Editorial method
How our calculator estimates are made
TrimMyBills tools provide planning estimates, not exact bills or regulated advice. This page explains how the numbers and review dates are handled.
Formulas
Calculator arithmetic is kept in reusable pure functions where possible. The worked example and interactive result should use the same function so the two cannot quietly disagree.
Dated sources
Time-sensitive defaults name the source, access date and effective period. Energy defaults use published Ofgem price-cap tables; users can replace the default with their own tariff.
Assumptions and exclusions
Pages explain material assumptions and what the estimate leaves out. Appliance usage calculations exclude standing charge because using one appliance does not create an additional daily standing charge.
Review and updates
A Last reviewed date changes only after the calculator, source and visible explanation have been checked. Older content keeps its earlier date until a substantive review is completed.
Corrections
If you find an outdated source, unclear assumption or reproducible calculation error, send the page URL and the issue through our contact page. We will check the source and update the page when a correction is needed.