## How do we calculate savings with a Sterling Home?

We track the Energuide value for a typical home that corresponds with the Sterling model. From this we can calculate a percentage difference between the two houses Energuide values. If we approximate that gas is 75% of the GJ consumed, and electricity is 25% then we can create an approximate cost of energy consumption in the typical home. Now we can use the percent difference in the typical home Energuide value vs. Sterling Energuide value to find the cost of the Sterling model. If a house consumes 20% less energy, it should cost 20% less to run. If you’re comparing a Sterling Homes to an older home on the market that hasn’t been renovated, the savings would be even greater than what the calculator is displaying on our website, as we are comparing the energy performance of our homes against against a new home built to code today.

To fully understand how our energy savings calculator works, we are comparing the GJ/Year usage for this model against the GJ/Year usage of a typical new home. Against a typical older home, the savings would be even greater.

For example, if we look at the project above, we see that a typical home consumes 143 GJ per year whereas a Sterling home only consumes 102 GJ per year, a 28.67% difference. Now looking at the table we can see the average cost for both gas and electricity and work out the cost for a typical home as follows:

CT = (G × CG) + (E × CE)

Where CT = total cost for energy in a typical home, G = amount of gas consumed in GJ, CG = cost of gas per GJ, E = amount of electricity consumed in GJ, and CE cost of electricity per GJ. Now we can use the values in the table below to calculate the total cost.

First we must convert kWh into GJ by using 1GJ = 277.77kW h and thus electricity costs $46.11 per GJ. Using the approximation that gas is 75% of the

GJ consumed, and electricity is 25% we can see:

CT = (107.25GJ × $4.09) + (35.75GJ × $46.11)

CT = $438.65 + $1, 648.43

CT = $2, 087.08

Now applying our model that a Sterling model is X% more efficient and thus should cost X% less to run we would get:

CS = CT × (1 − P)

Where CS = total cost for energy in a Sterling home, and P is the percentage difference between the two models. So in the 9399 example we would have

CS = $2087.08 × (1 − 0.2867)

CS = $1, 488.71

So we can see that by just estimating the typical homes energy consumption, we can scale the savings in a Sterling home based on the difference in consumption. By using CT −CS we can see that a Sterling home would save **$598.37 per year.**

Note: Energuide labels are not included in our specification when purchasing a new home.