Chris Lau, Kapitall: Solar stocks rise and fall with the markets. But can investing in solar add a little shine to your portfolio? Given the massive ups and downs in solar energy stocks over the last few years, it is hard for investors to believe things may be different this time. The solar energy sector previously looked to be in an unsustainable bubble. [Read more from Kapitall about investing in solar: Should Value Investors Warm Up to These Solar Stocks?] But generous and abundant subsidies, high demand, and high margins invited firms to supply more. When prices dropped for solar panels, weak players filed for bankruptcy and the lower supply helped stabilize the industry. In the US, solar power generation is becoming a more significant source of energy. Coal and natural gas sources now need to compete with solar power, which may help explain why utility stocks are poor performers this year. Investing ideasSolarCity (SCTY) is on a tear. Shares rose 25% on the week, closing recently at $47.18 and not far from a high of $52.77 reached in May of this year. The company’s latest forecast is only slightly better than previous expectations, so should investors be considering SolarCity now or waiting for a pullback? Only Trina Solar (TSL) is outshining SolarCity in the short-term. In the one year period, Trina and SolarCity are up more than two-fold: Click on the interactive chart to see data over time. Trina may be up because the Chinese government is giving a 50% value-added tax rebate to solar manufacturers for the next two years. China is also imposing a tariff of just 6.5% for most of the polysilicon suppliers coming from the US. The lighter tariff suggests that trade between the US and China will not be hurt as badly as previously thought.