New analysis of the proposed goal reveals that wind farms already under construction and projected rates of rooftop solar installations will alone lift renewable energy's share in the Victorian electricity mix to 18 per cent by 2020.

Last month the Andrews government said it would pursue at least 20 per cent of the state's electricity generation coming from renewable energy, such as wind and solar power, by decade's end. Premier Daniel Andrews said at the time that if the state could do better, it would.

The government is seeking feedback on the 2020 goal, and also one for 2025, as part of a plan to encourage more renewable energy it has promised for later this year.

About 12 per cent of Victorian power currently comes from renewables, with brown coal generating 85 per cent.

An analysis by consultants Green Energy Markets found that an 18 per cent renewable energy share was essentially already locked-in for Victoria, based on what was already in the pipeline.

The author, the firm's director Ric Brazzale, said as a result a 20 per cent goal would be met "really easily".

Mr Brazzale added that basing the target on how much renewable energy is generated rendered it ineffective because Victoria could just import coal power from other states via the national grid.

Instead, he said the target should be based on the amount of power consumed in Victoria.

The firm's analysis also found that if one of the big ageing brown coal power plants in the Latrobe Valley was to close before 2020, renewables would hit a 22 per cent market share by 2020.

The findings were broadly consistent with work by Environment Victoria, which in its submission said a 20 per cent target would be little more than business as usual and "would not require any significant effort by the Victorian government and therefore cannot be regarded as ambitious".

Environment Victoria recommended the state instead adopt targets of 30 per cent target for 2020 and 50 per cent for 2025.

The group found those targets would be met with the additional rooftop solar installations, construction of all wind projects with Victorian planning approvals and the retirement of one coal power plant by 2020 and another by 2025.

But elsewhere several industry groups in submissions questioned the rationale for setting a state target and what overlap it would have with the national scheme, which is geared to see 23 per cent of Australia's power come from renewables by 2020.

The Electricity Supply Association of Australia said without bipartisan support the state target would do little to encourage investors. And depending on how it was implemented could lead to higher consumer bills and potentially divert investment from the national scheme, causing it to fail.

The Victorian division of the Minerals Council of Australia said renewable energy should win its share in the electricity market "on its own merits" and not by mandatory targets and feed-in tariffs.

A spokeswoman for Energy Minister Lily D'Ambrosio​ said the 20 per cent goal was a minimum target and the government looked forward to reviewing submissions on what the 2020 target should be.