Unless your credit is being limited because you only have $50 of tax to offset, you should be eligible for the $300 credit that you refer to.
It's possible that you entered the $300 in the wrong place in the home energy credit portion of the program -- there are a lot of options there. Go back and check your entries.
With TurboTax Online open,
- Click the Pick up where you left off button, if it’s present
- Let the whole page load
- Click the Federal tab in the left pane
- Click the Deductions & Credits link near the top
- Scroll down to Home Energy Credits and click the Edit box to the right
- Answer Yes on the Energy-Saving Home Improvements page
- Continue through the interview until the Tell Us How Much You Paid for Energy-Saving Improvements page
- Make sure your $300 amount was entered in Energy-Efficient Building Property
A stove using the burning of biomass fuel to heat your home, or heat water for your home, with a thermal efficiency rating of at least 75% is eligible for the $300 credit when claimed on line 22a of Form 5695.
