How to utilize user survey answers and the actual usage in forecasting power usage using LSTM?
Check out the example "Multi-input and multi-output models" here in the documentation. It gives an example how to combine an LSTM time series model with additional input. You would use separate input layers for the power usage and for the survey data. After running the power usage data through the LSTM you combine the results using "concatenate". 

(You can ignore the Embedding layer in the example since your power usage data isn't text data.)