Free preventive maintenance software exists, several of the products are genuinely usable, and the limits are consistent enough to plan around. What matters is knowing which limit you will hit first, because the answer decides whether free is a starting point or a dead end for your site. There is also a second kind of free worth separating out: free planning tools that compute on a page without an account, which are not software you run a site on but are the cheapest way to work out what the plan should be.
The three limits, in the order sites hit them
Asset count comes first for anybody with real plant: a free tier capped at a few dozen assets covers a small building and nothing larger. Users comes second, usually at one or two, which is fine until a second person needs to complete a visit. And features come third, most often the ones that make the plan durable: history, export, and attaching a checklist to a visit.
The limit that is not on the pricing page
What happens to your data if you stay free and then stop. Before you put a year of visit history into anything free, find the export and use it once. A free tier with no export is not free, it is a deposit, and the cost is paid at the worst possible moment, which is when you have decided to move.
Free planning tools are a different thing, and useful
A worksheet that costs a maintenance plan from your own unit count, visit length and rate is not software you run a site on. It is how you find out whether the plan you are proposing is affordable before anybody buys anything. Those should genuinely need no account, no email and no trial clock, and if one asks for your details before showing an answer it is a lead form wearing a calculator's clothes.
Questions people ask about free preventive maintenance software
Is free preventive maintenance software safe to rely on?
For a small asset list, often yes. Treat the export as the safety net: as long as you can get your assets, intervals and history out in an ordinary format, the risk of relying on a free tier is bounded.
What is the catch with free tiers?
Usually none in the short term. The economics are that a proportion of free sites grow into paying ones, so the limits are set where growth hurts: users and assets, rather than the core planning.
Can a spreadsheet do this for free?
It can hold assets and dates. What it cannot do is derive the next due date when a visit completes, which is the one behaviour that stops a plan going stale, so a spreadsheet needs a person to be the mechanism.