Two quotes are comparable only if they address the same need. A lower price can mean less capacity, a narrower installation scope or different assumptions. Before choosing, rebuild a common comparison instead of placing two headline prices side by side.
Put the scope on one page
Copy the exact equipment references, usable capacity, power rating and included accessories. Ask whether installation, commissioning and electrical modifications are included. Mark each item “included”, “excluded” or “to confirm”. An empty cell is not a zero.
Separate optional extras from the configuration needed to meet your objective. This shows the cost of a working installation without adding optional items to one proposal while overlooking them in the other.
Request the calculation inputs
The financial example should use your consumption, generation and contracts. If the quotes assume different electricity prices, ask for both to be recalculated with one common set of inputs. Also request annual battery throughput and the way losses are handled.
A saving without a calculation method is not a sound basis for comparison. A more conservative estimate with visible steps is more useful than a larger number that cannot be reproduced. Keep changes to the assumptions in a separate version so you can understand why the outcome moves.
Read the warranty as a set of conditions
Record the stated duration, retained-capacity threshold, operating conditions and fault-reporting process. Ask who performs repairs, who transports equipment when necessary and which charges might remain payable. Review these points with the supplier; this checklist does not replace the contract itself.
Check access to monitoring and settings as well. If an important function requires a subscription, include it in running costs and consider what happens after cancellation.
Keep a traceable decision
- The same requirement given to each supplier.
- A confirmed list of included and excluded work.
- One dated set of financial assumptions.
- Relevant warranty and maintenance documents.
- A written explanation of differences that remain.
The goal is not to turn every purchase into a complex audit. A clearly structured page often reveals the main omissions. Decide once the differences have been explained, then keep the comparison alongside the invoice and commissioning records. It becomes a useful reference when reviewing the installation’s actual performance.
This article is an editorial comparison method, not a product ranking or an assessment of any named supplier. No equipment was tested for this checklist.
Sources and transparency
Sources document the principles discussed. Examples, checklists and calculations are educational tools from BatteryIncome, not quotes or performance promises. Contract terms and offers need to be checked when you assess a project.