Is it possible to 'increase' your solar generation without increasing the size of solar array or at any cost to you?
It sounds perfect doesn't it? Whilst its obviously not possible to increase your solar generation without any actual physical change to the size of your solar array it is possible to change the way you use the generated solar power with different import and export tariffs to use.
In 2024 our 3.69kWp solar array generated 3779kWh.
SOLAR GENERATION IN 2024
We could have self consumed all of the 3779kWh solar generation through direct self use (ie consume straight away in the home, store in home battery for use later in the day and use any remaining excess solar by charging the EV). When we first had solar installed this is what we did because self consumption is what solar panels are for surely. But is it now the best way for us?
Making Import and Export tariffs work for you
In October 2023 we changed from Octopus Flux to the Intelligent Octopus Go import tariff and Octopus outgoing export tariff because our EV charging was increasing the cost of import considerably. The 3 hours lower cost period was too short for our EV charging.
The difference between the import and export tariffs changed considerably. We could now import at 7p/kWh overnight to charge the EV and home battery. We could then export at 15p/kWh during the day. This change in import costing less than export meant it made less sense to self consume our solar generation as we consume 2kWh's imported at night for 1 kWh exported during the day.
OCTOPUS FLUX IMPORT & EXPORT RATES
INTELLIGENT OCTOPUS GO IMPORT RATES
OUTGOING OCTOPUS EXPORT RATES
Our plan was to minimise the amount of solar self use so that we increased our export. To achieved this by:
* Not charging the EV off excess solar generation during the day.
* Recharging the home battery every night during the low cost period all year round (including the summer months)
By doing this we minimised solar self use to only the house consumption during the day. We could have reduced it further by running the dishwasher or washing machine at night but i'm not sure my wife would have liked that idea as much!
Of the 3779kWh generation we exported 3049kWh or 80.7% which is pretty good considering in 2023 we only exported around 60% of our solar generation when we also charged the EV in the summer directly from the excess solar.
EXPORT IN 2024
Did it make any difference?
Solar generation from our 3.69kWp solar system compared to per kWh of solar panels installed over 2024 was:
3779kWh / 3.69kWp = 1024kWh per kWp
From this we exported:
3049kWh @ 15p/kWh = £457
This is equivalent to an Import @7p/kWh of:
£457/ 7p = 6528kWh
Compared to self consuming the 3049kWh we exported its equivalent of an extra:
6528-3779 = 2,749kWh
In 2024 if we were to self consume all of our solar generation it would have been the equivalent to an extra:
2749kWh /1024kWh per kWp = 2.68kWp
That’s as if we had an extra 6.5 off 410W solar panels, or the equivalent to a:
3.69kWh +2.76kWh = 6.45kWp system
The Benefits
Rather than self use 3049kWh we've been able to increase use that to 6528kWh for no extra cost to us. We’re effectively using the grid as a storage battery by exporting our solar generation to it. But it’s a ‘storage battery’ that allows us to effectively take back more than we put in. This is because of Time of Use tariffs on Intelligent Octopus Go work in our favour and multiply our day time export by reimporting it back during low demand periods overnight.
For this to work well for you, you have to be able to reimport more than you could have self consumed. In 2024 we imported 7334kWh so it was above the 6528kWh we could get back for no extra cost from exporting 3049kWh at 15p/kWh.
Overall we averaged 98% low rate use because of our EV smart charging and home battery charging during the low rate period. Intelligent Octopus Go allows charging at 7p/kWh and our home battery has sufficient capacity to get us through the day without needing to import day time rate electricity.
GRIUD IMPORT CONSUMPTION IN 2024
Whilst our initial idea of solar was to be more self sufficient with our own solar generation, it feels like we are going against that idea by doing this. We may not use the solar power we generated but our neighbours would use it instead so it still helps the grid use less fossil fuels during the day. By import back at night during low demand periods its likely the import electricity is coming from renewable sources like wind at night because demand is lower therefore less fossil fuels are used to meet demand.
Will it be like this forever?
It’s doubtful that the export tariff thats compatiable with Intelligent Octopus Go will be higher than the import rate forever. Personally I’d say the future of solar will move towards more self consumption and storage of solar generated during the day to self use later (charge EV, evening home consumption). If I was a betting man I reckon export will move to very low in the day time with a higher rate at peak times to promote storage of solar to export later during peak demand periods.
It’s definitely a make hay whilst the sun shines situation. And the best part is that it currently costs you nothing extra to do if you already have an EV and compatible Intelligent Octopus Go EV or charger.