We have 10 off 550W solar panels installed in our garden with an 8.2kWh battery and inverter in our garage. We are with Octopus as our energy supplier on the Flux tariff for electricity and the fixed tariff for gas.

I have thought about how to use technology to further reduce our use of energy. To start with, I used the Flux tariff to write software using Python that enabled the battery to be charged in the early morning when the price was low and discharge in the evening peek period when the price is high. This has the main benefit of helping to stabilise the grid network. It also helps save energy during the winter period by ensuring the battery is charged up to service the home particularly when there is little sun; this also reduces the cost a bit. I use a Raspberry Pi to run the software. I limit the discharge to ensure that there is sufficient energy to supply the home during the night, this is about 30%.

Then I decided to use the MyEnergi eddi device to control the hot water tank. This boosts the temperature in the tank soon after the battery charge has finished in the morning and maintains the temperature when the solar panels have recharged the battery. This ensures that hot water is available for use during the day. When we started this we found that we had to replace the original 70 year old hot water tank because the immersion heater had broken and replacing that would break the old tank. This helps save energy during the warmer spring, summer and autumn periods by enabling us to turn off the gas boiler, including the pilot light, and only use the gas for some cooking purposes. Gas usage is down to about 50kWh per month (10% of normal) and the overall cost tends to be in credit or close to 0.

Any energy usage from the grid is offset by the export of excess energy from the solar panels. Ensuring the battery is charged up at the beginning of the day maximises the export of excess energy. This is offset a bit by the use of the MyEnergi eddi, which uses about 30% of the battery energy on average. Still this avoids the use of gas to maintain the temperature and is more effective. We don't yet know how well the eddi device will work in winter, maybe we will have to boost the temperature with gas in the afternoon if there is no sun.

Our energy bill for April was £69, May £6 and June £29 in credit - so it appears to be working.