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Choosing an Off Grid Inverter

How to Choose the Right DC to AC 230V Power Inverter

What is a power inverter?

First of all, let’s start with the definition. What is a power inverter?

A power inverter is a device which converts battery power into mains power, i.e. it transforms 12V direct current (DC) into 230V alternating current (AC).

230V AC is the power supplied to our houses by utility companies, and this is the power required by most normal household appliances such as lights, TVs, fridges etc.

There are two main types of inverters:

  • Off-grid inverters, which work as a standalone system and require batteries (typically used in caravans, cars, boats or locations without access to mains power)
  • On-grid or grid tie inverters, which require mains power to work (typically used in household solar systems and take input directly from solar panels)

We are going focus on off-grid inverters only – i.e. inverters which can be used to build an off-grid 230V solar system.

Which power inverter should I choose?

So, which off-grid inverter is best for your battery / battery bank in a caravan, motorhome, boat or for a standalone off-grid solar system?

In order to answer this question, you will need to consider three key points:

  • Type of inverterModified sine wave / Pure sine wave
  • Power rating (wattage) of the inverter
  • Input voltage (specifically in the case of a standalone solar system)

Types of inverter – modified sine wave vs. pure sine wave inverters

The type of power inverter you should choose depends on the type of power output you require. Pure sine wave inverters provide an output which follows a sine wave harmonically. This is similar to utility-supplied grid power. Although modified sine wave inverters can work well with many appliances including light bulbs, mobile phone chargers and office equipment, if your budget allows, we would always recommend buying a pure sine wave inverter.

Determining the power rating of your inverter

If you need to power small appliances such as a mobile phone charger or energy efficient light bulbs, you don’t really need to buy a 2000W power inverter because it will consume significantly more power (even in standby mode) and work very inefficiently with small appliances. On the other hand, if you connect a coffee machine to a 150W inverter you will quickly blow a fuse (if not the inverter itself). Therefore the power rating of the inverter should be chosen based on the power consumption of your load. The following table contains the typical power consumption of some standard household appliances and the recommended inverter rating.

Equipment Power consumption Continuous power rating of inverter
300W 600W 1000W 1500W 2000W 3000W 4000W 6000W
— Home and kitchen appliances —
 Table fan* 50W Ok Ok Ok Ok Ok Ok Ok Ok
 Sewing machine* 100W Ok Ok Ok Ok Ok Ok Ok Ok
 Halogen light** 100W Ok Ok Ok Ok Ok Ok Ok
 Pedestal fan* 100W Ok Ok Ok Ok Ok Ok Ok Ok
 Blender* 350W  – Ok Ok Ok Ok Ok Ok
 Small fridge* 200W Ok Ok Ok Ok Ok Ok Ok
 Large fridge* 500W Ok Ok Ok Ok Ok
 Washing machine (no heating)* 700W Ok Ok Ok Ok
 Microwave oven** 900W Ok Ok Ok Ok Ok
 Coffee maker* 1200W  – Ok Ok Ok Ok
 Iron 1500W  – Ok Ok Ok Ok
 Hair dryer* 1200W  – Ok Ok Ok Ok
 Toaster 1200W Ok Ok Ok Ok Ok
 Vacuum cleaner* 2000W Ok Ok Ok
 Dishwasher* 1500W Ok Ok Ok Ok
 Hob 1500W Ok Ok Ok Ok
 Washing machine (with heating)* 2000W Ok Ok Ok
 Air conditioner* 3000W Ok Ok
 Electric oven 5000W Ok
Continuous power rating of inverter
— Audio and video appliances — 300W 600W 1000W 1500W 2000W 3000W 4000W 6000W
 12” colour LCD TV 20W Ok Ok Ok Ok Ok Ok Ok Ok
 Satellite TV receiver 30W Ok Ok Ok Ok Ok Ok Ok Ok
 HiFi stereo with CD changer** 50W Ok Ok Ok Ok Ok Ok Ok Ok
 DVD / Blu-ray player 50W Ok Ok Ok Ok Ok Ok Ok Ok
 20” colour LCD TV 100W Ok Ok Ok Ok Ok Ok Ok Ok
 42” colour LCD TV 200W Ok Ok Ok Ok Ok Ok Ok Ok
 100W stereo amplifier** 200W Ok Ok Ok Ok Ok Ok Ok
 Home theatre system** 500W Ok Ok Ok Ok Ok Ok
 Active speaker 250W RMS** 500W Ok Ok Ok Ok Ok
 Active speaker 500W RMS** 1000W Ok Ok Ok
Continuous power rating of inverter
  — Computers and home office — 300W 600W 1000W 1500W 2000W 3000W 4000W  6000W
 Mobile phone charger 5W Ok Ok Ok Ok Ok Ok Ok Ok
 Small inkjet printer 40W Ok Ok Ok Ok Ok Ok Ok Ok
 Laptop 50W Ok Ok Ok Ok Ok Ok Ok Ok
 Fax machine 50W Ok Ok Ok Ok Ok Ok Ok Ok
 Desk lamp 50W Ok Ok Ok Ok Ok Ok Ok Ok
 Desktop computer with 17” monitor 400W Ok Ok Ok Ok Ok Ok Ok
 Large laser printer* 800W Ok Ok Ok Ok Ok
Continuous power rating of inverter   
— Power tools and other equipment — 300W 600W 1000W 1500W 2000W 3000W 4000W 6000W
 Drill* 800W  – Ok Ok Ok Ok
 Electric chainsaw* 1000W  – Ok Ok Ok Ok
 Electric lawn mover* 1000W Ok Ok Ok
 Pressure washer* 1000W Ok Ok Ok
 Grinder* 2000W Ok Ok Ok
 Air compressor* 2000W Ok Ok Ok

