What you get
Two files, downloaded the moment payment clears. No account, no login, no email gate.
The Solar Savings Ledger
Our payback calculator tells you what a kit should do. This is the book you keep to find out what it did — daily generation, monthly savings, export income, and payback-to-date measured against what you actually paid. After twelve months you stop estimating and start knowing.
XLSX
solar-savings-ledger.xlsx
A six-sheet Excel workbook with the arithmetic already wired in. Opens in Excel, LibreOffice, Numbers and Google Sheets. Enter the daily kWh and the Summary sheet does the rest.
PDF
solar-savings-ledger-print.pdf
An 18-page printable A4 logbook — cover sheet, how-to page, twelve monthly generation sheets, and the savings, export, payback and maintenance ledgers. For the pen-and-clipboard-by-the-consumer-unit approach, which is the one people actually keep up.
The six sheets
01
Generation Log
One row per day for a full year. Date, daily kWh, weather and notes. The weather column is not decoration — it is how you tell a dull fortnight from a failing panel six months later.
02
Savings Tracker
Twenty-four months of grid kWh imported against solar kWh used at home, at your own unit rate. The bill saving column works itself out.
03
Export Log
Twenty-four months of exported kWh at your Smart Export Guarantee rate, with a column for the supplier statement reference so you can prove what you were paid.
04
Payback Ledger
Running total saved against what the kit cost, and the percentage of payback reached, with a data bar so you can see the line move. Every row carries the gov.uk £70–£110 a year band alongside your own figure.
05
Maintenance Log
Cleaning, inspections, faults, warranty registration and your G98 notification reference. Pre-seeded with the five entries worth making at least once.
06
Summary
Enter your kit price and tariffs once. Total generation, savings banked, export income, still-to-repay, payback percentage, run-rate annual saving and estimated years remaining, all calculated from the logs.
Why keep a ledger at all
Because the published figures are averages, and you are not an average. gov.uk estimates £70–£110 a year for an 800W system, and that is a perfectly honest national range — but your balcony faces a particular direction, your neighbour's tree throws a particular shadow, and your household is either home in daylight or it is not. Those three things move the result more than the kit you bought.
A ledger settles arguments. It tells you whether the panels need cleaning or whether it was simply a dull March. It tells you, at month eighteen, whether the thing has paid for itself or whether you were sold an optimistic number. And if you ever need to make a warranty claim, it is a dated record rather than a recollection.
What this is not
It is not software, not a subscription, and not connected to your inverter. It will not pull readings automatically — you type them in, which is the point: the fifteen seconds a day is what makes you notice when something changes.
It is also not a forecast. The workbook models nothing. It records what happened and does the arithmetic on it. If you want the projection, the calculator is free and always will be.
Honest small print
This is a digital download, so under the Consumer Contracts Regulations the fourteen-day cancellation right ends once the download begins — which is immediately, since Stripe sends you straight to the file. If the workbook does not open, or it is not what the page above described, email us and we will refund you. See the terms for the full position.