Degree Days

Degree Days

Weather Data for Energy Saving

Degree Pro – The Website You Know and Love, Enhanced for Full Professional Use

Degree exists to help people monitor, manage, and reduce building energy consumption. The free website is designed to be enough for basic needs, providing up to 36 months' worth of recent data history, 5-year averages, and a regression tool that works well for relatively small amounts of recent energy-usage data. Degree Pro provides a more comprehensive service to the energy professionals who value the additional data, flexibility, and timesaving it enables.

Degree Pro is a premium version of our website that offers extended historical data and allows larger sets of energy data to be run through the regression tool. Higher-level plans also provide more control over data specification, access to hourly temperature data, and a huge increase in data-generation speed.

On the surface the Pro website looks just like the free website you're used to... But on the inside it's supercharged:

Extended historical data and 10- or 20-year averages

With the Pro website you can generate larger sets of data, going further back in time. The amount available varies from weather station to weather station, but most locations of interest to our visitors have at least one station with data going back to January 2000. This is plenty enough to match most energy-consumption records, and to get 10-year or 20-year averages (covering a much longer history than the 5-year averages that the free website provides).

Generally speaking, most large cities in North America, Europe, and Australia have one or more high-quality airport stations with data going back to January 2000. Major cities in Central and South America and Asia generally have stations with long histories too, though coverage is more patchy in Africa.

Bars and stars

It's easy to check how much data is available for any specific location: Just search on the website (you can do this with or without Degree Pro) until you see a list of weather stations with bars and stars next to them (as in the screenshot to the left). Hover your mouse over a station with a bar and stars and you should see a popup with more information about how much data can be generated for that station. Try that a few times and you'll quickly see that the blue bars next to each station represent the lengths of data history available. With Degree Pro you can download as much of the available history as you want.

Why does the available history vary? Well, some weather stations are newer than others, and some stations have suffered long periods of downtime that prevent us from providing continuous data going back as far as we would like (our system will only ever provide continuous data i.e. no gaps). But in most cases Degree Pro will enable you to access a lot more data than you can with the free website.

Full use of the regression tool to rapidly model HVAC energy consumption

Regression is at the core of much analysis of heating/cooling energy consumption, and experienced energy professionals tend to quickly see the value in our online regression tool. In seconds it runs a multitude of advanced calculations that just can't realistically be done in Excel, testing your energy data against HDD and CDD in thousands of different base-temperature combinations to find the regression models that give the best statistical fit.

The regression tool is invaluable when:

You can use the regression tool on the free website, but you will likely bump into its limits fairly quickly, especially if you use it often. Degree Pro will enable you to use it much more freely, as you will be able to run larger sets of data through it, and data from longer ago (as far back as extended historical data is available). You will also be able to include extra predictors like occupancy or production data in your regressions.

High-speed data generation (see later) will also be invaluable if you plan to use the regression tool a lot.

Custom data specification (on selected plans)

Pro plans with custom data specification enable you to be more precise about the data you want, and get more data in each download. Instead of selecting HDD or CDD and choosing from a list of available base temperatures, you can type a specification of the exact data you want. You can, for example, specify:

So with this Pro feature you can get HDD and CDD together in the same download, and specify precisely the base temperatures you want. You can even specify base temperatures to 0.1°F or 0.1°C granularity (though realistically 1°F and 0.5°C granularity is usually precise enough).

The usual simple data-specification options are also still there for when you don't need these more advanced options.

Hourly temperature data (on selected plans)

Bars and stars

With the higher-level Pro plans you can download high-quality hourly temperature data for all weather stations with 2 or more stars. (You can also download it for stations with less than 2 stars, but the quality won't be as high.) It is available for the same extended historical periods as degree days.

Just like our degree days, our hourly temperature data is neat, perfectly regular, and free from gaps. This is quite different to the raw temperature data we calculate it from. Real-world weather stations have a variety of reporting schedules, and are never perfectly regular over the long term... We take the messy/irregular temperature data that the weather stations report, and process/interpolate it into regular hourly temperatures that are much easier to work with.

