Upgrading Electrical Installations in Pre-War Apartments

Michael Tobias
6 Minutes Read
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    Pre-war apartments are those built before World War II, as implied by their name, and in New York City they are highly sought after due to their antique look, spacious design and hand-crafted details. However, their electrical installations are often very outdated, and require upgrades to accommodate a modern lifestyle. Keep in mind that pre-war apartments were built more than 70 years ago, when residential energy consumption was much lower:

    • Air conditioning systems became mainstream after World War II, which means the electrical wiring in pre-war apartments was not designed for them.
    • Computers and electronic gadgets are even more recent, dating from the 80s. Although these devices don’t consume a lot of energy, they tend to induce high-frequency currents called harmonics, which overheat wiring.
    • Heating was accomplished mostly through fireplaces, and they are part of the charm of pre-war apartments. However, it also means these apartments are generally not equipped to handle a resistance-based space heater or water boiler.

    In short, the electrical wiring of pre-war apartments was designed for a time when there were few loads other than lighting, radios, TVs and kitchen appliances. You can’t expect to buy or rent one of these apartments and install modern water heaters and air conditioners right away. However, upgrading their electrical system doesn’t have to be a complicated task; you only need proper guidance from an engineering professional or company.

    Electrical Systems in Pre-War Apartments: Recommended Steps

    The basic rule when upgrading the electrical system of a pre-war apartment is the following: if you can minimize the current required, upgrade costs will be lower and you will run into fewer issues in the long run.

    1) Implement Energy Efficiency

    If you use energy-saving devices such as LED bulbs and ENERGY STAR appliances, the load on the installation will not increase drastically compared to the conditions in which you receive the apartment. This can be complemented with home automation; for example, you can use a smart thermostat to optimize HVAC power consumption.

    2) Use 220-Volt Appliances Whenever Possible

    One of the basic principles of electricity is that power transmitted is equal to the product of voltage and current:

    Power = Voltage x Current

    However, wiring and breakers are sized based on current, and a higher capacity involves a higher cost. Increased current capacity also means wiring must have a larger diameter, which complicates its installation and drives up the associated labor cost. However, increasing the operating voltage reduces current, and this can be proved mathematically by rearranging the previous formula:

    Current = Power / Voltage

    If you must choose between 110 V and 220 V versions of the same appliance, using 220 V reduces the current by 50 percent. To illustrate the concept, assume you need a 3.3-kilowatt water heater that is available with both voltages:

    • Current Drawn with 110 V = 3,300W / 110V = 30 Amperes
    • Current Drawn with 220 V = 3,300W / 220V = 15 Amperes

    With the 110-V heater, you require a larger cable and the circuit will emit more heat. This can cause breakers to trip more frequently, and can also damage other electrical components due to how old the installation is.

    3) Upgrade the Installation Accordingly

    With energy-efficient appliances and using 220-V devices whenever possible, the total current is reduced significantly. Now you can ask your electrical contractor to size the new installation accordingly. This reduces the required capacity of electric panels, breakers and circuits, saving money upfront.

    Conventional lighting and HVAC will result in a more expensive renovation and a higher operating cost. In addition, you are more likely to have electrical issues because an old installation will be subject to high current and localized heating.

    Main Challenges During a Power Upgrade for a Pre-War Apartment

    The construction features of pre-war apartments increase the difficulty of electrical upgrades, compared to modern dwellings.

    • Pre-war apartments typically have monolithic floors of poured concrete with a wooden pattern on top, which makes it impractical to embed conduit for new electrical wiring. In newer apartments, on the other hand, a thin concrete layer is mounted on a steel structure, which results in plenty of empty space for electrical installations.
    • Thick walls are another feature of pre-war apartments. They are normally built from layers of plaster and concrete, with an underlying lathe made of wood or wire. Modern walls, on the other hand, typically use thin gypsum boards on wooden or metallic frames; and punching into the wall to install new wiring or electrical components is relatively simple.

    These construction features come from the engineering philosophy of the pre-war era, when labor was cheaper but materials were expensive; it made sense to use rugged and durable materials even if their installation was labor-intensive. Now materials are affordable but the cost of labor has risen considerably, shifting the emphasis from rugged construction to fast installation.

    Due to the sturdiness of walls and floors, in many pre-war apartments there is no choice but to use superficial electrical circuits. However, they can be hidden under specially-designed decorative moldings to preserve the antique appearance.

    Electrical Protection Systems

    Fuse boxes in pre-war apartments are normally from discontinued product lines, and in some cases the brand itself may no longer exist. For this reason, it is often necessary to replace them completely with a new panel and circuit breakers. Direct replacement of the existing fuses is normally not possible because the existing bases don’t match those of modern protection systems.

    Keep in mind that in many buildings there is main distribution board from which all apartments draw power. In these cases, it may also be necessary for the building owner to upgrade to a modern panelboard and breakers.

    Transformers and Main Service Entrances

    When multiple pre-war apartments in the same building are being upgraded, their combined electrical load can become higher than what the main transformer and service entrance are designed for. In these cases, it is necessary for the building owner or co-op board to carry out an upgrade.

    When purchasing a pre-war apartment, get a professional opinion on the transformer and service entrance conditions. Individual tenants can normally carry out upgrades up to their respective electric panel, but any installations located upstream from that point are the responsibility of the building owner. If you have an apartment with deficiencies in this area and the owner is unwilling to carry out a transformer and service entrance upgrade, you will continue to have power issues even after upgrading your individual installation.

    Who Assumes the Cost of Electrical Upgrades?

    Most pre-war buildings in New York are run like cooperatives: you don’t really buy the apartment, but instead buy shares in a corporation that in turn owns the apartment you will occupy. These cooperatives are run by a board that manages the property and allocates common expenses among all shareholders.

    If electrical upgrades are needed, the first question to answer is: Can they be attributed to the needs of a specific apartment, or is there an issue affecting the whole building? This question can be answered with an electrical load survey by a qualified engineering professional or firm.

    Apartment-Specific Electrical Issues

    If electrical installations need to be upgraded because a specific neighbor has an energy-intensive lifestyle, he or she will generally have to bear the cost of the upgrade. In these cases, a dedicated electrical installation is often installed to avoid modifications to the main service entrance, which is generally much more expensive.

    An example of this would be when on shareholder purchases low-efficiency heating and cooling equipment, and uses it for long hours. The electrical current drawn by that apartment is high and continuous, which taxes the entire installation and may cause voltage issues for everyone.

    Electrical Issues Affecting the Entire Building

    Sometimes the overall electrical installation is too old to meet the energy demand of modern lifestyles, and it may be necessary to carry out a building-scale upgrade. In these cases, the co-op board assumes the cost of the job. However, depending on the cooperative’s rules, the cost may be split among all shareholders in proportion to their ownership stake.

    An example of this would be a building where the main transformer has never been upgraded, and is no longer suitable to manage modern loads, even if all shareholders are energy-conscious.


    If you are going to buy or rent a pre-war apartment, don’t overlook the electrical installation. Expecting the existing installation to work with zero issues would be unrealistic, but you shouldn’t have to assume an extremely high upgrade cost either.

    We recommend you get familiarized with any applicable rules when you interview the real estate company or co-op board, and get a brief electrical assessment of the apartment you will buy or rent. Once you have occupied your pre-war apartment, use energy efficient appliances and be smart when managing your power consumption; for example, don’t use two high-power devices at once unless it is necessary.

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