PCC David Jamieson said it would cost West Midlands Police about £500,000 a time when the Tories meet in Birmingham in October and return in 2018 and 2020,
He has written to Home Secretary Amber Rudd to ask for a discussion about a "fairer arrangement".
The Home Office said the funding had been reviewed as "fairer" than before.
A government grant will pay for policing of the events, a spokesman said.
Previously forces were reimbursed 85% of the operational costs plus planning costs, he added.
"This was deemed a fairer way of compensating police forces who should plan for a political party conference in the same way that they plan for other large-scale events for which they do not receive additional funding," a spokesman added.
In his letter to the home secretary, Mr Jamieson said: "It must be highlighted that making these events as safe as possible requires meticulous, extensive planning by West Midlands Police.
"It is therefore troubling that the dedicated planning team, who began work for this year's conference last autumn, is costing approximately £460,000, which will not be recouped.
"Significantly, in 2014 when Birmingham last hosted the conference, the cost of this planning team reached £520,000.
"The next four years could cost the force £1.5m if this issue is not resolved."
Birmingham's International Convention Centre played host to the conference for the fourth time in September 2014.
At its peak, the Conservative Party conference police planning team will consist of three chief inspectors, five inspectors, eight sergeants, four PCs and four police staff, Mr Jamieson said.
There will be 24 police employees working in the planning team in total - 12 full time and 12 part time, he added.
A police force is facing a £1.5m bill to plan safety operations for the next three Conservative Party conferences, its crime commissioner has said.