Automating Mk2 Router with light sensor

I live in Spain and any excess electric that I produce and gets put back into the grid, I get charged for at the going rate. To alleviate this problem I am going to install Robin's Mk2_PV_Router_mini3 to soak up my excess power. I would like to take this a stage further and wondered if it would it be possible to include a light sensor into the arduino uno and a time clock. I have my pool pump, storage heaters and water heater all on timers to ensure that they are never on at the same time. My panels produce about 1.6 - 1.7 kW  on a sunny day which is enough for all my appliances when run one at a time. The water heater can take up to 2 hours, pump 4 hours and the storage heater 10 hours. I am thinking that only if it is sunny, the heater and the pump come on when it is sunny enough, controlled by the light sensor. If it is not sunny, then everything is delayed until it does become sunny. There has to be some logic involved that eventual turns the heater and pump on by a set time, even if there has been no sun at all. In the winter, my storage heater will be my dump and in the summer my storage dump will be a bank of 200 watt light bulbs until I figure what to use the excess dump for (heating my swimming pool). Outside of these times, the dishwasher, washing machine, ironing etc can be done as and when there is sun. Has anyone else considered this and maybe have a working solution.?