Sorry, I didnt explain myself cleary, a contactor is a way of getting a small switch (your heating controller) to switch a bigger load, like the electric heating or the immersion heater, its like a relay if that helps? Basically its got a switch in there, and an electromagnet, when you power up the electromagnet (with a small current), it pulls the switch in and turns on the load (which is a big current), you have two off the in the bottom left of the fuseboard, one with a red band at the top (Made by ABB), and one with a blue band (Made by Hagar)
If you have standard panel heaters, and you are not making use of the cheaper night rate to heat your water, then having the E7 tarriff is probably costing you money because you pay more on the day rate to have that. It varies, but the break even point tends to be a quarter of your units on the night rate, any less and it costs you more, and I think it may have even got worse than that since. Its designed for people who have storage heaters which charge up with heat overnight, mainly, although these days, you might find a benifiet if you charged an electric car overnight
If you have standard panel heaters, and you are not making use of the cheaper night rate to heat your water, then having the E7 tarriff is probably costing you money because you pay more on the day rate to have that. It varies, but the break even point tends to be a quarter of your units on the night rate, any less and it costs you more, and I think it may have even got worse than that since. Its designed for people who have storage heaters which charge up with heat overnight, mainly, although these days, you might find a benifiet if you charged an electric car overnight