Intro to Rules Engine

Glossary

• billing period: For a given bill that a homeowner is charged for their heating usage, the billing period is the time range (defined by a start date and an end date) for which they are being billed. On the HEAT app, users will upload their heating usage data for multiple billing periods.
• BTU: British Thermal Units - a common measuring unit for heat
• UA: also known as the heat transfer coefficient, UA is a measurement of how quickly a home loses heat
• Balance point: the outside temperature above which no heating is required for a given home to maintain its desired interior temperature. By definition, the balance point is less than or equal to the thermostat set point.
• Thermostat set point: the average interior temperature that is desired by the homeowner, that they program their thermostat to
• Heating Degree-Days (HDD): For a single day, HDD refers to the number of degrees between the outside temperature and the balance point (when the outside temperature is colder than the balance point - if outside temp is >= balance point, no heating is required and HDD = 0). More HDD = more energy required to heat the home. For a multi-day time period, the total HDD is the sum of the single-day HDDs. every day where the outside temperature is below the balance point temperature requires active heating. HDD refers to the sum of these temperature differences within the time period.
• Average heat load: the amount of energy that a home needs to be added from a heating system in order to maintain a desired temperature on an average day
• Max heat load: the amount of energy that a home needs to be added from a heating system in order to maintain a desired temperature on a really cold day (the design temperature)

Rules Engine Steps

1. Read in the billing periods data and categorize them by season.
2. Calculate the average daily non-heating usage (if fuel type is gas, this is the average daily summer-month usage. Otherwise, it's 0)
3. Calculate the average daily heating usage (average daily total usage in winter months minus average daily non-heating usage)
4. Calculate the UA and the balance point. This is a semi-iterative process
5. Calculate average indoor temp: ((24 - setback hrs per day) * tstat setting + setback hrs per day * setback temp)/24
6. Calculate avg heat load: (design set point - (avg indoor temp - balance point) - design temp) * UA
7. Calculate max heat load: (design set point - design temp) * UA