When you’re living off-grid or in the middle of a power outage, it can be tough to keep warm.
With your normal source of heat extinguished, you will be quick to turn to your space heater for warmth.
To run a heater you’ll need a power inverter to convert your stored energy from DC to AC electricity.
But you’ve got to be careful as heaters can use a lot of power so it’s crucial to know what size inverter you need to run a heater.
Even a small portable space heater can draw thousands of watts!
But I won’t leave you out in the cold, together we’ll go through inverter size, best products, and all the other questions you have about using an inverter to run a space heater.
What Size Inverter for a Heater?
You will need at least a 2000 watt inverter, or even bigger, to run a domestic space heater.
This is because the average heater uses between 1500 and 2000 watts.
To know what size inverter you need, you should check the wattage of your heater and add 20%. This is the minimum amount of inverter power capacity you need as inverters are not 100% efficient. An inverter loses energy during the conversion of DC to AC plus needs power to run internal systems like cooling fans.
For example, you would not be able to run a 1500W heater with a 1500W inverter. You would actually need an 1800W inverter to run a 1500W heater.
To work out inverter size, simply multiply your heater wattage by 1.2. So 1500W x 1.2 = 1800W inverter size.
How Many Watts is My Heater?
So now you’ll be wondering how to find out how many watts your heater uses…
The good news is that most space heaters have their wattage listed in the product title or size. You should also be able to find running wattage in the technical specification, user manual, or on a sticker on the appliance like this:
If you can’t find any power consumption details, you could use a wattmeter instead. These are amazing little devices to get a live power reading on any appliance. Very handy if you use a power inverter!
You should expect most heaters to use between 1500 – 2500 watts. Although you can get some lower powered options and devices with eco-modes to reduce consumption. Just remember, a lower watt heater will generate less heat.
Does a Space Heater Need a Pure Sine Wave Inverter?
You don’t need a pure sine wave inverter to run a heater, you should be able to use a cheaper modified sine wave inverter.
Heaters are resistive loads that will cope with the sharp voltage steps of modified sine wave. Plus most have mechanical controls so there are no sensitive electronics. Although, if you have a hi-tech space heater pure sine wave will be needed if it has digital controls or clocks.
Personally, I always like to opt for a pure sine wave inverter as they deliver a more efficient smooth power output that replicates the electricity you get from the mains grid. This means you will never be restricted on what appliances you can run.
Can I Use an Inverter to Run a Heater in the Car?
It might be tough to use an inverter to run a heater in your car. You won’t be able to plug your inverter into your 12V DC cigarette lighter port to run a heater. This is because these ports can only offer 150 watts to your inverter. Even a big inverter could only draw 150W from a cigarette lighter port.
To stand any chance, you would have to hook up directly to your car battery. This would allow your inverter to draw more power. Before doing this check the power of your alternator, as it can range from 500 to 2500 watts. Your alternator is what charges your battery from the engine. If it produces less power than your heater you will eventually deplete your battery. This is because you are using more energy than your alternator can replace in the battery.
If you do run a heater from an inverter in your car, be sure to always run the engine! If you do this without the engine running it will very quickly deplete your starter battery leaving you stranded and with damage to your battery.
How Long Will an Inverter Power a Heater?
Heaters are very energy-hungry devices, just like anything with a heating element. You will draw a lot of amps using a heater from a 12 volt source like a battery. You will likely use between 150 – 200 amps an hour (Ah) with a space heater and 12V inverter.
The length of time an inverter can run depends on the size of your battery and the energy usage of your heater.
It can be a little confusing to work out, so here’s a simple formula (including the inverter efficiency) to work out runtime using battery capacity and heater wattage on a 12V battery/inverter.
(10 x battery capacity in Ah) divided by heater wattage = runtime.
For example, let’s say you have a 200Ah battery and a 2000W heater on a 12V inverter.
(10 x 200Ah) ÷ 2000W = 1 hour.
So 200Ah of battery capacity can run a 2000 watt heater for a maximum of 1 hour.
As you can see, to run a heater for long periods you will need serious battery capacity or electric hookup.
Final Words on Power Inverters for Heaters
Well, there you have it, the crucial information of using an inverter to run a heater.
To be honest, you’ll need a lot of power! At least a 2000W inverter, if not 3000W.
This is because a space heater will use between 1500 and 2500 watts depending on its size. Although, you could look for a low wattage option, but these won’t generate as much heat.
Plus remember, a setup like this will use a lot of energy so be prepared with plenty of large deep cycle batteries, solar power, or other electricity source to run your equipment for long enough.
