House rules

House rules determine how a sportsbook settles your bet. Two books can post the same line on the same game and still settle differently.

Why +EV bettors care

EV calculations don't account for house rules. It's important that the user understands this before placing a bet. Below we will discuss common examples across several sports.

MLB

Batter Props house rules are the most important to understand when analyzing EV results. Most notably, certain books require the batter to start the game for the bet to stand, and other books only require a plate appearance.

Example

Below we see a few EV plays on Hard Rock that are devigged against NoVig. They look great at first glance.

However, Hard Rock requires the batter to start for action, and NoVig only requires a plate appearance. If a batter pinch hits late into the game and only gets 1 plate appearance, they typically have a much lower chance of recording a Run or RBI. NoVig odds may be accounting for this scenario. The EV calculations do not. The Under on Hard Rock could be a false +EV signal.

To alleviate this issue, wait until starting lineups are posted. At that point EV calculations are typically reliable.

Conversely, you may be able to take advantage of the inverse scenario. Below is an example.

If starting lineups haven't posted yet and there's a chance that Kyle Manzardo doesn't start, then the Over on Hard Rock is even better than the scanner shows. ProphetX has the same action rules as NoVig here.

More

There are other house rule differences, such as starting pitcher changes. For more information, read https://about.darkhorseodds.com/guides/house-rules-comparison. When in doubt, double check the house rules before trusting EV calculations.