simple savings model
Estimate the usable kWh delivered per cycle, multiply by the difference between the avoided rate and the effective stored-energy cost, then multiply by realistic cycles per year.
Do not use nominal capacity blindly
Allow for depth of discharge, backup reserve and conversion losses. Savings models based on the battery nameplate alone usually overstate the result.
Household load is the ceiling
A larger battery does not automatically create more savings. If the home does not use enough electricity during the expensive period, some stored energy will remain unused.
Payback is tariff-sensitive
A tariff change can materially alter payback. Re-run the model when your supplier, rates or charging windows change.
Key Takeaway
Battery economics depend on the complete energy flow: what electricity costs when you charge, what it would cost when you discharge, what solar export is worth, and how efficiently the battery is used.
Frequently Asked Questions
Can I save every day of the year?
Potentially, but actual cycling depends on demand, tariff structure and how the battery is controlled.
Does a bigger battery always save more?
No. Capacity beyond your usable daily load can have low incremental value.
Should I include battery degradation?
For a detailed investment model, yes. A simple first-pass estimate can be conservative on usable capacity and cycling instead.
Estimate My Battery Savings
Use your actual smart-meter consumption and tariff rather than a generic household average.
Tariffs, supplier terms and export payments change. Check the current plan details before making a purchasing or settings decision.