Estimate annual solar savings
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.
Savings and income are different
Direct solar use avoids buying electricity at the entered import rate. Otherwise-exported solar earns the entered export rate only where metered exports are paid under the applicable agreement. Standing charges remain payable and are not included as avoided cost.
The example uses 3,600 kWh generation, 4,000 kWh demand, 40% direct use and illustrative import/export rates of 30p/15p. It gives GBP 432 annual bill reduction plus GBP 324 export receipts, before additional annual costs. These are the same figures as the detailed tool for the same inputs.
Replacing an estimated bill with measured use
If estimating from a monthly bill, the tool deducts 365 daily standing charges from 12 monthly electricity bills, then divides the remainder by the import unit price. Gas, arrears, credits and other charges must be excluded. This is an approximation where bills or rates vary.
Check the implied annual kWh against an annual statement and replace it when available. Use the installer’s generation estimate and an explicit direct-use share rather than invented occupancy or roof-direction factors.
Take the estimate to detailed payback
The installed price matters to cost recovery but does not create bill savings. Enter a cost if known and open detailed payback with the same session inputs. Battery storage uses the same additional-return calculation in both tools.
If you have a proposal, check its scope and arithmetic. No enquiry or newsletter subscription is needed for a result or printout.
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 .
Registry sources-2026-11-01. Tariffs have a 30-day internal review interval. Methodology and assumptions.