Does a boiler scrappage scheme make sense?

I saw this in the Guardian yesterday - leading UK environmentalist Tony Juniper encouraging the British government to introduce a boiler scrappage scheme. Such a scheme would offer householders grants to replace their old boilers with new, high efficiency ones. It would work similarly to the UK car scrappage that offers money to those trading old cars for new ones.

Juniper writes:

The simple idea is that by replacing the country's old, inefficient gas boilers it would be possible to achieve a major environmental benefit and conserve a valuable resource while at the same time creating employment and economic activity...
 
...Reheat Britain suggests that a limited and temporary fund is created, mostly from public sources but perhaps also including contributions from boiler manufacturers. It would work along similar lines to the car scrappage scheme, and it is estimated that an incentive of about £200 per boiler would be needed.

  Juniper says that replacing a G-rated boiler with an A-rated condensing boiler with better controls could cut household energy bills by a quarter. He says that the carbon cost of making and fitting new boilers would be quickly compensated for by the high efficiency of new, A-rated units.

He also speculates that the idea could be slow getting approval in political circles because of the absence of lobbying power in the heating sector compared to the motor industry.

A boiler scrappage scheme is a sensible idea, but might not be necessary if governments adopted a pay-as-you-save scheme that would enable householders to energy upgrade their homes (with measures including new boilers) at no up front cost, and repay the work over time on their utility bills.