Solar power and electric cars go together like peanut butter and jam, fish and chips, or even bacon and eggs. You can happily run an electric car without installing solar panels on your house, but if you combine the two, you’re into an entire world of potential energy and cost savings, and versatility. And the odd thing is that, generally, most people won’t actually charge their EV directly from the solar panels…
The secret to a good relationship between your electric car and solar panels is to have a few other things in place as well. Obviously, a space in front or behind your house where you can park and charge the car almost goes without saying, but a smart electricity meter is also a necessity to make this all work, along with both an electric car and a home charger which can cope with bi-directional power flows. Lots of new EVs can manage vehicle-to-load (V2L) charging and a good smart charger will be able to do that too.
It’s all about the battery
The other good addition to all this — and a way of really future-proofing your home — is to add in a storage battery. Now, this doesn’t need to be massive, somewhere between 5kWh and 10kWh will usually be plenty, and it’s best to go, where possible, for a lithium-iron-phosphate battery as that’s the most stable and reliable battery chemistry for this kind of application.
Will all this be costly? Yes, up front it can be. Adding around 20 square metres of solar panels to your house will cost between €6,000 and €9,000 even once you’ve factored in the grant from the Sustainable Energy Authority of Ireland (SEAI) which is worth up to €1,800. A storage battery will be another €3,000 to €8,000 on top of that. However, it’s estimated that you’ll be quids-in within as little as eight years depending on the installation and the cost.
Don’t charge the EV using solar power
So, here’s how to make the best use of solar panels for your EV. Don’t charge your EV with your solar panels. It’s actually kind of obvious when you think about it. Most of us use our cars during the day, often for commuting to and from work, and so our cars aren’t going to be at home when the solar panels are producing their maximum yield of energy. Equally, most of us will charge our electric cars overnight, on the cheapest possible electricity rates, when it’s dark and there is no solar power.
So how does solar power help? Well, a standard 20-square-metre solar panel installation in Ireland will generate around 2,600kWh of energy over the course of a year, which the SEAI estimates is around 40 per cent of the power an average family home uses in that time. Which is great — you’re now getting almost half of your electricity from sunlight. The real trick here is the storage battery.
You see, during the day when it’s bright (it doesn’t have to be massively sunny) you should find that your solar panels produce more energy than your house is using. So the ideal thing to do is to use that energy first to top-up your storage battery, and after that any excess power over and above the household usage rate can be sold back to the national grid.
Up to €400 tax-free
Under the current rules, you’re allowed to make €400 from the grid for exported electricity from your solar panels before you have to pay any tax on it. Keep that number in mind for a moment…
Now, when you come home from work, you’ll be hitting peak electricity usage time, when everyone turns on their kettles, cookers and televisions, and when electricity is at its most expensive. Here’s when your storage battery swings into action, as, if it’s been topped up during the day, it should be able to provide all or most of the electricity you need at peak times, which will put a dramatic dent in your bill.
Now comes the electric car charging. Generally speaking, on most Irish electricity tariffs, you’ll want to leave charging until around 11pm, when the night-time rates kick in (this will vary from provider to provider so make sure you shop around for the tariff that suits you best) and there are some chargers that can actually detect when electricity is at its cheapest rate and start charging automatically.
Dramatically reduced EV running costs
Now, obviously everyone’s electric car, and its usage, and their charging habits will differ, but we estimate that running an average-sized electric family hatchback — such as an MG4 EV or a Renault Megane E-Tech — for the average 16,000km mileage that Irish drivers cover each year will cost in the region of €450. That’s assuming most of your charging is done at home, on cheaper night rates, and it allows for a little (much more expensive) DC public charging for longer journeys.
Remember that €400 you’ve just earned from selling solar power to the grid? Well, there you go. Your solar panels have just cut your EV running costs down to a mere €50, less than the price of half a tank of petrol for most cars right now, for an entire year. And the solar panels never actually charged the car directly.
In fact, it’s this ultra-cheap running cost that makes the mixture of solar panels and electric cars so tempting. Yes, solar panels and storage batteries are expensive to get installed but remember that an average family hatchback with a petrol engine costs around €1,700 a year just in fuel. If you can cut that €1,700 to €50 — as is entirely possible — then think how quickly you’ll claw back that solar panel installation cost.