Perverse incentives

[undyingking]

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.

Comments

[hatmandu.livejournal.com]

My understanding was that the vast majority of combi boilers can't be used with solar thermal - IIRC something to do with modulating temperatures – but there are a couple of manufacturers who do make solar-friendly combis. (We're not on gas but I looked into it all before our renovation last summer; we ended up with a wood pellet stove with thermal store, and hope to plug solar thermal in when our finances recover.)

[undyingking.livejournal.com]

Hmm, I was told that any combi could, with a suitable adapter (essentially, an interposing pumped and switching cylinder). Well, I'll look into it more deeply if we ever get round to it…