Calculating error from accuracy score in Sklearn
From sklearn's documentation for the score function

Returns the coefficient of determination R^2 of the prediction.


R^2 is a measure of how well the variability of the data is explained by the model. So, at 0.97, the model is able to explain that really well. And yes, it is a measure of accuracy for regression models. However, you cannot construct confidence intervals with that estimate. 

accuracy_score is a measure of accuracy for classification models. Again, you cannot construct confidence intervals from the accuracy metric.