Another thing to consider with battery storage (at least with ours) is that we benefit from economy 7. If the batteries are not fully charged during the lower light winter days, we can charge the batteries overnight using the lower rate economy 7 electricity and then use the battery and solar in the daytime. At present the economy 7 tariff is 11 pence cheaper for the night rate. We generally use around 13kwh in the daytime and if that’s all coming from the battery, that’s a £1.43 saving per day. In reality we are finding that we are saving ourselves the purchase of around 200 day units a month in winter months compared to pre solar and battery install. Our system was designed to export as little as possible to the grid since they’re only paying about 5p per unit generated and they’re selling it on for circa 30p a unit which in my opinion isn’t cost effective.