*Appliances marked with a star are likely to have a starting power consumption several times greater than their normal working power (typically this is caused by electric motors). This should be taken into account when choosing the correct size of inverter. For example, even though electric lawn mowers have a normal working power of 1000W, their starting power is over 4000W. This means that an inverter with a continuous power of 2000W is not suitable, because its peak power is limited to only 4000W. Always take into account the starting power requirements of your equipment – especially devices with electric motors – when choosing the right inverter.

**These appliances do not have an electric motor inside, but still have a variable power consumption with power spikes. Therefore they require a larger inverter than would be needed for other appliances with a similar nominal power rating.

Please also note: this table is provided for general guidance only. The actual power consumption of your appliances, as well as starting power requirements, may vary considerably. In all cases you will need to check the specifications of your equipment to find their continuous and starting power requirements. If more than one device is connected to the inverter, the total power consumption should be the sum of all appliances used. This will determine the total inverter power required.

Determining the input voltage of your inverter: 12V or 24V

If you are looking for an inverter for your 12V leisure battery in a motorhome, caravan or boat, there isn’t much choice in terms of the input voltage – you will need a 12V to 230V inverter, because your battery is 12V. However, if you are building a standalone off-grid solar system (e.g. in a house, garden, shed or farm), then you can choose the voltage of your battery bank, and consequently, the input voltage of the inverter.

Instead of a 12V battery bank, you may choose to build a 24V battery bank (2 x 12V batteries wired in series will produce 24V). In this case you can use a 24V DC to 230V AC inverter, rather than 12V DC to 230V AC. This set-up will provide some important benefits:

  • The input current for the inverter will be two times smaller for 24V than for 12V, making the inverter and the entire system safer and more reliable
  • The cables between your battery and the inverter do not have to be as thick as those used for a 12V battery bank and inverter.

This is particularly important for large standalone solar systems with 2000W inverters. For such power levels, our recommendation is to opt for a 24V battery bank and an inverter with a 24V input voltage.

If in doubt please ask, we are happy to help or if you would like to see our current selection of off-grid inverters click here 

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