Choosing a new thermostat these days is almost as complicated as picking a new cell phone or selecting from a dizzying array of laptops.

That old, round mercury-filled thermostat we all remember from Grandma’s house has been replaced with touchscreen panels and wifi enabled units that can be adjusted no matter where you are.

With so many options, how can you be sure you’re getting a thermostat that you’ll be happy with for years to come?

Before you run out to Lowe’s to grab a new thermostat for your air conditioning and heating system, consider these items:

Your Budget. A basic thermostat starts at about $15, but you can certainly spend a lot more — up to around $250 for a consumer-grade learning thermostat. Before you even start thinking about thermostat features, though, figure out what you’ve got to spend. Those extra dollars turn into extra features, energy-saving options and information displays you may find are worth the price. Remember, a programmable thermostat can last up to 15 years and will save you well more than the additional cost to purchase.

Your Schedule. Programmable and learning thermostats are great for someone who has a regular schedule and works away from home, but these days, that’s not always the norm. Between swing shifts and telecommuting, people are working increasingly non-standard hours. When you’ve not got a 9-to-5, you’ll find yourself fiddling with the controls often to maintain a comfortable climate — so the more precision programming options the better.

Analog thermostats are cheap and don’t have to be reprogrammed every time your schedule changes, though you will have to remember to change the temperature when you come and go. Another option for irregular schedules is a WiFi enabled thermostat that you can turn up and down from anywhere. Seven-day programmables give you more options if your schedule is semi-regular, the 5/2 style programmables are perfect if you are still going to a day job.

Your Space. It may seem like a little thing, but the size of the thermostat matters, too. After all, there are probably holes in the wall from the thermostats from HVACs past or other spatial concerns. Modern thermostats range in size considerably, from the Nest, at slightly over 3 inches in diameter, to Honeywell’s enormous 5 inch by 6.25 inch basic Wifi thermostat.

Your Thermostat Wiring. Even if you’ve got your heart set on a top of the line WiFi thermostat, it might not be possible with your current HVAC configuration. Those types of units require a lot of juice, so a fire wire system with a dedicated thermostat power line is required to keep one running. Older homes are much more likely to be plagued with four-wire thermostat wires, so unless you want to upgrade your thermostat wire you’ll need to choose a programmable thermostat that needs a regular battery change.

Your Lifestyle. Programmable, WiFi and learning thermostats are great for people on the go — they allow you to keep some control over your home’s temperatures and utility bill without having to constantly make manual changes. Some provide additional features, like weather forecasts and even energy usage reports to help you save even more. However, if you’ve got a lot of people coming and going, keep a steady temperature in your home regardless of the weather or have roommates that tend to override your programs, these extra features may end up just costing you extra money upfront.

What’s the Deal with “Learning” Thermostats?

Learning thermostats have taken the basic concept of a temperature-sensitive switching mechanism for your air conditioner and furnace and turned it on its head. These units may seem very expensive for what they do, but they measure a lot more than a standard thermostat can. Along with learning your temperature preferences based on the input you provide, thermostats like Nest have multiple temperature sensors to get a more accurate temperature reading, a humidity sensor to allow the unit to track moisture in the air (or lack thereof) and are capable of gathering weather data over the WiFi connection.

All of these tools taken together give learning thermostats a way of keeping your home comfort level high, in a way that older models can’t. For example, if the unit has learned that you’re typically home at 6 pm, but it’s a very hot and sunny day, it may start trying to cool your home sooner than it would if the day was overcast to achieve the same result. A programmable thermostat, on the other hand, would start cooling your home at a set time, regardless of the outdoor conditions, potentially wasting a great deal of money in its lifetime.