Home battery with IOG
We recently got an electric car and we've now switched over to the intelligent octopus go tariff, with cheap overnight rates for EV charging but it comes with its more expensive day rate.
I am wondering whether a house battery is worth investing in (on its own without solar for now) or even one of the newer plug&play type battery to minimise installation costs. Charge them overnight on the cheap rate and discharge it during the day. This should offset the unavoidable daytime power usage such as fridge, tv, oven, kettle, computers, lights etc to the overnight rate.
That's the idea anyway... some approximate numbers to follow:
Overnight rate at ~10p/kwh, daytime at ~30p/kwh, results in a difference of around ~20p/ kwh. I think we used around 150kwh during daytime hours in the last 30 days (though this may be skewed from daytime EV charging when we were on a ~20p/kwh fixed tariff before IOG). But ~20p saving on ~150kwh, works out to ~£30 per month or ~£360 per year savings?
A 5kwh (150kwh/30days) home battery installation cost would be around ~£4k? So payback time would be around ~11 years (not accounting for inflation). Which exceeds the life of the battery(~10 years?)... So not worth it?
Do my numbers seem right? Has anyone else done this calculation? Anyone with a battery and EV without solar have real numbers to share?
Hmm where to go next...
- feed in tariffs.. bigger battery, charge during cheap, feed in during peak calculation.
- adding in a solar installation and generation into the calculation.
What fun.