Dissassembly of some "newera credanet" night storage heaters.
For those who aren't familiar with storage heating, these are electrical resistive heaters which are operated during off-peak hours (overnight - a tariff known as economy 7 as it provided 7 hours of cheap power), and heat large thermal inertia bricks which are stored within an insulated cavity. The heat is then released gradually during the day.
These were introduced in the UK in the 1970s due to the proliferation of nuclear power and the excess production of electricity overnight. These were offered in place of coal or oil heating, where the use of cheap-priced off-peak electricity made them relatively economic.
However, they remain more expensive than modern natural gas heating. They are also inconvenient, as they leak heat when charged which can lead to overheating during the day (especially the morning), and must be charged overnight - this requires a degree of planning, as the charge for the next day must be programmed the night before.
The credanet system was an attempt at electronic control of storage heating. A computer would guesstimate a charge level based on the previous days usage, and top-up as required during the day using a fan-heat operating on full-price electricity. Now defunct, this system failed due to a ludicrously bad user interface coupled with the poor controllability of storage heating.