I have an idea I wish to run by the group. I am on the Agile Octopus with SolarPV but have no immersion hot water diverter. I was thinking about purchasing a diverter, but then had another thought. What about using Agile to achieve the same net goal?
At the end of each day I know how many kWh I have sent to the grid and been paid 5.5p per kWh. During the night time at about 3am, the octopus agile import tariff will be at it’s cheapest on average, for sake of example the cost is 5.5p.
If I exported all my surplus solar during the day time, and then purchased the (approx) equivalent back again during the night time to heat my hot water, surely from a pure financial point of view it has achieved more-or-less the same thing as a physical diverter? net-zero import/export of solar.
Of course there is variability in the Agile pricing. However per this website Octopus Agile London - Energy Stats UK the average night time price at 3.30am for London has been 4.44p! Cheaper still!
Is there a flaw in my logic?
This predicates being able to turn on & off the immersion heater with a crude timer or more surgically with a computer.
Alternatively, Energenie MiHome make a 3kW smart relay that can be controlled with IFTTT - and Octopus Agile have IFTTT applets that can switch the relay when your entered price thresholds are crossed.
I have seen increasing complaints on the Agile forum that IFTTT Agile applets fail to run at the correct time. Many users are seeking alternate control strategies not involving IFTTT.
I have been using Price threshold applets to charge Outlander using EVSE.
What I would like is an applet that would trigger multiple times (configurable) at the lowest price points.
If I say 7 units, it schedules the lowest 7 in the duration.
I had a chat with Phil and explained by reasoning. He has added it to backlog on Friday so I will give him a few days before I hassle him.
I configured it to use IFTTT when there is price plunge (manual intervention when electricity is cheaper than gas tracker price). eWeLink now need Pro account (10GBP) a year account for IFTTT integration. Might pay up one day.
Big question: how does VAT affect the price point ? Do you get paid 5.5p / kWh + VAT ? Agile display rates do not include VAT just so you know.
Thanks for all the replies folks. I’ve come to the conclusion that this idea is less economic than merely burning gas to heat the water on a typical day. Since octopus gas is about 2.7p per kW, it means the elec agile rate would need to be < 3p per kW to beat it (assuming a 10% efficiency loss on the gas boiler).
Having said that, I have analyzed the historical Agile rates and in the past 12 months the price dropped below 3p for 450 hours. So the cost of running a 3kW immersion heater would have been £12. Not bad!