NB Hourly temperature data is important for certain sorts of specialist applications like HVAC system sizing and building simulation, but degree days are still the best choice for most analysis of heating/cooling energy consumption. We calculate our degree days accurately, capturing all the temperature variations that are relevant to heating and cooling, including temperature variations within days and, for stations that report frequently enough, within hours too. Daily/weekly/monthly HDD/CDD figures effectively contain all the detail of hourly temperature data, but in a format that is much better suited to comparison with energy-usage data. Hourly temperature data is not a replacement for degree days, rather it is a specialist extra to be used alongside them.

High-speed access to generate data faster (on selected plans)

Generating degree days in the accurate way we do typically involves churning through many thousands (often millions) of temperature readings. The regression tool does a lot of number crunching too. We have many thousands of users and, with all this data processing, we have to be careful to keep our server costs under control. So the free website is built for efficiency rather than speed, and it takes a long time to generate data.

However, for Pro customers with high-speed access we use intensive concurrent processing to generate the data much faster. This is very useful when you are using the regression tool, as it makes it much easier to try different approaches (like different baseline periods or different weather stations) until you are happy with the results. And it's a great timesaver if you download data frequently. (Though do please note that our desktop app is still the best option for downloading degree days for lots of locations, and, with the "API Standard" option mentioned below, you get Pro website access included.)

In most cases high-speed access will enable you to download your data within a second or two of specifying it, and without any sacrifice in data quality. It's like switching from dial-up to full-fibre broadband!

Instant online access to Degree Pro

Sign up for one of the plans below and you will immediately receive a special, encoded link that will give you instant access to the Pro website:

API Standard Pro Team Pro Solo 1-Site Day Pass
$195/month $75/month $29/month $9
Stations worldwide Stations worldwide Stations worldwide Stations near your chosen site only
Extended historical data* Extended historical data* Extended historical data* Extended historical data*
Full use of regression tool Full use of regression tool Full use of regression tool Full use of regression tool
Custom data specification Custom data specification Custom data specification
Hourly temperature data§ Hourly temperature data§ Hourly temperature data§
High-speed access| High-speed access| High-speed access|
Multiple users Multiple users
Desktop app
Sign up for an API Standard account (or Plus or Premium) to unlock the desktop app and quickly download degree days for lots of locations at once. High-speed Pro website access (with all available features) comes included for use by you and your coworkers. Ongoing high-speed Pro website access for you and your coworkers. Ideal if multiple people within your organization use Degree regularly and can benefit from high-speed access, custom data specification, extended historical data, hourly temperature data, and full use of the regression tool. Ongoing high-speed Pro website access for one person. Ideal if you frequently need extended historical data, or full access to the regression tool, or hourly temperature data, or you use the website enough to benefit from high-speed access and custom data specification. 24 hours of basic Pro website access, starting the moment you complete the checkout, and limited to the first weather station you use after signup (or any within 50 km of it). Ideal for one-off projects like downloading extended historical data for your building, or running a large set of energy data through the regression tool.

*Extended historical data

The free website provides the most recent data only (up to 36 months' worth), and average data covering up to 5 years. With the Pro website you can cover much longer time periods. For many weather stations you can get extended historical data going right back to January 2000, and generate longer averages like 10-year and 20-year averages.

Full use of regression tool

You can use the regression tool with the free website, but only for relatively small sets of recent energy-usage data. With the Pro website you can run the regression tool with larger sets of data, and older data, and you can include extra predictors like occupancy or production figures as well.

Custom data specification

Precise control over the data specification, enabling you to download HDD and/or CDD, in a custom-specified range of base temperatures, all in one convenient spreadsheet. And the usual data-specification options are still there too if you prefer to keep it simple.

§Hourly temperature data

Perfectly-regular hourly temperature data with no gaps. Not a replacement for degree days, but important for certain sorts of specialist analysis and building simulation.

|High-speed access

Calculating accurate degree days and running regressions requires a lot of number crunching. Our website usually spreads the load to help prevent the many thousands of users from overloading the system. This makes it efficient, but slow. However, for Pro customers with high-speed access we use intensive concurrent processing to greatly increase the speed. This is a godsend for people who use the website a lot.

