Hi Sweta,
Your initiative is highly appreciable. congrats!!!
Appraisal software can be costly and it can vary based on the complexities in process, levels in appraisal, number of appraisals per year, type of appraisal (Eg:- Self Appraisal - Appraisal - Review pattern, Goal setting and review, 360 feedback), data to be captured in appraisal form, rating logic, fitment/normalization, reports etc.
It has been observed that no two companies would be following the same process.
So my recommendation is prepare a complete business process document with process flow, form parameters, reports required, business logic etc and share with the vendors interested to supply software.
Please avoid asking cost, upfront. This may make some of the vendors to come up with some 'figure' to bag the order and later will fail in delivering the software. Because, end of the day, business should make profit.
Also if there is no HRMS in place, before getting in to performance management software, get HRMS organized. Otherwise it can be very difficult to ensure the accuracy of basic employee data, reporting relationship etc.
For any successful implementation of Performance Management software, 3 months to 6 months is required, if requirements are completely matching with a ready to use product. Otherwise, time required to understand and develop customization can be extra
As appraisal process is one of the most sensitive process in any organization, you may need to take extra care, when you launch the software. Ensure that employees and managers are properly trained to use the software and aware of best practices.
best of luck