One of the first owners of a Tesla Solar Roof says he’s “amazed” by the product, revealing the surprising usage statistics behind the company’s blend-in tiles. Tri Huynh, a senior manager at Nvidia that made headlines in March when he first shared photos of his installation, gave a new interview on Saturday detailing his experiences.

Huynh priced out a traditional roof with solar, sans batteries, $70,000, with around $50,000 of the cost going to the roof. Solar roof was $100,000 with three batteries, where the roof itself cost about $85,000 for a 1,000 square-foot roof and the batteries cost $15,000. That means Huynh paid around $35,000 extra for a roof with solar capabilities. Huynh claims the roof has around 70 percent active tiles, with 30 percent non-solar tiles. Took about three months to get utilities company to connect, largely due to a company backlog. Once turned on, took a day to get started.

See also: Tesla Solar Roof: 8 Things You Don’t Realize Until You Own One

Huynh’s bill normally comes to $350 per month for a four-person house, with the biggest usage coming from running the air conditioner and charging his Chevrolet Bolt and Tesla Model 3. His first bill with the solar roof came to $90, which Huynh said is “a little high,” but this bill only partially covers his time with the roof. The power company gives a rebate of two cents off the gas bill, rather than buying it back outright, so Huynh and his wife “try to avoid” sending back excess energy at the end of a day. With the sun shining, the roof can produce up to 10 kilowatts of power, charging the three Powerwalls in several hours, dropping down to three kilowatts on a gloomy day and normally producing around seven kilowatts.

The roof has already led to the family changing its habits, leaving the electric car behind during the day so the car batteries charge alongside the Powerwall during the day. Huynh notes that the roof is so tough he hit it with a hammer to test its strength, noting that “I think there is a little premium to it, but I think it pays off really quick, and according to Tesla you have lifetime warranty on the roof.” If the roof drops below its expected performance, Tesla dispatches employees to clean and conduct any repairs.

Huynh recommended the roof to viewers, noting that “if you need a new roof, the solar roof makes absolute sense, especially if you’re replacing the roof and you want solar.”

It’s a sentiment echoed by other owners, like Amanda Tobler, whose house was featured in a Tesla shareholder meeting.