Home Battery Storage Charge and Saving Log

Who this is for

Put a figure on what your battery saves. Each day, enter the kWh charged, discharged and exported from the app, and the log values the discharged energy at your import rate, subtracts what grid charging cost and adds export income.

Households with a home battery who want a monthly figure for what it is worth on their own tariff, rather than the estimate in the app.

What this helps you track

• Daily charged, discharged and exported kWh
• What the discharged energy would have cost at your import rate
• What charging from the grid cost at your charging rate
• Export income and a net monthly figure

How to use it

1. Write the battery and month, then your import rate, export rate and the rate you pay when charging from the grid.
2. Each day, copy the charged, from-grid, discharged and exported kWh from the battery app or inverter.
3. The saving, grid charging cost and export income are worked out in the browser and the workbook.
4. Leave the from-grid column blank on days the battery charged only from solar.
5. At month end, read the net figure in the summary and start a new sheet, or a new tab online.

Formats

• Printable PDF (A4 and US Letter)
• Fillable PDF with form fields
• Fill in online, saved in your browser
• Excel / Google Sheets workbook

The printable is laid out inside a box that fits both A4 and US Letter, so the two files are identical and neither one is scaled. The fillable PDF has real form fields. The workbook uses plain formulas only — SUM, IF, COUNTIF and the like — so it opens in Excel, LibreOffice and Google Sheets without anything breaking, and every calculated cell is grey so you can see which figures it worked out.

How to print

Download the A4 or US Letter file to match the paper in your printer, open it in a PDF reader and print at 100% — not "fit to page", which shrinks the writing space. Both files leave a 14 mm margin, which clears the unprintable edge on home printers. To print the online version with your entries in it, use the Print this sheet button, which prints only the sheet and none of the page around it. More on printing.

Questions

What does the saving figure mean?

It is the discharged kWh multiplied by your import rate: what that energy would have cost from the grid. The net figure then subtracts what grid charging cost and adds export income.

Which charging rate do I enter?

The rate you pay at the times the battery charges from the grid, often a cheaper overnight rate on a time-of-use tariff. Take it from your own tariff; none is supplied.

Does it account for losses in the battery?

Only through your own figures. Charged and discharged kWh from the app already show the difference, so the net figure reflects what the battery actually delivered.

Is export from solar or from the battery?

Whatever your app reports as exported for the day. If you only want battery export, use the figure the app gives for battery export and note it in the header.