Compare solar payback and additional battery return
The starting values are an illustrative example, not current tariffs, a roof prediction or an installation offer. Replace them with your annual statement and surveyed quote. Generation means annual AC energy available to the home.
Your annual estimate
What changes the solar result?
These one-at-a-time scenarios vary direct use by ten percentage points, then each unit rate by 20%. Cautious, central and optimistic refer to the resulting annual benefit at the entered rates, not forecasts. More direct use improves value only when avoided imports are worth more than exports.
Horizon cash flow table
This constant-year projection uses a fixed 20-year display horizon for solar alone, or your selected battery horizon when comparing storage. It includes the purchase at year zero, repeats the entered annual benefit and operating costs, and assumes 0% tariff escalation, 0% degradation and no replacement. It is a scenario, not lifetime return or a discounted forecast. Actual equipment loss or replacement can worsen it.
Inputs and provenance
Model solar-ac-1.0.0; assumption set illustrative-2026-11-01. User-edited scenario inputs are estimates unless supported by your own measured data or quote. Read the equations, source register and limitations.
Non-contact inputs are carried only within this browser session where storage is available.
What simple payback measures
The tool divides purchase cost by first-year annual benefit after the additional annual operating costs entered. It does not include finance, discounted cash flow, changes in tariffs, roof-specific generation, degradation or replacements. A separate constant-year cash-flow table starts with the purchase at year zero.
Direct use is bounded by generation and household demand. You choose its share because annual totals do not establish timing. Import and export pence convert to pounds once in the shared model; each kWh is credited only once.
Read battery return separately
The battery shifts explicitly assumed otherwise-exported solar, loses some energy and reduces later grid imports. Its incremental benefit subtracts forgone metered exports. It does not automatically increase direct use or add an arbitrage bonus. Legacy deemed/unknown payment cases need agreement details before a financial verdict.
A theoretical payback longer than the selected horizon is shown alongside no cost recovery within that horizon. Combined system payback is a different result and cannot establish the battery’s own return. Existing owners should start with the retrofit checks.
Use your quote and keep the assumptions
Get annual AC generation from the surveyed design; this version does not use unsupported roof, postcode or region adjustments. Enter the solar-only cash total and additional battery cost separately. Check an existing quote before treating its claims as measured evidence.
Print the inputs and results to retain the version used. Session handoff contains non-contact numeric inputs only; no public result URL is created. Read the full methodology and source register.
Worked scenarios from the shared model
Synthetic examples, not measured installations or current offers. Each assumes 3,600 kWh generation, 4,000 kWh household demand, GBP 6,000 solar cost, 30p import, 15p metered export and zero additional annual operating cost. Direct-use shares vary. No tariff escalation, degradation or replacement is included.
| Scenario | Annual total benefit | Solar / combined simple payback | Additional battery payback |
|---|---|---|---|
| Lower daytime use | GBP 648.00 | 9.3 years | No battery |
| Central solar only | GBP 756.00 | 7.9 years | No battery |
| Higher daytime use | GBP 864.00 | 6.9 years | No battery |
| Central with additional battery | GBP 876.00 | 10.3 years | 25.0 years |
The battery example diverts 1,000 kWh from exports, delivers 900 kWh after 100 kWh losses and costs an additional GBP 3,000. The battery adds GBP 120/year and does not recover its cost within the selected 10-year horizon. High export prices can reduce or reverse this benefit. See equations and limits.
Sources and review dates
Research-based guidance. Source checks do not imply product testing or verification of an individual installer.
- Energy Saving Trust: Solar panels. Solar suitability, generation, roof and installation considerations; not a local quote dataset. Scope: UK. Checked .
- Energy Saving Trust: Battery storage. Storage losses, scope of cost estimates and possibility that savings do not justify battery cost. Scope: UK. Checked .
- Ofgem: Smart Export Guarantee. Eligibility and supplier-set export terms; export payments are not installation grants. Scope: Great Britain. Checked .
- Ofgem: FIT generators. Existing FIT arrangements require agreement-specific checks before storage or export changes. Scope: Great Britain. Checked .
Registry sources-2026-11-01. Tariffs have a 30-day internal review interval. Methodology and assumptions.