Yes. We’re so excited about the new series of Game of Thrones, we’ve decided to combine our geekery for energy with our obsession for all things Westeros and create this: an estimate of the annual heating (or cooling) bills of each castle. We even came up with some inventive renewable alternatives to power them.

To calculate the overall heating bills of each castle in Westeros, we took the following steps:

1. Estimating the size of each castle and city. These were calculated using multiple sources. As a starting point, we looked to a campaign by London & Country, who calculated estimated areas for many of the castles we wanted to look at: The Red Keep, Winterfell, the Great Pyramid, Castle Black, and the Twins.

2. Looking at other areas. We also wanted to look at Sunspear, the castle of House Martell in Dorne, as the Martells are looking to become major players in the new season. After scouring the Westerosi forums, we found comparisons between the size of Sunspear and other ‘medium-sized castles’, including Pyke. Another property service estimated the size of Pyke at 5,500 m2, so we use that as a guide for the size of the Sunspear.

3. Estimating indoor area. We studied maps of each location to estimate the indoor space of each castle that needs actually heating or cooling, as there were a few special considerations. For instance, with the Twins, the bridge connecting the two castles obviously doesn’t need heating. So we worked out the area of the bridge compared to the widest section of the Thames, a comparable river, and the width of the bridge – two wagons, as discussed in the books – and removed its area from the total.

4. Comparing climates. You can’t work out the bills without taking the climate of each kingdom into account. So we looked at the filming locations used in the Game of Thrones series. Winterfell, for instance, was filmed largely in the UK and Ireland, so we can compare it to the climate of the UK. The Red Keep, on the other hand, used locations in Croatia, which is obviously much hotter.

5. Calculating cost to heat/cool per square metre. We used existing research about the cost of heating or cooling a square metre in each individual country – taking climate into account – in order to figure out the cost. You can see the full list here.

6. Calculating the amount of wood needed. Your average hardwood has an energy content of 14.9MJ per kilogram. To work out how much wood we’d need for each castle, we simply converted this to a kWh value. Then divided each castle’s total by this number to get the number of kilograms required.

7. Calculating renewable energy alternatives. We chose an appropriate renewable energy source based on the climate or backstory of each location, eg. Sunspear has solar panels because of the warm climate, while we selected the unpredictable power of wildfire for King’s Landing. We then looked at the energy output of each method to work out how much would be needed. We assumed that those castles needing power stations only needed one. But for castles that require pyromancers…well, we’ll leave that magic to the pyromancers.

Bicycle power: 100W output of bicycle power x 24 hours x 365 days = 876,000. Total kWh/876,000= 1327 x 2 (12 hour shifts).

Solar power: Total kWh/400 kwh p/sqm= square metres/average size of solar panel (1.67275).

Wind turbines: 1 wind turbine creates 6 million kWh of energy per year.

8. Calculating the energy output (and input required) of a dragon. Obviously a dragon is a mythical creature, so we had to be a bit creative here. In the end, we compared the dragon’s fire breathing energy output to that of a flamethrower. To get to that figure, we divided each castle’s total by the energy created, to work out the number of dragons needed.

Flamethrower uses 1/2 a gallon p/second

Gas produces 10,1000 kJ p/gallon

Flamethrower produces 5,055 kJ p/ second

159,414,480,000 kJ in a year

44,281,800 kWh in a year

To work out how much energy Drogon needs to take on board every day, our friends over at Nerdist helped with their fantastic blog post. Once we had the calories needed for a dragon per day, and the calorie count of a human, we could work out how many people a dragon would need to ingest to live for a year, and consequently, how many would be needed to sustain heating at the Great Pyramid.

9. Calculating the CO2 output of Westeros. To calculate the CO2 output of both the firewood and air-conditioning, we looked at the CO2 output in kg per kWh for both totals here, assigning air conditioning units a ‘fuel oil’ fuel source.

What do you think of our calculations? Excited about the new series of Game of Thrones? Let us know on Twitter @OVOEnergy