Use your actual quotes
Obtain quotes for several deductible levels with all other settings unchanged. Multiply each monthly premium by twelve. The difference is your annual premium saving. Do not use a supposed nationwide fixed discount or someone else’s break-even figure: the comparison needs your own tariff.
Compare different treatment years
Estimate a low, medium and high level of eligible spending. For each, add the deductible contribution and relevant cost sharing to the annual premium. Distinguish covered treatment from services you would pay in full. Pregnancy, medicines and hospital stays may require adjustments rather than a blanket calculation.
Consider cash reserves
A high deductible can look attractive in a quiet year but requires enough available cash when treatment occurs. Ask whether you could pay several invoices promptly without borrowing. Confirm change deadlines directly with your insurer before instructing a change; reducing a deductible and increasing it need not follow identical notice arrangements.