A geyser blanket is one of the cheapest energy-saving buys in a South African hardware store, and every winter the same question comes up: does it actually save money? The short answer is that it depends on how old your geyser is. On an older geyser with bare pipes, a blanket and some pipe lagging save a modest but real amount. On a geyser made since 2016, the blanket adds little, and lagging the pipes is the better use of your money.
This guide explains what a blanket does, how much heat a modern geyser already holds in compared with an older one, and what the South African evidence says about savings. It includes a worked example with every assumption stated, a plain verdict, and the parts of the geyser you must never cover.
Key takeaways
A blanket reduces standing losses, the heat a hot tank leaks all day. It does nothing to the energy needed to heat the water you use.
Since 2016, a 150-litre geyser may lose no more than 1.40kWh a day, against 2.59kWh under the old rule. Blankets help older geysers most.
South African research cited by the LBNL study found a blanket saved up to 0.2kWh a day on old geysers, while lagging the first 3m of the hot outlet pipe saved about 0.3kWh a day.
Lag the pipes first, then add a blanket if the geyser predates 2016, sits outside or in a cold roof space, or feels warm to the touch.
Never cover the thermostat and element cover, the pressure or temperature relief valve, the drain valve or the rating plate.
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What a geyser blanket does
An electric geyser loses energy in two ways. Most of it goes into heating the water you use: each litre drawn is replaced with cold water that the element must heat. The rest is standing loss: heat escaping through the tank's insulation, its fittings and the pipes attached to it, 24 hours a day, whether anyone opens a tap or not. When the water cools a little, the thermostat switches the element back on to replace that heat.
A blanket is an extra layer of insulation wrapped around the outside of the tank. It slows the standing loss through the casing. It can't touch the energy used to heat your shower water, and it does nothing for heat escaping through the pipes and valves. That's why the pipes matter as much as the tank.
How much heat does your geyser already keep in?
All electric geysers sold in South Africa must meet SANS 151, which caps how much heat a tank may lose in 24 hours. In 2016 the cap was tightened by compulsory specification VC 9006. According to the 2024 South African water heating study by Lawrence Berkeley National Laboratory (LBNL) and the University of the Witwatersrand, a 150-litre geyser may now lose no more than 1.40kWh a day, down from 2.59kWh.
150L geyser made since 20161.40 kWh
150L geyser under the earlier limit2.59 kWh
Maximum standing loss in 24 hours under SANS 151 (LBNL and Wits, 2024)
So a newer geyser may lose only a little over half as much heat as an older one, and a blanket has much less to improve on. The LBNL study says this directly: standing-loss standards have been strengthened, and adding blankets to the more efficient geysers will have a diminished impact.
Older geysers are still common. The study estimated that 44.8% of South Africa's geysers in 2023 still had the older insulation rating, falling to 13.8% by 2033 as tanks are replaced. To check yours, look at the rating plate on the side of the tank for the manufacture date. Eskom's hot water factsheet makes the same distinction: new geysers are well insulated, and an older geyser may benefit from an insulation blanket.
The pipes leak more than you might think
The SANS 151 test measures the tank on its own. In a real house, heat also escapes through the hot outlet pipe, the valves and the fittings. The LBNL study compared measured standby losses in South African homes with the laboratory limit for older 150-litre geysers. The field figure was 172W against the 127W allowed for the tank, a difference of about 45W, or roughly 1.1kWh a day lost through pipes and fittings. The study recorded this on older geysers, so a newer geyser's pipe losses may differ.
That is why plumbing standards already expect pipe insulation. The LBNL study notes that SANS 10252-1 requires insulation on hot water pipes, valves and couplings, and on cold water pipes within 1m of the geyser. It also says that requirement isn't consistently applied, especially in older buildings, and that pipe insulation wears over time, particularly outdoors. For new buildings, the NHBRC's energy efficiency guidelines state that under SANS 10400-XA all hot water service pipes must be clad with insulation, with a minimum R-value of 1.0 for pipes up to 80mm in diameter.
What the evidence says about savings
There is less hard South African data on blankets than the number of tips online suggests. The most specific figures come from 2009 research by the Cape Peninsula University of Technology, as cited in the 2024 LBNL study:
A correctly installed geyser blanket reduced standing losses by up to 0.2kWh a day. That figure is for old, lower-rated geysers.
Insulating the first 3m of the hot water outlet pipe saved about 0.3kWh a day.
In other words, on an older geyser the pipe lagging saved more than the blanket. Eskom's factsheet advises insulating the geyser and the water pipes "for the maximum benefit". The City of Cape Town's "Top ways to save" leaflet recommends both a blanket and hot pipe insulation, though it doesn't give a figure for either.
No current South African source gives a measured saving for a blanket on a geyser made since 2016, so we don't give one either. Based on the LBNL finding, expect less than the 0.2kWh a day measured on old geysers.
Worked example: an older geyser in the ceiling
Assumptions:
A 150-litre geyser made before 2016, in the ceiling, with bare pipes.
Savings at the top of the measured range: 0.2kWh a day from the blanket and 0.3kWh a day from lagging the first 3m of the hot outlet pipe.
Electricity at R3.56 per kWh, the 2026/27 Eskom Homepower rate including VAT (energy, network demand and ancillary charges, before the fixed daily charges). Municipal rates differ, so check yours on our electricity tariff tracker.
A 30.4-day month.
