Do the Energy Bill Analysis

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Our Home Performance services include skills in Building Science, traditional HVAC devices, Safety, Home Comfort and a basic skill in energy and comfort economics. Regarding the economics part of this, as I mentioned in my previous article, Home Performance professionals are expected to make some quick decisions regarding energy saving and comfort impacts for homeowners.

Why economics? …because you deal with a product that has thousands of options. Presenting every combination of choices is confusing for your customer. They want your advice on which option will maximize their comfort and savings for a reasonable investment. They know and you know that it is not cost effective or realistic to consider or invest in every possible measure. So quickly, you’re the expert, which measures deliver the most impact considering the cost?

Answering this question with accuracy is difficult. Even the experts with sophisticated modeling can get it wrong. The best software capable of dissecting every aspect of a customer’s energy consumption after hours of data gathering and input, does not know the return air duct in the attic has come undone. So yes the bills are high, but an air conditioner tune up may not result in significant savings or changes in comfort compared to repairing ductwork.

I actually like some of the software that takes into account hundreds of variables and allows you to play “what-if” with energy efficiency measures. These are great teaching tools that will help you learn about all the potential variables. But I do not think they are accurate enough considering the time it takes to feed the program. In my previous career I reviewed many programs that required volumes of input and simply regurgitated the same, average, somewhat embellished report to guide consumers to energy savings. I now use much simpler methods.

Let’s look at a couple of things you can do quickly to help your credibility and allow you to talk about energy saving impacts. You will not be guaranteeing a dollar savings, but you will sound much more intelligent than others whose reflex answer is, “Well, that’s hard to say”, which really means, “I have no clue.”

The most important thing you need before making any suggested savings is to estimate a home’s current energy usage for heating and cooling. Here is a quick method which takes into account three main portions of an energy bill; heating, cooling and base appliance usage. We will start with the most difficult type of energy history and that is the home that is total electric.

You will need to see at least one year of energy bills. List the 12 monthly bills and note that a typical home in a heating and cooling climate will have lower consumption for a month in the fall and also in the spring. The low bill, or an average of both low bills, is a good estimate of how much this family uses for all non-heating and non-cooling appliances. I call it the base appliance usage. Now I make a very rough assumption that this base usage is about the same in all 12 months. Then I subtract the base usage from every winter month and the remainders are an estimated winter weather related usage. Subtract the base appliance use from the summer months to estimate the summer weather related energy use.

Here is an example of a total electric home’s energy use and my quick analysis:

Click to enlarge.

This can be a relatively quick exercise and surprisingly enlightening for a homeowner to see where their energy is going and where to focus their efforts. In this example, the total annual energy use is high, but it does not appear to be the new heat pump I installed for them two years ago. The heating is a bit high, but we had a cold winter, so from my experience, the heating portion looks appropriate at about $900. (In a normal winter I would expect more like $700 to $800.) This bill analysis and my experience help me make some quick economic decisions.

Why does this family have a high energy bill? For a family of 3, the base appliance usage is relatively high. You may not recognize this until you have researched energy use from hundreds of homes, but you should at least know now that insulation or HVAC improvements will not likely affect this base appliance usage. It’s possible that greater impacts could be achieved with hot water measures, lighting, dehumidifier changes, or daily energy use practices. Unfortunately telling the customer to take shorter showers and use cold water in the laundry may cut into our home performance profits, but it will also keep you much more credible before you promise huge savings on the heating and AC bills that are not really too bad.

A bill analysis is even easier with gas heated homes. Use the electric bills to determine the estimated base appliance use and the air conditioning. Then list the gas bills to estimate the cost to heat. Remember to consider the base gas appliance costs. For example, if you see the four summer gas bills to be in the mid $20s, assume this amount is the amount used for gas water heating and subtract this from the winter bills. (Gas water heating could be a bit more in the winter compared to summer so you could add a bit to this base gas cost for the winter months.)

Why take the time to do this? Because when you analyze more and more energy consumption histories, you will soon have a better sense of how to achieve the greatest impact. High base usage? See the example above. High heating only? I wonder if the crawl space is insulated. High summer use only? I better ask more questions about the swimming pool pump before I quote huge savings from added insulation. High heating and cooling? Now I can start looking at insulating the ducts in the attic or other needed shell measures.

Remember, looking at a customer’s bills is a revealing look at more than the home and the HVAC system. It also includes lifestyle! There are few programs that can do this without 152 input questions. Impress your customers with a bill analysis and follow up with some appropriate measures to maximize the impact.

This article is part of a series of articles by Dan Welklin. Read the first article in the series, “Five Home Performance Skills: Do You Skip Any of These?”

Dan Welklin
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Posted In: ACCA Now, Building Performance, Residential Buildings

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