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The Next Million Powerwall Rebate - you can get up to £750 back for your Tesla Powerwall installation: Find out more
If you’ve been given a quote for a home battery, you’ve probably seen a datasheet full of facts and figures. For those new to the world of solar and battery storage, this can be confusing.
This guide breaks down everything in plain English, so you can understand what those numbers actually mean, and why Tesla is very different to other systems, such as those from Sigenergy.
A home battery stores electricity so you can use it later, instead of buying it from the grid.
That electricity could come from your solar panels during the day, or from cheaper off-peak electricity overnight. The goal is simple: to use more of your own energy and rely less on the grid.
Start with the basics: kW vs kWh
These are two of the most important numbers you’ll see.
The Tesla Powerwall 3 has a storage capacity of 13.5kWh. This tells you how much energy it can hold.
Think of it like a water tank. The bigger the number, the more energy you can store for later.
In real terms, this is usually enough to run a typical home through the evening and overnight, depending on your usage.
Tesla Powerwall 3 has an inverter than can deliver up to 11.04kW. This tells you how much power it can supply at once.
If we go back to the water tank analogy, think of the size of the pipe connected to the tank. The bigger the pipe, the more water that can flow through at once.
This is important as modern homes often use lots of power at the same time: cooking, kettles, showers, and heating all add up quickly. Many systems are limited to 3.6kW or 6kW, which can restrict what you can run from the battery at one time.
The inverter is one of the most important parts of your system, but it’s rarely explained properly.
Your solar panels and battery store electricity as DC power, but your home uses AC power.
The inverter converts that stored or generated electricity into a form your home can actually use. In simple terms, it’s the engine of your energy system. It controls how much solar you can generate, how quickly your battery charges, and how much power you can use in your home at once.
The Tesla Powerwall 3 includes a powerful, built-in 11.04kW inverter, which is a big advantage over systems that rely on smaller or separate units.
This is one of the most overlooked parts of any quote. Your solar panels may be capable of producing a lot of electricity, but your inverter controls how much of that you can actually use.
Solar panels generate DC electricity. The inverter converts it into usable AC electricity for your home and battery. If your inverter is too small, it will limit how much solar energy you can use, even if your panels could produce more.
The Tesla Powerwall 3 offers inverter outputs up to 11.04kW, which is much higher than many alternatives. This means:
With smaller inverters, you are more likely to hit limits.
Clipping is when your solar panels are producing more electricity than your inverter can handle. When that happens, the extra energy is simply lost.
For example, if your panels are producing 5kW but your inverter can only handle 3.6kW, the remaining energy is wasted. Over time, this can lead to a significant loss of free electricity. A larger inverter, like Tesla’s, reduces this issue.
The Tesla Powerwall 3 has three MPPTs. MPPT stands for Maximum Power Point Tracker. Each MPPT allows a group of solar panels to work as efficiently as possible, even if they are on different parts of your roof.
Three MPPTs means that solar panels on the front, back and an extension can all perform independently. Many other systems only have two MPPTs, which can reduce your overall generation and flexibility.
Energy retention tells you how efficient your battery is. When you store electricity, some of it will be lost. The energy retention figure tells you how much you actually get back.
Tesla Powerwall 3 retains around 80% of stored energy. So, if you store 10 units, you get about 8 back to use. Many other systems only return 6 or 7 units, which leads to more wasted energy over time.
Depth of discharge tells you how much of the battery you’re allowed to use. Tesla Powerwall 3 allows for 100% usage. This means all 13.5kWh is available to you.
Other systems are often limited to around 95%, meaning some of your battery storage is always unavailable.
A charge cycle is one full use of the battery. Many manufacturers limit how many battery cycles you can use over the lifetime of the system. Some, such as Sig, even reduce this if you use smart or Ai features.
Tesla allows unlimited cycles during the 10-year warranty period, and includes its smart energy software as standard, with no extra cost and no impact on your warranty.
Batteries are affected by temperature. The Tesla Powerwall 3 operates between -20°C and 50°C, and features built-in heating at cell level.
Many other systems only operate efficiently between 0°C and 30°C, which can lead to reduced performance in more colder (or hotter) conditions.
IP ratings tell you how well the battery is protected from dust and water.
Tesla Powerwall 3 is rated IP67. This means it’s fully sealed against dust, and can even handle being submerged in water.
Many other systems are rated IP65, which offers less protection, especially against water.
Tesla Powerwall 3 can be installed on a wall or on the floor, giving you flexibility depending on your available space.
Many other systems must be floor mounted, which can be more restrictive.
Tesla includes built-in connectivity via a SIM card, with no ongoing charges. Some other manufacturers charge for connectivity or advanced features, which can add to your long term costs (and reduce your system payback).
Tesla provides a full 10-year warranty across the entire system. This includes the battery, inverter, gateway, and all other components.
Many other systems split their warranties. You might get 10 years on the battery, but only 5 years on other parts, and as little as 2 years on certain components. As a comparison, Sig have a 10 year warranty on their batteries, but only 5 years on the gateway, and 2 years on some other parts such as battery casing.
Tesla have been producing home battery systems for over 10 years, and is one of the largest inverter manufacturers globally. If something goes wrong, they will replace parts with new components at no cost to the customer.
Some newer manufacturers have only been in the UK market for a few years, and there have already been reports of recalls and issues.
Yes, with the Tesla Powerwall 3, you can add more batteries (expansion packs) at any time. Each new battery comes with its own full 10 year warranty, giving you flexibility as your energy needs grow.
When you understand what all the figures mean, comparing systems becomes much clearer.
It comes down to:
The Tesla Powerwall 3 performs strongly across all of these areas, which is why it often delivers better long-term value than alternatives.
Many systems look similar on a quote, but once you understand the details, the differences are clear.
Choosing the right battery is about more than just upfront cost. It’s about how much energy you will actually use, how reliable the system is, and whether it will still be performing properly in ten years.
If you want help comparing quotes in plain English, we can help you ensure you’re choosing a system that genuinely works for your home.
