Here’s what our electricity use looked like on Saturday. It was mostly sunny, with plenty of solar power generated during the day. There’s an early spike of energy use at breakfast, the washing machine running midday, and then the biggest use of energy is to cook dinner. In these northerly lattitudes in winter, that’s after the sun has gone down.
Our house will produce more energy than we use over the course of the year, but we’re still buying it in from the grid.
To get the most out of our solar power, we need to be able to use more energy when the sun shines. Here are five ways we could do that.
1. Get a battery. The obvious choice: a domestic battery charges up on the solar power and discharges at night or when the sun goes behind the clouds. Even a small one would run the house and the fridge overnight. It would use more of the solar, but it wouldn’t necessarily save money at this point. Some research suggests that since batteries lose capacity over time, it might never break even. This will change as batteries get cheaper, and there are more options on the market every month. For us it’s a matter of when, rather than if.
2. Hot water. Homes that have a hot water tank can divert excess solar power into water heating with relative ease, with an Immersun system or similar. The energy is stored as heat, using excess solar to offset gas costs. We don’t have a hot water tank, so we’d have to turn to the more unusual technology of a thermal battery. Sunamp is the only domestic supplier I’m aware of in the UK. Their unit stores heat in a phase change chemical, connecting to the boiler and providing pre-heated water. If anyone’s had any experience of them, I’d be interested to hear about it.
3. Charge an EV. Solar panels and EVs were meant for each other, except that many people will only be able to plug their cars in at night. If you are able to plug it in during the day, it can trickle charge from the solar. The Zappi charger can do this, diverting excess power to the car in a similar fashion to the hot water systems. You’ll be running the car on free power, and it’s cheaper to charge the battery you already have in the car than fit a separate domestic battery. I haven’t got an electric car, so it’s not one for us just yet.
4. Smart appliances. These have been a long time coming, but the theory is sound: if appliances in the house could communicate with the solar inverter, things could run or charge automatically when power is available. The fridge and freezer could choose when to run the cooling cycle. Laptop and phone chargers could switch off or on as required. The washing machine would wait for the sun to come out. There are a variety of smart home systems on the market, of varying degrees of complexity and most of them aimed at convenience rather than energy saving. I haven’t seen a system we can use just yet and I reckon the industry needs to standardise before things will really work, but I imagine it’s a matter of time before we can do this.
5. The low tech approach. Until all these new technologies are available and affordable, there are plenty of perfectly serviceable workarounds. The slow cooker is a good one, if you can get things started early and leave meals cooking on the solar through the day. When I’m working from home I boil water in the middle of the day and stick it in Thermos flasks to use later. The bread machine can be programmed for specific times. Simple appliances such as the slow cooker or a dryer can run on plugs with timers. I unplug my laptop at night, and charge phones from a power pack that charges during peak sunlight. Some of these are more involved than others, and not everyone has the freelancer’s luxury of being able to potter about all day switching things on and off.
Of course, what’s going on with my own solar system is repeated up and down the country, with solar power hitting peak production at periods of low electricity demand. How to use more of our solar power is a national energy conversation as well as a domestic one. We need more storage on the grid – dropping VAT on batteries might be a simple policy to give things a boost in Britain. We need more heating and hot water served by renewable energy rather than gas. All of these are all the more important with the withdrawal of feed in tariffs this year.