The union claims it will lead to the closure of power plants as Eskom would require less coal to produce electricity, ultimately resulting in job losses.
He said that coal is a dying industry that is constantly facing challenges and bleeding jobs. There was also misunderstanding about the process of Monday's court application.
The union alleges that jobs will be lost and that consumers will have to pay more for electricity if the contracts are signed and renewable energy becomes part of the country's power grid.
In the absence of an interdict‚ and with the court having expressly informed the parties at court that it would not grant such an order‚ nothing prevented Eskom and IPPs from signing the agreements as scheduled by me for Tuesday‚ 13 March 2018.
This after Numsa and Transform RSA obtained an urgent interdict in the High Court in Pretoria to prevent Eskom from signing IPP contracts.
"The IPP roll-out will raise the cost of electricity dramatically, because IPP's cost much more than coal-fired electricity", Numsa said.
In a study about the cost of new power generators in SA, the CSIR argues renewables such as solar PV and wind are a "mass manufacturing play".
The order is another setback for energy developers including Denham Capital-backed BioTherm Energy and ACWA Power International that have been waiting for deals to be signed since 2016. The oldest coal-fired power plants are fifty years old and have already exceeded their expected operational time.
At a media briefing announcing the signing ceremony last week, Radebe said South Africa had reached a milestone following a protracted period of uncertainty.
She points out that as has been demonstrated through three competitive bidding rounds, the renewable energy industry is in a strong position to contribute to the South African economy through job creation, advancing the transformation agenda, improving rural livelihoods and attracting foreign direct investment.
Yelland, the investigative editor of EE Publishers, on Tuesday described the court bid as a "delay tactic", saying the move towards renewable energy is a global trend which would not leave South Africa behind.
"The usage of different types of energy supply‚ which includes renewable forms of power generation‚ is in line with the energy policy".