Solar PV has never been as attractive as it is now. Prices are at an all time low, the feed-in tariff is making the payback excellent and the cost of mains electricity is still going up. Whilst solar generation technology has improved, the storage methods for the power you generate has lagged far behind.
An average home might use around 10kW/day, whilst a typical 3.5kW panel system would produce something like 10kW on a summers day and only 2.5kW on a winter day. So on the face of it, the panels would produce the majority of your energy needs, but there is a snag – for the majority of us domestic electricity consumers, we use much more electricity in the evening than during the day, and there tends to be less sun, or indeed no sun, at these all important hours.
You can imagine a scenario for example, where only 5kW out of 10kW generated is used during daylight hours, but then 5kW is used after dark, powering the oven and the TV and the washing machine. You have two choices – to displace the generated energy to later in the day (i.e. alter the supply), or to move the demand forward to when the energy is generated (i.e. managing the demand).
This is one way to use your generated electricity when it gets dark. There are various types of battery storage system on the market, but they all come up against several major hurdles. Firstly, any battery system would have to charge and discharge thousands of times in its life. This is beyond the capability of many batteries, and this means regular replacement. Cost of the battery is also prohibitive for many, with the cost per unit of storing the energy, all said and done, being more than the cost of just using grid electricity.
Working with the grid
Instead of storing the energy you create, you can look to export it to the grid. Now for most people, who don’t have an export meter, it is assumed that you export 50% of your generated energy back to the grid anyway, but for those who actually use even less than this, it might be worth installing an export meter and getting more from the exported electricity. If you tend to be away from home a lot in the summer for example, this could be worth considering. Unfortunately the export tariff is rather low, so you aren’t likely to see big returns via this route. If you can, you should try to utilise the energy rather than exporting it, as the cost per unit is around three times the export tariff.
What is becoming much more popular now is what is called ‘soft storage’. This means that instead of storing the excess energy you generate in the form of electricity, you can store it in other mediums.
Using a diverter like the Apollo Gem or the Optimmersion, you can store the energy you are generating in your immersion tank or your storage heaters for use later in the day. They are far cheaper than batteries and if used effectively can save you just as much energy as batteries can. This should be one of your first options before considering a more expensive battery system.
Manage Supply or Demand
By far the cheapest option is going to be managing your demand for electricity. By trying to use your appliances during the middle of the day, you will save considerably over the course of a year. Storing energy is always going to more expensive and I would advise against it in most cases.
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