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Everything you need to know about solar panel batteries

Elon Musk has made a Gigafactory, but what exactly is it churning out? Everything you need to know about solar panel battery storage in 5 minutes or less!

Do I need batteries for my solar panels?

Most home solar panel systems generate more electricity on a sunny day than is used, creating an excess of electrical energy. If the excess energy isn’t used or stored, it’s sent to the grid for use elsewhere - sadly only offering you small returns. Many people therefore feel it’s a better option to store their electricity in a battery for later use.

What is solar panel battery storage?

Battery storage is particularly useful for solar energy because of course electricity isn’t generated at night, even though that’s when many of us use more power at home. Fortunately, any excess electrical energy generated by your solar panels can be converted into chemical energy and stored in a battery. The energy in the battery storage can then be converted back into electrical energy when you need it, which prevents your solar panel generated energy from going to waste.

What are solar batteries made from?

Batteries can be made from a number of different materials - traditionally they would have been Lead acid or Nickel-cadmium. However the kind of modern solar batteries we install tend to be made from Lithium-ion, the same technology as laptop batteries and electric vehicle batteries, which can hold significant power in a small space.

What size are solar batteries?

Batteries can vary in size, but the solar panel batteries we install are about the size of a small briefcase and weigh around 25kg.

How many batteries do I need for solar power?

It’s not about how many batteries you need, but at what capacity they’re at, and how much capacity you need depends on how much excess electricity you produce and use. When you book a (free) call with us, we’ll match that up for you, so that you’ll know just what amount of battery storage would suit your needs. You can have a play about it yourself, using our free platform, to get an initial understanding of what your battery storage might be.

How much will solar panel battery storage cost?

When calculating the cost of solar panels, you’ll have to consider whether you want to include a solar battery. The cost will depend on the energy storage that you require, but adding a battery to your system can increase the cost by around £1,000 to £5,000. Most of the additional cost will come from the solar battery itself, but some come from needing an improved inverter. You see, solar panel systems under 3.6kW (around 10-12 panel systems) will typically have a solar panel inverter cost ranging from £500 - £1500, with the inverters on the more expensive side of the spectrum being what you need if you have a battery. Systems larger than this can require a somewhat more expensive inverter, but your Guru will be happy to discuss this in greater detail.

What does an inverter do?

The inverter is what converts the energy from your solar panels into usable electricity. If you’re thinking of getting a system with just panels for now and are thinking of adding a battery in the future, it might be worth getting an inverter that is compatible with batteries now to avoid the cost of having to replace it later. In essence, your system would be “battery-ready”. Whilst solar panels have stabilised in price, battery technology is likely to change a lot in the next 5 years, so being battery ready allows you to take advantage of any future developments in battery technology.

Are solar panel batteries worth it?

Whilst there is an additional cost, there are plenty of benefits. If you use most of your energy in the evening, i.e. when the sun isn't shining and you aren't producing solar energy, a battery can help store the excess energy from daylight hours for you to use in the evening. This helps to reduce your reliance on the grid and stops you from having to buy as much energy. If, however, you use most of your electricity during the day, when the panels are producing electricity, it may not be worth it.

How do I know if a solar battery is the right fit for me?

When using our free and impartial tool, you’ll be asked to select a “usage profile” which describes how you use energy. We then map this against what would be produced by your solar panel system, which will look something like this:

Coverage without a battery
Coverage without a battery
Coverage with a battery
Coverage with a battery

This is a MakeMyHouseGreen usage profile featuring a house with fairly constant usage throughout the day, with small peaks in the morning and evening. The household generates 4025kWh per year with its 10 solar panels facing south. Without the battery, the household uses only 40% of the generated electricity, with the rest being sold to the grid. Adding a 7.2kWh battery means the household is able to use 74% of what it generates.

To see the effect a battery would have on your usage, tick the box on the right-hand side, under the System tab when using our platform. Toggle this on and off to see the change.

If you are considering a system that will produce excess energy during the day, a battery may be a good way to capture that value. However, if you have an electric vehicle that is parked at home during the day and/or can heat your water with your solar panels, then the need for a battery may be less strong. Discuss these options with your Green Homes Guru to see what might be most useful for you and your house. Don’t yet have a Guru to ask? Book a free call by going through the MakeMyHouseGreen platform here.

Will my solar battery system power me in a power cut?

No, unfortunately your solar battery system can't power you in a power cut.

Should I get an extended warranty for my solar power battery?

Like solar panels, batteries come with warranties which are usually between 5-15 years. As with solar panels, the low number of moving parts means that any faults will likely come to light well within the warranty period. Check the average lifespan of the battery you are considering - a quick google search for the name of it and "average lifespan" should help you work out if it's likely to need replacing within either the normal or extended warranty (if offered).

We hear that people who opt for extended warranties enjoy great peace of mind in the eventually that something goes wrong with the kit.

Now that you've completed our battery storage masterclass, you should be in a much better position to make the right choice for your system. We cover more about other system aspects in other articles, but if you have any questions in the meantime, check out our Guru FAQS or drop us an email via team@makemyhousegreen.com.

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