Under the NDRC's renewable energy plan set out in 2007, China would have 1,800 megawatts of installed solar capacity by 2020.
But Wang Zhongying, assistant director at the NDRC's Energy Research Institute and head of its Renewable Energy Development Center, said the country was likely to far exceed that.
"The goal that we made originally is probably too low," he said at a solar energy conference in Shanghai. "By 2020, we can reach 10,000 MW or more."
He cited an international aspiration for countries to get 1 percent of electricity from solar by 2020, which would mean a target of 40,000 MW for China, which he said was too high.
"China could reach 10,000 MW or higher, maybe 20,000 MW.
He stressed that the forecast was his own opinion and not an official target.
At the end of 2008, solar power capacity attached to the grid was less than 100 MW, or 0.01 percent of China's entire installed capacity.
China is massively dependent on coal, used to generate around 80 percent of its power, but hopes to lessen coal's dominance by using more hydro, wind, nuclear and biomass.
The government is expected to unveil an economic stimulus package for renewable energy within the next few months.
Shi Dinghuan, president of the Chinese Renewable Energy Society, said the 2020 goal for renewable energy would be revised under the new stimulus plan to more than double the 2007 plan.
Even with a tenfold increase in its 2020 target, solar would play a much smaller part in China's overall power mix than those other energy sources. Under the original plan, biomass and wind were set to reach 30,000 MW by 2020, with nuclear at 40,000 MW.
China has already more than tripled the 2020 target for wind to 100,000 MW and is expected to easily surpass its nuclear target.
The revised target for wind could be 100-150 GW, Xinhua news agency quoted sources close to the plan.
Firms with exposure to China's solar sector include Suntech Power, Trina Solar, ReneSola, China Sunergy, LDK Solar, Yingli Green Energy, and Solarfun.
China announced the plan to grant subsidy to pilot solar power projects attached to buildings in March. Industry officials applauded the effort, but also said the subsidy plan has its own problems.
"It's a great policy, a positive sign that the government wants to support the development of the solar industry. But it's difficult to implement the policy," said Wang from the NDRC's Energy Research Institute.
Beijing said it would provide 20 yuan per Watt-peak (Wp) of subsidy for solar power projects attached to buildings that, in addition to other requirements, have capacity of more than 50 kiloWatt-peak (KWp).
Wang said the central government was studying detailed guidance on the policy, which potentially could push for a big stride in the solar industry's development.
Industry officials said many companies have already shown enormous interest in the subsidy, including solar companies and real estate developers.