Instant access via secure checkout

We use a popular e-commerce service provider called FastSpring to handle billing for us. The "Start Now" buttons above all lead to FastSpring's secure website where you can enter your credit-card details for instant access to Degree Pro.

FastSpring's payment system accepts Visa, MasterCard, American Express, Discover, and PayPal.

Easy cancellation, any time

You can cancel your account at any time, and without penalty. It only takes a few clicks from your billing control panel (which you can access from the email receipt sent immediately after signup). After cancellation you will not be billed again, and your Pro access will continue running until the end of the month that you've already paid for.

Yearly billing option

Instead of paying monthly, you can optionally pay 12 months in advance once a year. It costs the same overall, but it might be more convenient for your accounting. Click here for yearly billing.

Choosing the right plan for you

For energy consultants doing ad hoc analysis, the Pro Solo or Pro Team plans will typically be best (depending on whether Pro website access is just for you or for your coworkers as well), giving you all available Pro features and the flexibility and timesaving that comes with them. Though if your work volume is very low, and you don't need hourly temperature data, you could just buy a Day Pass for each project.

For multi-site energy managers, the desktop app is ideal for downloading degree days for lots of locations at once. Copy in a list of your site locations and the desktop app will quickly download data for all of them into one big spreadsheet. Following that it will be quick and easy to download fresh data for all your locations each day, week, month, year, or whenever you need it. The desktop app will enable you to get all the degree days you need (provided you give it a sufficiently powerful API account), but you might also want Pro website access for hourly temperature data or detailed regression analysis of individual sites. If you choose the API Standard plan (or Plus or Premium), you'll get Team access to the Pro website included, giving you the best of both worlds. Alternatively, if you don't have many sites, you could use the desktop app with the cheaper API Basic account (which does not include Pro website access), or skip the desktop app altogether and download data manually from the website with a Pro Solo/Team account (you'd still need a lot of clicking but the high-speed access would make it more tolerable).

For single-site energy managers or building owners wanting one-off extended historical data or regression analysis for just one building, the 1-Site Day Pass is probably the best option. Afterwards, the free website will probably be fine for periodically updating your data, but you might want the occasional extra Day Pass for more detailed analysis.

For other one-off projects, remember that the Pro Solo/Team plans and the API plans that power the desktop app can all be cancelled at any time. Immediately after purchase you will receive a payment-receipt email containing a link to your billing control panel via which you can cancel in a couple of clicks, at any time. If you get everything done and cancel within the first month (i.e. before the second billing that comes a month after the first), you'll only pay for that first month. Choose the desktop app for bulk data assembly (degree days for lots of locations at once) and the Pro Solo/Team plans for anything requiring more-detailed location-by-location analysis. For projects requiring both, power the desktop app with an API Standard account (or Plus or Premium) and you'll get Pro website access included for free.

Account limits

The server costs associated with generating large sets of data and running regressions can quickly add up, especially for accounts with high-speed access. So we have to put some limits on usage. You are, however, unlikely to hit them unless you are:

If your account has high-speed access, and sees abnormally heavy usage, the first thing you will notice is that the high-speed access will shut off and data generation will become a lot slower. The website will make this clear, and high-speed access will switch back on eventually when the usage has subsided.

If abnormally heavy usage persists, and your Pro website access gets cut off, it is almost certainly because your special encoded link for Degree Pro escaped and too many people were using it. Don't worry though, just email us and we can send you a new replacement link to use instead.

Need extended historical data but can't pay?

If you need to generate extended historical data, and you're unable to pay, we might be able to help you out if you're a cash-strapped charity or a student doing academic research. Please feel free to email us at to tell us more about your project. Otherwise we hope to welcome you as a Pro customer soon!

Already signed up?

The system should have given you a special link immediately after you completed the checkout, and in an email sent at the same time. Find that email (checking your spam folder if necessary), and click the special link. It will take you to our website, but you should see your name at the top of the screen, and you should be able to access all the extra features that your Pro plan offers.

If you click the special link but you can't see your name at the top of the screen, it's probably because your Pro account has expired. Please email us at if you need help!

Choose Your Plan and Get Pro Access Now!

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