My neighbor, who lives on the top floor, recently added another floor to his apartment. Since all the solar heaters sat on the roof, he needed to move them. First he moved them to a neighboring roof, and after his expansion was complete he moved them back onto the new roof. In the course of all this movement he destroyed the solar panels of my ten-year-old solar heater. How much does he have to pay for the damages?
There are a number of issues that need consideration. The first is that the solar heater is part of your apartment. Normally (See Mishna Bava Kama 55B), the amount that must be paid is the difference in value between what the object was worth before the damages and what it is worth after the damages. One could therefore, argue that you deserve nothing because the value of your apartment did not change as a result of the damage. If you wish to sell your apartment you will get the same amount if you have a ten year old solar boiler or none at all.
We discussed this issue previously in discussing one who broke a window (Nov 2018) and wrote that today the consensus is like the Chazon Ish that for something that will be replaced, one looks at the item that was damaged as a separate entity and not as a part of the entire house.
Therefore, we have to look at the solar heater as a separate entity. Your neighbor is liable for the damages he caused.
You mentioned that the solar heater was already ten years old. Obviously, ten year old solar panels are not worth the same as brand new ones. Moreover, since practically no one buys ten year old solar panels there is no market price for them. Therefore, in calculating the value of the damages we are in a very difficult position. If there was a market for ten year old panels then our task would be easy. We would just fix the value of the damage as the cost of ten year old panels. However, since there is no market, we must determine another way to evaluate the damages.
This question is not widely discussed among the earlier poskim. Contemporary poskim have suggested different approaches. Apparently in earlier generations there was a market for used goods, whereas today, besides cars and houses, there is almost no market for used goods.
One approach was suggested by Rav Dov Landau (Zecher Tov 8, 17). He bases himself on a Meiri (Bava Kama 40B) and rules that one must pay the amount the owner of the panels would have been willing to spend in order to prevent the damage from taking place. The logic is obvious: the amount the owner would be willing to pay in order to prevent the damage is the amount that the object is worth to its owner. The drawback of this method is that it is very difficult to apply. One person will pay more and another less, making it very difficult to determine a price.
A second approach was suggested by Rav Nissim Karelitz (recorded in Shimru Mishpot 1, 110). He suggests taking the price of a new object and dividing it by the average lifespan of the object. For example if solar panels usually last fifteen years and new solar panels cost fifteen hundred shekels, he would say that in your case your neighbor must pay five hundred shekels because there were five years left for your solar panels.
The Mishpot Hamazik (1, 32, footnote 13) questions that this is not uniform since some people will use an object more than others. However, one can answer that we take an average since there is no way to get an exact amount. We find that Chazal acted this way. For example, there is a measure of the size of an olive, egg etc. Not all olives or eggs are of the same size, yet Chazal gave a measure.
A second objection of the Mishpat Hamazik is that the level of performance usually declines as time passes. Therefore, he feels it isn’t proper to value each year equally. However, one can argue that this is factored in since the value has also declined.
A third approach was suggested by Rav Shlomo Zalman Auerbach and is followed by many today including Rav Naftoli Nussbaum. This method is to figure how much the owner of the used object would be willing to pay to exchange his used object for a new object of the same kind, and then to deduct that amount from the cost of a new object. For example, if you are willing to pay seven hundred shekels to exchange your old solar heater for a new one, then the damage would be eight hundred shekels since one subtracts seven hundred shekels from the fifteen hundred shekels which is the price of new solar panels.
It is very important to note that we only consider intrinsic value. For example, if one owner would not give anything to exchange his old object because it has sentimental value for him we ignore the sentimental value since it is not part of the intrinsic value of the object.
There is another issue: there is a cost to transport and install the new panels. Does the one who damaged have to pay for this as well since this is an expense that resulted from the damage?
The opinion of the Mishpat Hamazik (ibid footnote 9) is that your neighbor who damaged you has to pay the cost of installation as well, since everyone who purchases solar panels has this expense and your neighbor damaged installed panels. Therefore, one must add the cost of installation to the cost of the panels.
Concerning delivery costs he is uncertain because these are not uniform as they depend on the locations of the customer and the supplier. Therefore, it is difficult to include these in the value of the solar panels. However, even if beis din may not be able to force the neighbor to pay this part of the damage, it seems proper for him to pay anyway since they are certainly causative damages for which one is liable in the heavenly court of justice.
We should note that your neighbor does not need to pay full installation and transportation costs since there is depreciation here as well. Thus if solar panels normally last fifteen years and yours were ten years old, he will need to pay just one third of these costs because you already derived two thirds of the value of these costs.
In conclusion: Your neighbor must pay you for the damages he caused. The amount must be assessed according to one of the methods described above for calculating the damages. He must also pay an appropriate portion of installation costs and perhaps delivery costs. One must take into account the age of the panels as described above. It is proper to consult with a knowledgeable rav or a beis din to determine the amounts.