Vanderbilt and the Yeggman. Vipers. Vigor, the Hammersmith wonder.

Heard recently that the govt is going ahead with bringing in a subsidy for domestic solar hot water systems, whereby you get paid 18p or so per kWh of heat that you generate (as well as saving off your gas bill, of course).

It's estimated that a typical 20-tube installation on a south-facing roof will pull down somewhere around £400-500 for you per year through this subsidy: not bad.

There is a snag, though, which is that the subsidy isn't payable for installations on houses with combi boilers: only for those with the more traditional cylinder-plus-boiler setup. Not because there is any technical drawback to using solar-heated feed to a combi, or efficiency penalty, or anything like that: that's not an issue. It's simply a policy decision.

This is probably a bit galling for anyone who thought they were being nice and eco-friendly by installing a combi boiler, as previous govts persistently urged us all to do. But fair enough, maybe they are thinking that encouraging solar adaptation of older boiler systems is going to clean up more of the low-hanging carbon-emission fruit.

But this is where the title of this post comes in. It'll cost you about £3000 (say) to rip out your lovely efficient new combi boiler and replace it with a cylinder-plus-boiler system. With the subsidy guaranteed to rise with inflation for 20 years, you'd repay that and be quids in before too long.

Hmm.

As the Mobiot piece about feed-in tariffs was the most popular of my miscellanea of the other day, I thought you might be interested to read this riposte to it by Jeremy Leggett of SolarCentury. He has of course a powerful vested interest in the uptake of solar electricity generation, but even so I found some of his arguments useful.

I find it very hard to evaluate a situation like this where debate proceeds largely by contradictory counter-assertion.

Clearly, either the amount of electricity that can be produced is either risible, or it's significant: it can't just be a matter of opinion. So who is correct here?

On the other hand, their rival interpretations of the German situation are open to speculation -- has Germany reduced its tariff because it's been unsuccessful, or because it's been successful? In the absence of German testimony, I could find either explanation plausible.

As before, analysis from people who know more about all this than me is very welcome!

Just a few things that have caught my eye lately.

• You may think you did well to write a book in a month last November. But this guy writes upwards of 3000 books a month. "He says it takes about 20 minutes to write one." And they sound like gripping reads, too. Let me know if any of you own a copy.
• Online dating with algorithmic matching is increasingly popular. But the science involved may be questionable. Particuarly when unsemly rows break out between the rival companies. Here's a neat summary -- "eHarmony asked the Better Business Bureau to stop Chemistry.com from claiming its algorithm had been scientifically validated". You'll need to log in to see this one, I think.
• Google run an internal prediction market, whereby staff make predictiosn about how various business indicators are going to move. Well, they would, wouldn't they: but here's an brief analysis of some of the interesting weaknesses they've found in their market -- "this research changed my mind about the importance of open-plan seating".

I wa laid up all weekend with a stinking cold, meaning that I missed a friend's 40th do on Saturday. As if that wasn't bad enough I've got to go to the dentist this afternoon. I bit down too hard on something a while back (curse you home-made bread!), and managed to crack one of my molars, and now they're going to drill out that whole cusp to prevent the crack spreading further.

Last time I had something done on my teeth was wisdom removal around ten years ago, so I guess it's about time maybe, but it's still kind of galling and I'm really not looking forward to it. Hopefully sweet anaesthetic will ease the pain...

This got me thinking about dental insurance. In general I'm not a great believer in specialized insurance like this. I figure that they wouldn't be running it if they didn't expect to make a profit, so unless you're particularly risk-averse (eg. you don't have any way of covering a possible layout) you're better off just saving the money.

However it struck me that dental insurance is a bit different, because with a dentist it's effectively up to them what treatment you have. If you don't have insurance but just pay on a job basis, it's in the dentist's interest to recommend excessive or unnecessary treatment, because that's how they make their profit. (I'm sure most of them wouldn't do so, but that's always going to be at the back of your mind, isn't it?) Whereas if they're also providing your dental insurance, it's actually not in their interest to recommend treatment unless it would prevent more expensive and unavoidable treatment later. Of course if you take this too far they would never give you any treatment at all, just keep raking in the premiums, but in practice under our particular plan we do have to pay some money towards the fillings etc, so presumably that covers their costs at least. (Please tell me that adamsmithjr's already done an Under the Covers Economist on this...)

This does make me think though that dentistry is a dream business provided you don't mind having to bend over people's fetid breath all day long. But that's quite a big proviso, isn't it?

Edit: Had the filling done now, and it wasn't too bad -- seems to have come on quite a way since the last one I had, which must have been upwards of 20 years ago now.