Duplicati on Backblaze B2 vs Backblaze Personal Backup: where the yearly cost actually crosses over

Duplicati backing up to Backblaze B2 costs less per year than a Backblaze Personal Backup subscription only below a dataset size you can calculate in one line, and that line is the whole decision. Personal Backup charges a flat annual fee per computer for unlimited data, so its cost curve is horizontal. B2 charges per gigabyte stored per month plus API calls and egress above the free allowance, so the Duplicati bill starts near zero and rises in a straight line. Divide the annual subscription fee by twelve times the B2 per gigabyte monthly rate, and you get the crossover in gigabytes: below it Duplicati wins every year, above it the subscription wins and keeps winning harder as you add data. TL;DR - The 400 GB laptop owner, one MacBook holding documents, photos and a code folder: run Duplicati to B2, because a few hundred gigabytes billed per gigabyte per month sits far under any flat annual fee, and Duplicati compresses and deduplicates before you are billed. - The 6 TB media keeper with a film and music library on external drives: stay on Personal Backup, because unlimited flat pricing per computer is unbeatable at that volume and B2 charges for every terabyte forever. - The two person household with three laptops totalling 1.5 TB: run Duplicati into one B2 bucket, because the subscription is licensed per computer while a single bucket and three Duplicati jobs cover all of them under one bill. - The homelab operator with a NAS, a Proxmox host and two Linux VMs: Duplicati is the only option of the two, because Personal Backup is a Windows and macOS desktop product that excludes network shares and server operating systems. - The person who has never restored a file and wants zero maintenance: stay subscribed, because Duplicati's real price includes your own hours on local database rebuilds, retention tuning, verification runs and failure monitoring. - The person restoring large amounts often, for example a video editor pulling back 500 GB projects: model the egress before you switch, because Personal Backup restores are included while B2 bills downloads once you pass the free egress allowance. The central tradeoff is a flat fee that ignores how much data you own against a metered bill that rewards you for owning less of it, with the difference paid in your own attention. Table of contents - What does Duplicati plus Backblaze B2 actually cost you per year? - What does a Backblaze Personal Backup subscription actually cost per year? - At what dataset size do the two cost curves cross? - Deduplication, compression and the number B2 really bills you for - How much do restores cost, and how often will you actually restore? - How does retention depth change the arithmetic? - Tuning Duplicati remote volume size, upload threads and API call classes - Multiple computers, NAS shares and the per computer licence - What each product simply refuses to back up - Where should you run Duplicati, and what does the host add to the bill? What does Duplicati plus Backblaze B2 actually cost you per year? Duplicati itself is free and open source, so every euro or dollar on your annual bill comes from B2 and from your own hardware. The bill has four moving parts, and only one of them is the obvious one. - Storage per gigabyte per month: B2 bills the average bytes stored across the month, so your annual cost is roughly your stored size multiplied by the published per gigabyte rate multiplied by twelve. This is the dominant term for almost everyone. - Stored size, not source size: Duplicati 2 deduplicates at a default block size of 100 KB and compresses before upload, so a 500 GB source folder rarely becomes 500 GB in the bucket. Documents and code shrink hard, video and photos barely move. - Transaction calls: B2 splits API calls into Class A, Class B and Class C, with Class A calls such as uploads free and the listing and download classes billed per thousand calls. Duplicati's default remote volume size of 50 MB means a 500 GB backup lands as roughly 10,000 objects, which keeps call counts modest but not zero. - Egress on restore: B2 includes a free download allowance tied to your average stored data, and bills per gigabyte beyond it. Routine backups download nothing, so this term is zero in most years and spikes only when you restore. - Version retention: every kept version of a changed file is extra stored bytes, billed monthly like everything else. Add those four, and you have a number that scales with what you actually own. What does a Backblaze Personal Backup subscription actually cost per year? Personal Backup is a flat fee per computer, billed monthly, yearly or on a two year term, with the longer terms carrying a lower effective annual rate. Unlimited means unlimited: 200 GB and 20 TB on the same machine cost the same. The complications are not in the headline price. - The licence covers one computer, not one household: three laptops means three subscriptions, and the