Hacker News Reader

Comment by Retric | Hacker News Reader

That is the exact use case where solar roofs on EV’s become very useful. However you can “jump” EV’s, supply power to their 12v system and then charge off of another cars 120v plug, or a portable generator etc.

View on HN

Similarly, I've always thought it's a no brainer for any ICE car to have a solar roof. At a minimum it can keep a 12v battery from dying over long parking durations or high parasitic drain, and at best it could like, keep a container refrigerated or something.

I’d rather pay $2,000 less for my Honda HR-V than get a solar roof. But I agree it seems like a very nice option for those willing to pay more for their vehicles.

2k is IMO a poor price point as it’s too much for the minimal utility but not enough for meaningful power. IMO solar roofs are useful at the low end for ~400$ ICE cars could top off their battery and run a solar fan to keep the temperature down when parked in the sun. Not a huge deal, but still a nice luxury feature.

Or a significantly more expensive solar roof could add meaningful highway mileage per year. You both largely offset its cost via less charging and have the option for a low speed crawl to a charging station.

It's worth noting simple solar 'trickle chargers' can be had for less than 100 bucks, today. They are awesome for such things like additional confidence while overlanding in a remote location, or for a trailer with a winch, or an electric boat lift on a dock without shore power.

I'd be surprised if solar panels in the roof were less than $2,000. An android-auto enabled head unit is like $500. Heated seats are often $1000 and that's "just" resistive wire. A cover for your truck bed is like $700. Premium carpet mats are $250. Unlocking your tailgate using a remote beeper instead of a physical key costs $300.

> IMO solar roofs are useful at the low end for ~400$

So I agree with this, but I don't believe that would be an option, at least without some DIY aspect.

Car options are priced independently from what they actually cost to manufacture. A cheap luxury car will often include a host of features that cost quite a bit when you added as features to a lower end car. And sometimes it’s the reverse where missing features in luxury cars ends up being almost as expensive as the cheap cars they come standard in.

It’s a combination of price discrimination and the overhead of having multiple different specs being manufactured independently of whatever the actual differences are.

> at least without some DIY aspect.

Solar car battery chargers already exist for less than 30$. I’m assuming the overhead of including it into the cars design and modifying body panels etc significantly increases costs. But it’s the kind of thing Subaru could add to every car for diversification without significantly impacting final price.

Yep. So I’m expecting it to cost me $2,000 as the consumer, and I wouldn’t want to spend that. If costs some trivial amount, I’d love to have a battery that basically never dies.

Continental America averages on the order of 4.5kWh/m^2/day total solar irradiance.

A clean, car roof sized solar panel in direct sunlight all day would be good enough to offset parasitic drain with maybe enough left over to charge a phone or two but not much else. Not worth the cost (or the variance given you’re not always going to park in direct sunlight for 8+ hours).

I would expect people in sunny areas would be more interested in a solar car.

The recent solar Prius has a small roof and gets a few miles of range per day. Things get more interesting on a van/full sized SUV with a far larger roof.

I once drove back to SF from Castle Lake with a dead alternator by hanging an 85W portable solar panel over the rear window of my mx-5, connected to the battery in the trunk.

It supplied enough juice to run the car with no accessories most of the way back, until a combination of overcast sky and uncooperative route direction started making the car hesitate at the slightest throttle input.

So it'd definitely give a little MPG boost by taking a load off the alternator, in addition to keeping the battery topped up like you said. I was tempted to epoxy a cheap flexible one permanently on the trunk-lid. With the trunk-mounted battery it'd be trivial.

That story brings me great joy, thank you for sharing.

or run a small ventilation fan in the summer.

Concrete numbers you could expect (30-40W): https://youtu.be/usqSJ7zbTLQ?t=513

Solar roofs provide very little power, generating less than 5 miles a day in charge.

That’s to do to the tiny amount of solar added to most cars “solar” roofs which then exclude the hood of the car etc.

It’s a lot more interesting on the ~8m2 roof of a van / full sized SUV than a ~1.5m2 center roof of a car.

Reply on news.ycombinator.com