Another free way of doing this is to use the power meter outside your home.

• turn everything using power off
• verify by ensuring the power meter is no longer moving; no electricity consumed
• record current reading
• turn on tv for some period of time
• record new reading

Calculate usage as difference of the readings divided by how long you ran the tv for.

Some places make you use their app. I’m thinking the Kodak printers at places like Walmart and Staples.