01
Hardware is the visible part, not the biggest risk
PLCs, I/O modules, drives, HMIs and panel components are the easiest part of a quote to compare, because they have list prices. The brand chosen matters: many plants standardise on one platform so their maintenance team carries one set of spares and skills, and staying on that platform is often worth more than a small hardware saving.
The count of input and output points is the main driver of hardware cost and panel size. A clear I/O list at the start makes every quote comparable.
02
Engineering hours are where quotes really differ
Writing PLC logic, building HMI and SCADA screens, designing the panel and drawing the schematics take engineering time, and that time varies more between vendors than any hardware price. A low quote often means fewer hours, which means less testing, thinner documentation or logic copied from an older project.
Ask what testing is included. A factory acceptance test, where the program is proven against a simulation before reaching site, costs time up front and saves much more during commissioning.
03
Software licences and the long-term cost
SCADA and HMI software is often licensed by tag count, screens or clients, and some platforms charge annual fees. A system that looks cheap at fifty tags can become expensive at five thousand. Ask for the licence price at the size you expect to reach, not just the size you start with.
Ask too who owns the source code and project files afterwards. If changes can only be made by the original vendor, every future modification carries their price.
04
What a complete quote should include
A complete scope covers the I/O list and hardware, panel design and build, PLC and HMI or SCADA programming, factory acceptance testing, installation and site commissioning, operator and maintenance training, as-built drawings and commented source code, and a defined warranty and support period.
Items missing from one quote and present in another explain most price differences. Lining them up side by side, before negotiating price, is the single most useful step a buyer can take.
Written by the ASKworX engineering team