NEW YORK ( TheStreet) -- Call it the Barclays Flare Up. Three solar firms that received a ratings upgrade to outperform on Monday from Barclays Capital watched their shares soar towards the sun in the week's first session. Some more skeptical solar industry experts have been left scratching their heads by the recent fervor. They wonder, with a major dent to the solar industry possibly coming soon in the form of changes to the German feed-in tariff system, are solar investors getting out ahead of reality? Heavy trading and huge one-day price gains were the norm for JA Solar ( JASO), SunPower ( SPWRA) and Suntech Power Holdings ( STP). JA Solar was up 12.50% on Monday, or a gain of 55 cents to $4.95, with a whopping 16 million-plus shares traded, versus an average volume of 5.6 million. SunPower, still to reveal the extent of its ongoing accounting issues on Dec. 16, was up 9.6%, or a little over $2 to a closing price of $24.45. Suntech Power was up 10.8%, or $1.66, to a close of $17.05. While the Barclays upgrade benefited these three firms directly, ReneSolar ( SOL) actually had the second-highest gain on the day, climbing to its highest price in over a month on Monday. ReneSola was up 12.2% on Monday, or 50 cents, to $4.60. In late October, ReneSola had hit a three-month low of $3.57.