A matter of scale, distance & speed. (assuming we are talking about electrically driven engines like ion drives or the proposed EM engine.)

If nothing else, the sun gets weaker the further away you get. Out at the edges of the solar system it's almost negligible.

Given that mass directly effects net thrust & fuel range, smaller craft working in the inner solar system may well be better off sticking with solar over a bulky reactor.

Larger and or longer ranged ships should start to favour fusion reactors and such.

Unless of course they manage to miniaturise the fusion apparatus, or perhaps harness quantum effects like matter/anti-matter. etc. etc.

Surface area to volume ratio also starts to shaft solar power the bigger the ship gets too. The panels would have to get exponentially bigger along with the ship/engines.

I couldn't tell you exactly where, but there will be natural tipping points between the practicality of one over the other.

Edit: The calculation would mostly be the ratio of energy produced to mass of the generating apparatus. The point where a fusion reactor (inc it's fuel) can produce more required power per unit of mass than solar cells (and associated gubbins), is the point where it becomes more efficient for most spacecraft.

Though solar still has a clear advantage where indefinite operational duration is a factor. (fusion requires fuel, albeit in small quantities)

That is absolutely not true....all of it.
First, it's only close to true if you only count the direct costs of production, and ignore all the cost to mitigate the damages energy production causes.
Second, even then it's not true. I put in a solar system on my house around 10 years ago. It paid for itself in savings in under 8 years, and has a lifespan of over 20 years. That means, compared to coal, coal, and coal, it's incredibly more efficient and cheaper.

Geothermal is the MOST efficient and 'clean' form of energy out there. Where did you get your information, a BP flier?

So, if you should swap energy sources when they make (economic) sense, that would have been >10 years ago. If you count all the costs involved with other energy sources, not just basic energy production costs, it would have made sense to switch around 40+ years ago.

*promote exploring the solar system....but does this mean they scrapped the mission to retrieve Discover One?
It will certainly be interesting to find out if the red cracks are red from bacteria or something else.

I'm sure i've been hearing for years that it was likely there was a large planet far out in the solar system. Maybe i'm getting mixed up between guesswork and/or findings that were later disproved, but the media seem to find this a lot more of a revelation than the astronomers i know.

Well... I think that pretty much settles it then, doesn't it?

I propose that, henceforth, we refer to the newest member of our solar system as "Dorris"at every available opportunity, and let the viral nature of the internet do the rest.

NAOS

Sadly I'm right there with you.
When the international climate agreement was made public recently and I saw that what they were pleased and proud of was an agreement to somehow (they didn't say how) stop the rise in CO2 at almost exactly the level that's agreed on is the point of no return/the level that they think will start all the feedback loops making mitigation or survival impossible, which somehow no one seems to understand means they agreed to do NOTHING besides drive us directly over the cliff. If that's the best we can hope for, a non binding agreement to wait until it's too late to do anything that might save the species/planet, we might as well just say screw it and enjoy the little time we have left. How much comfort will driving a Prius give you when the clouds of Hydrogen Sulfide rise from the ocean?
This is from a guy with an expensive solar system who grows most of my own food.

'Too early to start drinking?' Never! I understand all those words, but not when you string them together like that....and I don't drink.

thanks man.
that rabbit hole goes much further.with the mention of dee and kelly who are responsible for the enochian (or angelic) alphabet,and also enochian magicks.which leads to crowley and the thoth tarot deck.

there can be some correlation between lovecrafts "old ones" and angels.we are not talking the cherub,fairy godmother type angels of childrens stories,but angels who are messengers of god,where gabriel is mentioned as being the size of a solar system an to gaze upon his actual countenance would render the observer mad.

none of that warm and fuzzy from fairy tales but horrors.

i loved studying those esoteric books but they always creeped me out,probably why i love lovecraft.

Most of us have came to this conclusion when we realized I couldn't spot the other planets when we looked up in the sky at night. Only a troglodyte would assume that the popular solar system depictions are up to scale. The one thing that stuck with me as a child is when I was told that there are billions of suns in our sky. We just call them stars. That blew my mind.

Cool video nonetheless.

Congratulations! Your video, To Scale: The Solar System, has reached the #1 spot in the current Top 15 New Videos listing. This is a very difficult thing to accomplish but you managed to pull it off. For your contribution you have been awarded 2 Power Points.

This achievement has earned you your "Golden One" Level 26 Badge!

To Scale: The Solar System has been added as a related post - related requested by jimnms on that post.

Riding Light: A journey of a photon through our solar system has been added as a related post - related requested by jimnms.

*related=http://videosift.com/video/Riding-Light-A-journey-of-a-photon-through-our-solar-system

Your video, To Scale: The Solar System, has made it into the Top 15 New Videos listing. Congratulations on your achievement. For your contribution you have been awarded 1 Power Point.

This achievement has earned you your "Pop Star" Level 32 Badge!

As a side note, I noted in the comments:
Heck people don't get the scale between the Earth and the Moon. The distance is so great that all the other planets of our solar system could fit in between the Earth and the Moon, while at aphelion anyhow, and have a bit of room to spare. If you arrange the planets pole to pole, then you can do it during the average distance of the moon's orbit. You can't pull the trick off while in perigee though as it gets about 27 kilometers too close, though this sort of shows the scale of the orbital eccentricity.

Well, allow me to respectfully say that you (and he) are wrong.
Absolutely I would still save money without the grid. I already have paid to have a small battery bank in my system (>1KWH), so it wouldn't cost me much more to be completely grid free. As it is I barely send power to the grid, as I use most of my electricity as I produce it by doing housework during the daytime. (EDIT: If @Asmo did that, maybe just by using timers on large appliances to run them during the daytime, he would save a lot more, like up to 4.5 times as much as he saves today.) In the short run I would not save as much as I do currently, because I would need to buy more panels and a larger battery bank, and the batteries would need replacing sooner, but it would still be a huge savings in the end over buying grid power. The suggestion that it's not economically viable without the grid is simply wrong.
Once flywheels become popular, it will be far cheaper than it is today to store your own electricity, I'll probably get one to replace my batteries when they eventually die.
EDIT: A micro-hydro system could also store the power cleanly, but requires 2 large storage tanks, one raised as far as possible above the other, and a pump/turbine to move the water. For those with the space, that seems a good solution for power storage, and it's how some electric companies do it on a large scale already.

EDIT: I did the math, and to be completely grid free would cost me about $3000 more, and the upgrade would pay for itself in 2-3 years. Hmmm, now you've got me thinking.....Oh yeah, I forgot, my system can't run my large welder, the electric oven and stove together, or the hot tub directly, that's why I stuck with a grid tied system in the first place, I use too much electricity at once sometimes. Solar systems DO have some limitations, mine can only put out 6500 watts at once, max.