Measure
Energy saved
Saving per month
Saving per year
Geyser blanket
up to 6.1kWh a month
up to about R22
up to about R260
Lagging the first 3m of hot pipe
about 9.1kWh a month
about R32
about R390
Both
about 15.2kWh a month
about R54
about R650
The LBNL study put the cost of a geyser blanket at under R500 in 2024, and installation at under an hour. On this older geyser, a R500 blanket would take about two years to pay for itself at the best measured saving. A cheaper blanket pays back faster, and so does a geyser in a colder spot. On a geyser made since 2016, the payback is longer. Pipe lagging is usually the faster payback, but check current prices at your local hardware store, because we haven't verified them.
These are SolarGuide calculations from the published figures, not measured results for your home. Our geyser cost calculator shows what your whole geyser costs to run, which puts these savings in context.
The honest verdict: when is a geyser blanket worth it?
Lag the pipes first, almost always. It is the measure with the bigger measured saving, plumbing standards already expect it, and it helps old and new geysers alike. Cover at least the first 1m to 3m of the hot outlet pipe and the first metre of the cold inlet, including elbows and valves where you can do so safely.
Add a blanket if any of these apply:
The geyser was made before 2016.
It is outside, or in a draughty or uninsulated roof space where the surrounding air gets cold.
The outer casing feels warm when you touch it. That warmth is heat escaping.
You've already lagged the pipes and fitted a timer, and want the next small saving.
Skip the blanket, or treat it as optional, if:
The geyser is less than about ten years old, indoors and cool to the touch.
The manufacturer's instructions say not to add external insulation.
The geyser is due for replacement soon. Put the money towards a better water heater instead. Our guide to the types of geyser compares solar, heat pump and hybrid options.
A blanket and lagging only trim the smaller part of the geyser's energy use. For a bigger cut, look at the thermostat and the schedule. Our guide to geyser timer settings shows how much a timer, a 60°C thermostat and time-of-use or solar heating can save.
How to fit a geyser blanket safely
Get help if the geyser is hard to reach, or if you aren't comfortable working in the ceiling. Then follow these steps:
Switch off the geyser at its isolator or the distribution board before you start.
Check the geyser and its instructions. If you see rust, damp, drips or a full drip tray, call a plumber instead. A blanket can hide a leak until it becomes a burst. The US Department of Energy's installer guide also says to confirm the manufacturer doesn't prohibit extra insulation.
Mark the cut-outs before wrapping, so nothing important ends up underneath the blanket.
Wrap the tank with the seam where you can reach it, then tape it and secure it with straps. Don't pull the straps so tight that they squash the insulation, because compressed insulation works less well.
Lag the pipes with sleeves sized to each pipe and rated for hot water, and seal the joints.
Switch the geyser back on and check that nothing is touching the electrical cover.
Never cover these:
The thermostat and element cover, where the electrical connections are. It must stay accessible and must not be enclosed in insulation.
The pressure control valve and the temperature and pressure relief valve, and their discharge pipes.
The drain valve, the vacuum breakers and the drip tray.
The rating plate, which you or a plumber may need later.
The Department of Energy guide gives the same core rule: added insulation must not obstruct the relief valve, the thermostats and controls, or the access plates. If adjusting the thermostat or opening the element cover is part of the job, switch off the power and leave it to an electrician or plumber.
Geyser in the ceiling versus outside
How fast a tank loses heat depends on the gap between the water temperature and the air around it. A geyser indoors or in a ceiling sits in warmer, still air. A geyser mounted outside faces cold nights, wind and rain, so it loses heat faster, and the LBNL study notes that insulation exposed to the elements wears more quickly.
That makes an outdoor geyser the strongest case for extra insulation, but only with products made for outdoor use. An indoor blanket isn't designed for rain or sun, so check that the product is rated for outdoor use. For outdoor pipes, choose lagging that resists sunlight, or cover it. If your outdoor geyser is old, replacing it may make more sense than wrapping it.
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Frequently asked questions
Do geyser blankets work on new geysers?
They work, but they save much less. Since 2016, South African geysers have had to meet a stricter heat-loss limit, and the 2024 LBNL study says blankets have a diminished impact on these more efficient tanks. Lagging the pipes is usually the better buy for a newer geyser.
How much does a geyser blanket save?
South African research cited in the LBNL study found up to 0.2kWh a day on old geysers. At R3.56 per kWh, that is up to about R22 a month. Lagging the first 3m of the hot outlet pipe saved about 0.3kWh a day, or about R32 a month at the same rate.
Should I insulate the cold water pipe as well?
Yes, the first metre. Heat travels back along the cold inlet pipe near the tank, and the plumbing standard SANS 10252-1, as described in the LBNL study, includes cold water pipes within 1m of the geyser in its insulation requirement.
Is it safe to fit a geyser blanket myself?
It is a simple job if the geyser is easy to reach. Switch the geyser off first, and never cover the thermostat and element cover, the valves, the drain or the rating plate. If you see signs of a leak, call a plumber instead.
Is SolarGuide the installer?
No. SolarGuide is an independent referral partner. Alumo supplies, installs, finances and warrants the solar systems we refer. We help you compare options and get a free quote. All pricing is indicative and subject to a site assessment and credit approval. We don't sell or fit geyser blankets.
SolarGuide is an independent referral partner. We help you compare options and arrange a free quote — Alumo supplies, installs, finances and warrants the systems. Pricing is indicative, sourced from Alumo’s published catalogue, and subject to a site assessment and credit approval.
