If you’re considering investing in a solar battery, you’ll want to know how much of your house it can power and for how long.
Fully understanding the capabilities and limitations of battery storage in your home is important. It impacts cost efficiency, energy efficiency and everyday practicality.
The short answer is that a solar storage battery can power a house, but it depends on various factors. This makes the topic a little complex, but we’ll help you understand more.
In truth, the prospect of having all of your energy needs met by solar PVs and a solar battery all year round are unrealistic.
In this article, we’ll explore what you can expect from a solar battery in terms of powering your home and the factors affecting this. We’ll also discuss certain scenarios to give you a clearer picture of expectations.
How does battery storage work in a home?
A home battery storage system consists of several components that work together to store and distribute electrical energy.
The main component is the battery itself. In residential settings, the best type of storage battery is a lithium-ion model due to its high energy density and long lifespan.
The battery is connected to a control box and an inverter, which converts the direct current (DC) electricity stored in the battery to alternating current (AC) electricity that can be used to power household appliances.
In homes with solar panels, the battery will be connected to these so any excess energy generated can be stored.
When the home requires more energy than the solar panels can provide, such as at night or during the winter months, the stored energy is discharged from the battery to power your home appliances.
The battery storage system can also be connected to the national grid. In some cases, homeowners may choose to draw energy from the grid during off-peak hours when electricity rates are lower, storing it in the battery for use during peak hours when rates are higher. This process can help you save money on your energy bills and is one of the many benefits of solar battery storage.
You can also earn money by exporting energy to the grid when your home’s needs are met and your battery storage is full. This usually only happens during long, sunny summer days.
Can battery storage power a house?
So, can battery storage power a whole house?
As we’ve hinted, the answer depends – with solar panels and battery storage, there are lots of different factors at play.
In theory, yes a solar panel can power a house. In practice, a normal sized solar battery is unlikely to discharge enough energy to power your home for a significant amount of time.
A solar battery can provide as much electricity per day as it can store and safely discharge. This is all to do with the battery’s capacity, measured in kilowatt hours (kWh), power and depth of discharge. We’ll discuss these shortly.
In the UK, there aren’t many properties that can rely on solar power to provide all of their energy needs throughout the year. When it’s broken down, the average UK home uses between 6-10kWh of electricity per day.
Let’s take a good sized 10kWh residential solar battery to give you an example.
On its own, this battery can provide more than enough electricity for a standard day in a three-bedroom home. You’ll be able to power your lights, TV, appliance charges, fridge freezer, your dishwasher and perhaps even your washing machine. If you’re lucky you may even get up to two days of use from a fully charged battery.
However, you may come into trouble if you’ve electrified your heating, for example with an air source heat pump, or you want to charge your electric vehicle. These power-hungry appliances will quickly drain your battery, leaving it unable to power your house unless it’s charged up again.
Factors affecting battery storage
There are several factors influencing the ability of a battery storage system to power a house effectively. Let’s take a look.
Battery capacity and power output
The capacity and power output of a battery are two primary factors in determining how long it can power your home.
Capacity, measured in kWh, represents the total amount of energy a battery can store, while power output, measured in kilowatts (kW), indicates how much energy the battery can deliver at once. The Depth of Discharge (DoD) is how much capacity the battery can discharge without damaging its lifespan.
For example, if your battery has a capacity of 10 kWh, you can in theory power a 5kW appliance for 2 hours or a 1kW appliance for 10 hours. However if the DoD is 80%, the battery will only be able to discharge 8kW before you have to charge it again.
If your area suffered from a power cut, you’d be able to run your home for a few hours, if not a day, from a fully charged medium to large sized battery.
Household energy use
Of course, how long a battery can power a home for all depends on how much energy you’re actually using.
It’s a fairly simple process to calculate how much energy each of your main devices and appliances use. Knowing this will help you determine which devices you can run and for how long.
For example, in isolation a 10 kWh battery can power a:
- 100W TV for 100 hours
- 150W refrigerator for 66 hours
- 10 x 10W light bulbs for 100 hours
- 750W microwave for 13 hours
However, it’s likely you’ll be powering more than one appliance at once. Be mindful that powering lots of smaller appliances at the same time will also drain your battery quite quickly due to the greater number of calculations the control hub has to make.
It’s possible to determine which electrical circuits around your home (as shown on your circuit board) get priority from the storage battery energy.
Seasonal variations
The efficiency of solar PVs and battery storage differs drastically between the summer and winter months.
At the height of summer during a sunny spell, you might be able to go several days without tapping into any mains electricity. You can effectively go off-grid.
This is because your home will be using the electricity generated from the panels during the long days and sending any excess to the battery that’ll be more than ample to cover your night-time energy use. You’ll probably be exporting energy to the grid too.
However, during the winter this isn’t the case. The days are shorter and the angle of the sun is lower. It’s thought that your solar PV array will generate around a quarter of what it can in the summer.
To fully power an electrified home and be independent from the grid, you’d need a much bigger battery.
Firstly, large batteries are expensive. And secondly, this system is likely to be heavily oversized in the summer.
Is battery storage worth it?
Investing in a solar battery can be a smart decision for many homeowners. The main reason is that it allows you to maximise the use of the electricity generated by your solar panels. By storing excess energy during the day and using it later when needed, you can significantly reduce your reliance on the grid and lower your electricity bills. You’ll also be decreasing your environmental footprint.
Storing and using your own solar electricity is often more cost-effective than exporting it to the grid, as compensation rates for exported energy can be low – around four or five times lower than the price you pay to buy electricity.
If you’re in an area prone to power cuts, a solar battery can provide reliable backup, ensuring that your essential appliances and devices continue to work.
However, it’s important to acknowledge that solar batteries aren’t cheap. Costs typically range from £2,500 to £10,000. But by using your stored energy during peak hours or when electricity prices are high, you can begin to offset the initial investment in the battery storage system. The payback period for a solar battery is usually at least five years, but batteries can last between 10-15 years when maintained properly.
If you’re looking for full grid independence, you can achieve this through a solar and battery system, especially during the summer. However it would need to be significantly oversized to make up for the lack of generation during the winter.
Rather than aiming for full energy independence, the vast majority of UK homes use solar PVs and battery storage to reduce their reliance on energy suppliers and lower their bills, whilst becoming greener and helping the environment at the same time.
