Every energizer gets a score from 0 to 100% built from four factors, which maps onto the 5-point rating shown on the site (a 0% score would be 1.5 stars; a perfect score, 5). Each factor is scored against fixed reference points, not against the other products in the list, so adding a new model never moves another model’s rating. Energizers are grouped by power source, plug-in and battery or solar.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per joule of output energy | 35% |
| Output | output energy delivered to the fence | 25% |
| Warranty | warranty length | 25% |
| Lightning cover | warranty covers lightning damage | 15% |
Where the numbers come from
Output and stored joules, rated fence length, voltage and warranty terms come from the maker’s spec sheet, manual or product page. Prices are checked at Amazon, the maker’s own store and farm retailers, and the lowest is used.
The factors
Value is the current price divided by the output joules, on a log scale, so halving the price per joule always counts the same. Plug-in energizers score zero at $500 per joule and full marks at $15; battery and solar energizers, which carry a battery or panel, score zero at $3,000 and full marks at $40.
Output is the output energy per pulse, on a log scale. Plug-in energizers score zero at 0.2 J and full marks at 15 J; battery and solar energizers zero at 0.05 J and full marks at 4 J. When a maker publishes only stored joules, output is taken as 70% of stored, a typical ratio among makers that publish both, and the factor is marked estimated.
Warranty is the maker’s warranty: 1 year scores zero and 3 years full marks.
Lightning cover is full marks when the warranty explicitly covers lightning damage, and zero when it doesn’t.
What isn’t scored
Stored joules (except as a stand-in for output), rated miles and acres, peak voltage, low impedance design, battery voltage and solar panel size are listed but not scored. Rated miles assume ideal conditions and aren’t comparable between makers.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated. The exception is warranty: a maker that doesn’t publish one gets no warranty counted, so that factor scores zero, the same as the shortest warranty on the scale, and is marked estimated.
Ties and discontinued models
Products are ranked by score within each group. Discontinued models stay listed but rank below every current model and can be hidden with the “Hide discontinued” filter.