Do Block Heaters Use a Lot of Electricity (True Cost)

If you live in a cold climate, you might consider using a block heater on your engine. But do block heaters use a lot of expensive electricity and cost too much to be practical?

If you’re curious about why people install a block heater, consider how much harder an engine has to work to start when it’s bitterly cold. A block heater warms the engine’s coolant and its oil before you start it, cutting down on wear and tear and also making it more likely the engine will turn over and start. 

But do those advantages outweigh the block heater’s consumption of electricity and the corresponding increase in your electric bill?

A few key themes we’ll explore here include:

  • How much electricity block heaters use
  • The cost of electricity for a block heater
  • Ways to cut costs when using a block heater

Keep reading to clarify all your doubts about this topic.

Block heater to a car in the snow

How Much Electricity Do Block Heaters Use?

Block heaters come in a range of sizes. Smaller models are usually around 750 watts, while larger units can be 1500 watts or more. To put that into perspective, consider that running a smaller 750-watt block heater is the equivalent of turning on ten 75-watt light bulbs.  

As the size of the unit increases, the energy consumption will too. 

Block Heater Electricity Costs

As of September, the average price of residential electricity in the USA was 14.19 cents per kilowatt-hour. The price can be quite a bit higher in areas with a colder climate, so you should check your electric bill to see what your own rate is. 

Let’s assume that you’re paying fifteen cents per kilowatt-hour and that you have a 1500 watt block heater. To figure the cost to run it for one hour, you would multiply the wattage by the hourly rate.

But, since we usually measure our appliance’s power consumption in watts, and our electrical costs come as kilowatt-hours (kWh), we have to do a little extra math to display the measurements in the same units. To do so, divide the wattage by 1,000 to convert to kWh. 

1500 watts / 1000 = 1.5 kWh

Now, using the formula of cost per kWh x the wattage of our heater in kWh x the time you want to run it, we can estimate the costs of running a block heater. 

Let’s say you want to run your same 1500 watt heater for 10 hours at the same cost of $.15 per hour. 

1.5 kWh * 10 hours * $.15 = $2.25

If that’s the cost of running your block heater per night, and you have to run it for about half the nights of the year, your annual cost would be $2.25 multiplied by 180. That means you’d be shelling out $405 per year to run one block heater. 

Since many homes have more than one crucial engine, the costs of block heaters can get really high, really fast. For instance, if you have an emergency standby generator, two cars, and a tractor, and they all need block heaters, in our above example, you’d be forking over almost two grand to the electric company every year! 

If that all seems like too much math for you, take advantage of an online calculator tool, where you can plug in your values and determine your estimated electrical usage and costs. 

Cutting Down on Block Heater Costs

Using a block heater is just about mandatory in some areas. It’s just too cold to start an engine without a bit of pre-warming. So while you can’t completely eliminate the cost of running one, you can minimize the expense by using it as efficiently as possible. 

Use a Timer

Let’s say you need your truck ready to run at 0500 hours. Consider installing a timer so that the heater runs from 0230 until 0500, giving it plenty of time to warm your vehicle’s coolant, oil, and engine. By installing that timer, you can cut down dramatically on the consumption of electricity and, in turn, cut your costs. 

For some engines, that might not be practical. For example, if you have a generator system or a vehicle that needs to be ready to go at a moment’s notice, you might need to run the block heater much more often. 

But you still might be able to cycle the system on and off to keep things warm without running it constantly. For residential customers with only a single heater, or maybe two, it’s not going to necessarily break the bank to run a block heater quite a bit. 

But if you have an extensive fleet of vehicles and engines, the costs can become significant quite quickly. Imagine if a police department in Alaska, where electricity costs about $.23 per kWh, needed block heaters for their 30 patrol cars?

Running one of the reserve units’ heaters 24 hours per day would cost more than $8 per day. Even if half the cars are out on the road at any given time, running the remaining fifteen units would cost $120 per day or $3,600 per month. 

Use the Appropriate Setup

If your block heater doesn’t reach a nearby outlet, be careful when you choose your extension cord. Choosing a cord that isn’t thick enough can lead to a situation where either your vehicle isn’t getting the heat it needs, or you damage the block heater itself. Using the wrong size cord can also create a lot of excess heat and set the cord on fire. 

So, minimize the length of the cord you choose as much as possible and use the thickest gauge cord you can find. The manufacturer of your block heater will probably recommend the exact specifications of the extension cords you can use. 

If you can feel heat anywhere along the extension cord while the block heater is running, that means two things: you’re risking an overheated cord, and you’re wasting electrical energy! Wasting energy is never good, but risking a fire is even more dangerous! 


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