It started so innocuously.

At the end of July, one of my roommates in the townhouse we rent in the D.C. suburbs pointed out that while we had the thermostat set to 74 degrees, the house was 78. Oh well, I thought. If the A.C. is barely kicking on, maybe we’ll have a smaller energy bill at least.

For all of August, our house hovered around 78 or 79, no matter how low we set the thermostat. While it was a little too warm for comfort, turning a fan on made it manageable, and we didn’t want to bother our landlord by asking for a repair.

That is until I got our August electricity bill. Normally around $100 a month, in August it was almost $650. Our monthly kWh had gone from 827 to 4,966. What happened?

Turns out, a number of things can go wrong with an HVAC unit making it unable to reach the desired temperature – while the unit is still working long and hard to try and cool down. While setting your thermostat to 78 degrees on purpose might be good for your energy savings, when it’s 78 but trying to cool the house to 70, you are going to end up using a ton of energy while still sitting in the heat. A lesson I learned the hard way.

So how can you not be like me? Here are a few ways to avoid an unexpected utility bill.

1. Sign up for energy alerts.

Most utilities offer an alert system that can warn you about an impending higher bill. These alerts can work a few different ways. For customers with smart meters, which automatically send energy usage data back to the utility, you may be able to set a daily energy use threshold. If your energy use for the day exceeds the threshold you set, you’ll receive an alert telling you that. This is an option I was able to take advantage of through my utility: I set my threshold to 40kwh per day, and anytime the house exceeds that, I receive an email notice. Seeing as our daily kWh was around 160 the month our HVAC broke, we would have known far in advance that something was wrong.

Even for customers without smart meters, your utility might offer alerts based on your billing history and weather patterns – for example, if temperatures are expected to be above average, the utility might send you a warning that based on past months’ data, your bills are expected to be 20% higher.

2. Get fixin’ to fix it.

Another way to avoid an unexpected bill, especially if you can’t sign up for live alerts with a smart meter, is to immediately address equipment problems when you notice them. In our case, we should have contacted our landlord as soon as we noticed the HVAC couldn’t keep up with our thermostat. Maybe you notice the toilet keeps running long after it has been flushed. Or your fridge isn’t staying as cold as it should be. Or the cycle on your dishwasher is taking longer than usual. These can all be indicators that something has gone wrong with the appliance that is making it operate less efficiently, potentially leading to an unusually high utility bill and producing needless pollution. Don’t delay: get it fixed today.

3. Perform regular maintenance.

You might be able to prevent appliances from breaking at all with a regular maintenance routine. Check user manuals on your household appliances for recommended servicing – and if you’re a renter, check your lease agreement or with your landlord to make it clear who is responsible for what maintenance. A few tasks to add to your list include:

• Check the filter in your HVAC system every month, and replace it at least every three months. This can save you up to 15% on heating and cooling costs.
• If you have an older fridge model, make sure to regularly clean the condenser coils – dirty coils could raise your fridge bill by 35%.
• Clean your dryer exhaust at least every year to improve efficiency and prevent dryer fires.

These tips can go a long way toward preventing sticker shock at the end of the month. And as always, keep in mind these seasonal energy efficiency tips that can help you save every day. Nobody should have to pay like you’re running an ice skating rink out of your basement while sitting in a sauna – so learn from my mistakes and save away.