Before You Buy More Microsoft 365 Storage, Reclaim What You Already Have

There’s a pattern we see often.

The Microsoft 365 storage warning lands in the admin’s inbox — the tenant is at 95% of its included pool.

The renewal manager flags it on the next review.

Procurement is asked to approve additional storage.

The line item gets added; the bill goes up; the tenant uses the new headroom for six months; the cycle repeats. 

The conversation rarely includes the alternative: don’t buy more. Reclaim what’s there. 

Why “buy more” is the default 

Three reasons. First, buying more storage is operationally cheap — a button in the admin centre, no project plan, no change management. Reclaiming is a project. 

Someone has to own it. 

Second, the value of reclaimed storage is invisible — there’s no line item that says “this TB was almost wasted, but we didn’t waste it.”

The savings show up as the absence of a bill increase, which doesn’t get press releases.

Third, most teams don’t have visibility into what’s reclaimable. Without an inventory, every site looks load-bearing. 

The actual cost of “buy more” 

Microsoft’s list price for extra SharePoint storage is $0.20 per GB per month, or $200 per TB per month. That’s $2,400 per TB per year — and it recurs, indefinitely.

A 5 TB top-up authorised today is $12,000 a year next year, $12,000 the year after, and so on, until someone re-examines it. Few teams ever do. 

The actual cost of reclaiming 

A well-scoped storage cleanup project on a 1,000-seat tenant takes about 60 hours of staff time spread across IT and a handful of department leads. Tooling cost — TSO or equivalent — is roughly 10–20% of the first-year savings.

The cleanup itself doesn’t require purchasing additional Microsoft services; almost everything you need (retention policies, archive, version controls) is included in the plans you already pay for. 

Where the numbers cross over 

We modelled this for three company sizes: 

For tenants below 100 users at modest storage levels, the included pool absorbs everything and the math doesn’t work.

From mid-market upward, the recurring savings outpace the cleanup cost in the first quarter. 

Why this happens twice 

Once a tenant has been cleaned up, the same drivers that grew it the first time start again — recordings, version history, orphans, duplicates, media-in-the-wrong-place.

Our data on engagements past six months suggests a half-life of about 18 months between cleanups. 

That’s still three quarters of clean billing between projects. Compounding, it’s the cheapest infrastructure decision most M365 admins ever make. 

What to do this week 

If you’re approaching your included pool — within 80% — run a scan.

If you’re already over the line and paying monthly, run two scans: one now, one ninety days after you act on the first set of recommendations.

Watch the bill move.

Decide whether the next conversation with procurement is about buying more storage or buying less.