If the cold snap has you turning on your heater more often, you might be wondering what awaits you in your next power bill.

New Zealand hit record levels of power consumption on Wednesday as temperatures dropped

If the cold snap has you turning on your heater more often, you might be wondering what awaits you in your next power bill.

New Zealand hit record levels of power consumption on Wednesday as temperatures dropped across the country, and the same is expected on Thursday.

But what does that mean for what households are paying?

Energy Efficiency and Conservation Authority lead adviser Gareth Gretton said normal heating would add about $150 a month to a power bill when a household relied on electric heaters.

He calculated that using the example of Christchurch, because it does not have natural gas. “There’s roughly a $150 difference between August, which is the coldest month, and February, which tends to be one of the warmest. So that’s roughly $150 for heating in August.”

He said a cold snap, with temperatures at least 5C lower than normal, would add another 50% to heating bills.

“Bearing in mind that it’s cold in August anyway, that’s kind of what a cold snap looks like.

“As a really rough guide you’d maybe be talking $15 or $20 extra heating costs a week for the unseasonably cold or particularly cold winter weather.”

He said people who were worried about the cost of heating could focus on only heating the rooms they were in.

“All being in the main living room and using the heat pump, which is probably in the main living room and is the most efficient form of heating as well.

“A common set-up is you’ve got a heat pump in your main living room but you’ve maybe got just electric panel heaters or something in the bedrooms … we’re certainly still encouraging people to heat bedrooms when they’re in them but if you really are trying to shave your costs then just heating the rooms that you’re actually in at the time you’re in them is kind of the best way to go.”

Powerswitch general manager Paul Fuge said people needed to remember electricity bills were not driven solely by how much power a household used.

“While colder weather typically increases electricity consumption, the relationship between usage and bills isn’t one-to-one. Around 35% to 40% of a typical household power bill is made up of fixed or largely fixed charges, such as transmission, local lines and metering costs. These costs remain the same regardless of how much electricity a household consumes.

“The impact can be larger or smaller depending on the household’s pricing plan and how much electricity they use during peak demand periods.”

He said other things were also a factor. Houses with solar panels would often have less electricity generation in winter because the days were shorter.

“For households on time-of-use plans, winter can also make it harder to shift some electricity use for space heating away from peak periods. Heating demand is often concentrated in the morning and evening when people need it most, and these are typically the times when electricity is most expensive. As a result, households can end up consuming more power during peak pricing periods than they typically would, which can magnify the impact on their bills.”

He said households that had people home for much of the day, such as those where people worked from home or were looking after young children, would often receive bigger winter bill increases because they had to heat all day long.

“It’s also worth noting that there’s usually a lag between cold weather and the bill arriving. Most households are on post-pay plans, so higher usage during August won’t typically show up until the September bill, by which time the weather may have already improved. In general, it’s not uncommon for a household’s power costs in the coldest months to be around 60% higher than in the warmest summer month.”

Fuge said while recent demand had pushed wholesale electricity prices up at times, most households were insulated from short-term fluctuations.

“Retailers typically manage this risk through hedging arrangements and long-term electricity purchases, allowing them to offer consumers fixed or predictable pricing. While sustained high wholesale prices eventually flow through to retail prices, the recent wholesale spikes were brief, so I wouldn’t expect them to have a material impact on longer-term retail electricity price trends.”