Choosing a higher excess reduces the premium on almost any policy. The saving comes from two distinct effects, and only one of them concerns the money the insurer no longer pays.
Small claims are disproportionately expensive to handle
Every claim carries administrative cost regardless of size: assessment, correspondence, adjuster time and payment processing.
On a small claim, that cost can approach or exceed the amount paid out, so the insurer's total expense is far more than the loss itself.
An excess removes those claims from the system entirely, and the saving reflects both the payments avoided and the handling costs eliminated.
Claim frequency falls faster than severity
Loss distributions contain many small events and few large ones. Raising the excess removes a large share of claims by number while removing little of the total value.
Beyond a certain point, further increases save less because the remaining claims are large ones the excess barely touches.
This is why premium reductions diminish as the excess rises, and very high excesses often deliver disappointing savings.
The policyholder gains a stake in the outcome
Insurance can reduce a policyholder's incentive to avoid loss, since the consequence has been transferred to someone else.
An excess restores part of that incentive by ensuring any claim carries a personal cost, which affects both prevention and the decision to claim at all.
Insurers price this effect because it changes actual loss experience, not merely who pays for it.
Excess structures differ in how they apply
Some policies apply the excess per claim, others per policy period, and some apply separate amounts to specific perils such as storm or subsidence.
Compulsory excesses set by the insurer sit alongside voluntary amounts chosen by the policyholder, and the two add together.
Comparing premiums without comparing these structures produces misleading results, since the cheaper policy may simply be transferring more of the loss.
The right level depends on capacity to absorb it
An excess is only a saving if the amount could be paid comfortably at the moment a claim arises, which is often a moment of other financial pressure.
Setting it above what could be found readily converts an insured risk back into an uninsured one for the range it covers.
Because policy wordings and excess structures vary considerably, the terms of the specific contract determine what is actually being bought.