annual cost triples while the amount of data protected is irrelevant to the bill. - Version history defaults to 30 days: deleted or changed files fall out of the backup after 30 days unless you pay for an extended version history add on, sold as a one year option and a forever option. - Forever version history is not flat: the forever tier adds a per gigabyte per month charge for data older than one year, which reintroduces exactly the metered pricing model you left B2 to avoid. - External drives count, network drives do not: USB attached disks are included at no extra cost, but a NAS share, a mapped network drive or a Linux server cannot be backed up at all, so protecting them means a second product on top. - Attached drives must be reconnected every 30 days: disconnect an external disk for longer and its backed up data is purged from the account, which is a silent cost if you rotate archive drives. - Restores are included: web download and restore by mail both come with the plan, with the mailed drive refunded on return. The predictable number on the invoice is the product's main feature. At what dataset size do the two cost curves cross? Work it out yourself in one line. Take the annual Personal Backup fee, divide it by twelve, then divide that by the current B2 per gigabyte monthly rate. The result is the crossover in gigabytes stored, and both numbers are published on Backblaze's own pricing pages, so the calculation stays correct as rates change. Call that crossover point C. | Bytes stored in B2 | Duplicati annual cost versus one subscription | What it means for you | |---|---|---| | 0.25 x C | About 25 percent | Duplicati is clearly cheaper, and the gap is large enough to absorb restores | | 0.5 x C | About 50 percent | Duplicati is cheaper, with room for retention growth before parity | | 1 x C | Parity | Choose on features, not on price, because the invoices match | | 2 x C | About 200 percent | The subscription is cheaper and the gap widens every month you add data | | 4 x C | About 400 percent | Only non cost reasons justify Duplicati at this volume | Two adjustments move C in your favour. First, C scales linearly with the number of machines: three computers on Personal Backup means three fees, so your effective crossover is 3 x C for a single B2 bucket holding all three. Second, C applies to stored bytes, not source bytes, so Duplicati compression can put a 700 GB source folder comfortably under a 500 GB crossover. One adjustment moves it against you: unlimited retention on B2 grows stored bytes forever, while the flat fee never notices. Deduplication, compression and the number B2 really bills you for Your source folder size is not your invoice. Duplicati hashes every block with SHA-256, stores each unique block once, packs blocks into archive volumes and compresses them before upload. Four things decide how far that gets you. - File type dominates the ratio: text, code, spreadsheets, mailboxes and virtual disk images compress and deduplicate heavily. JPEG, MP4, MP3 and existing ZIP archives are already compressed, so expect close to no reduction. Duplicati ships a default_compressed_extensions.txt list and skips compressing those types rather than burning CPU for nothing. - Deduplication is per backup job, not per bucket: two jobs covering the same 40 GB photo folder store those blocks twice and you pay twice. Consolidating overlapping folders into one job is free money. - Deleted data stays billable until compaction runs: when retention removes an old version, its blocks remain inside archive volumes that still contain live blocks. Duplicati only rewrites a volume once wasted space passes the compact threshold, 25 percent by default, so stored bytes lag behind logical deletions. - Encryption adds a small constant, not a percentage: AES-256 output is roughly the size of its compressed input plus per volume header overhead, so encryption costs you almost nothing on the bill. - The dashboard tells you the truth: the job's reported backend size, not the source size, is the number to feed into the crossover calculation from the previous section. Measure once with a real backup before committing. A 1 TB documents heavy dataset and a 1 TB video library produce completely different B2 bills. How much do restores cost, and how often will you actually restore? Most people restore a handful of files a year and a full dataset once a decade, if ever. That matters because B2 includes a free download allowance of three times your average monthly stored data, so a household sized restore usually lands inside it. - A single full restore is normally free: pulling back everything you store is 1x your stored bytes against a 3x allowance, so you would need to restore your entire backup three times in one month before egress charges start. - Small restores cost more than you expect in bytes: Duplicati downloads whole archive volumes, so recovering one 2 MB document can pull a 50 MB volume. The cash impact is negligible, the wait is not. - Restoring without the local