PRTG Free Edition 100 Sensors What They Really Cover in a Small Office
"Only 100 free sensors" sounds like a demo. Planned like a budget instead of spent like confetti, it is a complete monitoring system for a real small office - here is the shopping list.
By Technical AnshuPaessler PRTGWindows Server and Network
Watch the complete PRTG setup in the video - CPU, RAM, bandwidth and firewall monitoring, step by step
Paessler's freeware edition is not a trial and not a crippled demo: it is 100 sensors, free for life, with the same alerting, reporting and mapping features as paid editions. The catch is purely arithmetic - one sensor is one measured value, and a device typically wants 5 to 10 of them. So the real question is not whether 100 is enough, but enough for what shape of office. Let us spend the 100 on paper.
Spending 100 free sensors on a 25-person office (example plan)
3 servers x 7 sensors ....... 21
Firewall (4) + core switch .. 8
2 access switches, uplinks . 4
NAS - ping + 4 disks ........ 5
Internet line + website ..... 4
5 printers x 2 .............. 10
UPS + temperature ........... 3
--------------------------------
TOTAL ........................ 55 of 100
Headroom for growth ......... 45
Example plan, not a quote - your office will spend differently, the method is the point
1
What the Free Edition Actually Includes
Everything except scale. The freeware sensors, notifications, reports, maps and the mobile app are the real product - Paessler's model is that small networks are genuinely served, and growing networks buy sensor packs in steps. The first 30 days after installation run unlimited, which is a trap and a gift: a gift because discovery can show you everything, a trap because day 31 asks you to choose your favourite 100.
2
Spend on Servers First, Network Second, Rest Barely
The plan above follows one rule: depth where failure hurts, shallowness where it does not. Servers get CPU, memory, every disk, key services. The firewall gets its three layers. Switches get uplinks only, never all 24 ports. Printers get ping plus one supply sensor. Ordinary PCs get nothing - monitoring user desktops in depth is how budgets die and privacy arguments are born.
3
The Habits That Waste the Free 100
Letting auto discovery keep everything it creates
Graphing every switch port "for completeness"
Duplicating a check two ways (WMI disk and SNMP disk) out of indecision
Monitoring test VMs and the box under your desk with production depth
Never deleting sensors for devices that left the building months ago
4
When You Honestly Outgrow It
You will know: a second site arrives, or the switch-port question becomes real, or compliance asks for checks you cannot fit. Then the upgrade is calm, because a year of sensor history tells you exactly how many you need - buy the step that fits the audited list, not the fear. Outgrowing a free tool with data in hand is the cheapest software purchase in IT.
Honest note: 100 sensors will not cover a 200-seat company, a rack of hosts, or a campus - and pretending otherwise by deleting alerts is worse than paying. The free edition's true promise is narrower and real: one site, a handful of servers, core network gear, fully watched.
Watch the Complete PRTG Setup in the Video
Every sensor in this guide is created live in the video - installation, discovery, CPU and RAM, bandwidth and firewall status.
Does the free edition expire after the 30-day trial?
No. The unlimited trial ends after 30 days, and then the installation continues as the freeware edition with 100 sensors for life. You pick which 100 sensors stay active; nothing about the core product is switched off.
Are notifications and reports included in the free edition?
Yes - Paessler includes alerting, reporting and network mapping features in the freeware edition. The limit is the sensor count, not the feature set.
Can I start free and upgrade later without rebuilding?
Yes. A paid licence simply raises the sensor ceiling on the same installation - your devices, sensors, history and alerts carry on. That continuity is a large part of why starting free is a rational plan, not a compromise.
This guide is based on the PRTG monitoring video by Technical Anshu - stuck on any step, ask in the video comments and you will get an answer.