Water Heating, Cooking & the Rest

Water heating is one of the largest energy uses in a home after space conditioning, so how it is electrified matters. There are three electric routes, and they differ enormously in efficiency. The crudest is the resistance geyser - the familiar electric water heater with an element inside. It is cheap and simple, but like any resistance heater its efficiency is about one: one unit of electricity becomes one unit of heat, no leverage. It works, but it is the least efficient way to make hot water with electricity.

The efficient electric route is the heat-pump water heater, which applies the previous lesson's magic to water: instead of making heat with an element, it uses a small heat pump to move heat (typically from the surrounding air) into the water tank, so it delivers several units of heat per unit of electricity - a COP well above one, often in the range of two to four. For the same hot water it uses a fraction of the electricity of a resistance geyser. The trade-offs are a higher upfront cost, a larger unit, and a preference for warm surrounding air (which suits much of India well and which is why it pairs naturally with the country's climate).

The third route barely uses electricity at all: solar water heating, where a rooftop solar thermal collector heats water directly with the sun, backed up by an electric element for cloudy days and peak demand. In a sunny country this is superb - much of the year's hot water comes free from the sun, and India has deployed solar water heating widely for exactly this reason, in homes, hostels and hotels. It is often the single most cost-effective electrification move for hot water in the Indian climate. The honest caveats are the upfront cost, the roof space and plumbing, and the need for a backup, but the running economics are excellent. Across all three, the binding decisions - tank sizing, storage volume, recovery rate, and the legionella-safe temperatures and safety controls that hot-water systems require - are a plumbing and mechanical engineer's, not a rule of thumb; the designer's job is to choose the efficient strategy (favour solar and heat-pump over resistance where feasible) and leave the sizing to the specialist.

Cooking uses relatively little energy compared with comfort or hot water, but it carries outsized weight in habit, culture and - as the next section argues - health. The electric way forward is induction cooking, and it is worth understanding why it is different from the old electric coil. An induction hob does not heat itself and then heat the pot; it uses an electromagnetic field to induce heat directly in the base of the pan. That means very little energy is wasted heating the air or the cooktop - a large share of the energy goes straight into the food, making induction the most efficient way to cook, more efficient than both the resistance coil and the gas flame (which loses much of its heat to the air around the pot).

Beyond efficiency, induction is genuinely good to cook on. It is fast - water boils quickly because the power goes straight into the pan - and it is precise and responsive, changing power instantly like a gas flame and more controllably than an old coil, which addresses the classic cook's objection that electric cooking is sluggish. The surface stays cooler and is easy to clean, and there is no open flame, which is safer around children. The practical requirements are modest but real: induction needs induction-ready cookware (magnetic-base pans - most steel and iron work, aluminium and some others do not), and it needs adequate electrical circuit capacity, since a hob can be a significant load - a point to confirm with an electrician rather than assume.

In the Indian context, induction has spread fast for good reasons - portability, no cylinder to refill, precise control - but it meets real friction too. Many traditional cooking techniques and utensils assume a flame; some cooks strongly prefer the visible flame for charring, roasting rotis directly, or the feel of the craft; and, crucially, induction stops when the power fails, which in areas of unreliable supply is a serious drawback that keeps an LPG backup in many kitchens. Honesty matters here: induction is the efficient, healthy, controllable choice and the direction of travel, but in India it often coexists with LPG rather than instantly replacing it, and a good design respects that transition rather than pretending it is finished. The circuit capacity and any dedicated wiring are the electrician's to confirm.

With comfort, hot water and cooking electrified, what remains? Less than people expect, because most of a modern building's other loads are already electric. Lighting, fans, refrigeration, electronics, pumps, lifts and machines all run on electricity today and simply continue - the electrification job there is not conversion but efficiency (LEDs, efficient motors and appliances, good controls), which belongs to the efficiency-first discipline of Module 1.4. A few specific loads are worth naming because they are sometimes still fossil-fired or newly significant.

Clothes drying, where present, can move from a gas dryer to a heat-pump clothes dryer, which - true to the pattern of this module - moves heat rather than making it and so uses far less energy than a resistance dryer; in much of India, of course, the sun still does this job for free. Space and water heating in larger or commercial buildings may use fossil-fired boilers or process heat that can be electrified with larger heat pumps or, for high-temperature process needs, other electric technologies - a specialist area, but the principle is the same. Pools and spas, common in hospitality, are strong candidates for heat-pump heating. And the big new electric load that this course treats separately is electric-vehicle charging (Module 3.4), which is not a replacement for an old flame but a genuinely new demand that all-electric buildings increasingly must plan for.

The unifying point is that once the flames are gone - heating and cooling, hot water, cooking, drying, backup - the building's entire energy demand is electric, and the remaining agenda is to make every one of those loads as efficient as possible and, later, as flexible as possible. That is the shape of the all-electric building: a manageable set of electric loads, most of them already electric, a few converted from combustion, all of them then candidates for efficiency and, in the grid-interactive future, for shifting in time. As always, the actual loads, circuit sizing and total electrical capacity these add up to are an electrical engineer's calculation governed by the codes - the designer's job is to know the loads exist, favour the efficient options, and plan for capacity early.

Now the argument this lesson has been building toward, and the one that often persuades people who shrug at carbon: indoor air. When a flame burns inside a home - a gas or LPG hob, a gas water heater - it is a combustion source in the room where people cook, eat, and breathe, and combustion produces pollutants. A gas or LPG cooking flame emits nitrogen dioxide, carbon monoxide and fine particulate matter into the indoor air, often close to the person cooking and frequently in a kitchen with limited ventilation. These are not exotic risks; they are ordinary combustion products, and reducing them is a straightforward public-health good. Electrifying cooking and water heating removes that indoor combustion source entirely - no flame, no combustion products in the room. Induction and electric water heating are, in this sense, a wellbeing upgrade as much as an energy one.

This argument lands with particular force in India and the wider developing world, where the health stakes are highest. Hundreds of millions of households still cook with solid biomass - firewood, dung, crop residue - on open or poorly vented stoves, and the resulting household air pollution is one of the largest environmental health burdens there is, falling hardest on women and children who spend the most time near the hearth. Moving up the ladder from biomass to LPG was itself a huge health gain, and moving further to clean electric cooking removes indoor combustion altogether. Framing electrification as a health intervention - cleaner air in the home - is often more motivating and more equitable than framing it purely as climate action, and the two goals point the same way.

Keep the honesty intact. Getting combustion out of the home is a clear indoor-air win, but it is not a claim about the building's carbon (that still tracks the grid) and it does not erase the transition's frictions - the cost of new appliances, the loss of a flame some cooks prize, and the reliability worry where power is intermittent. Nor does the designer measure or certify air quality - exposure assessment and ventilation design are specialist and code-governed domains. What the designer can do is champion the electric, combustion-free home as a genuine health improvement, design kitchens and homes around it, and set expectations honestly. The healthiest home has no flames in the rooms where people live - and electrification is how you get there.