The scheduling and commitment of power generating units vary in each country or grid-connected balancing area dependent on the generation portfolio, availability of plants, market incentives and many other factors. Having more standby reserve adds to the operational costs for utilities. ( In the case of China, these costs are not compensated through any market-based or price-incentivised mechanism.) Coal-fired power plants (large or small-scale), natural gas plants and hydro power plants (conventional and pumped hydro) together generated close to 97% of China's total electricity in 2009.