Electricity bills

[brianwaring]

Can anyone tell me if yhere is a correlation between lower voltage and higher electric consumption

[rekstout]

Electricity is metered in Kilowatt Hours - that is the equivalent of operating a 1KW appliance for 1 hour. Lowering the voltage would reduce the power output thereby reducing consumption. This does not however take into account the less than perfect efficiency of the transformer dropping the voltage from 240V AC mains supply to - for example - a 12V halogen lighting ring.

[JiverSteve]

I must question the validity of the answer given. If the voltage applied to a device drops, according to ohms law V=I*R then assuming the resistance does not change the current must increace. Since the wattage is calculated as W=I*I*R the wattage remains the same.

[mac309]

I have to agree with Jiversteve with his answer, due to Ohm's Law states that when the resistance(R) remains constant, the voltage(V) is inversly proportional to current(I) therefore if the voltage dropped by 10 percent then the current would increase by 10 percent. This then means that what ever happens, the power(W) will remain the same.

[TheHitMaker]

steve and mac - what are you on about? V=I*R - therefore if V drops and R remains constant, the current must drop as well - take an example I=2, R=2 therefore V=4. If you halve V which becomes 2, then I = 2/2 = 1. Therefore if you halve the voltage, you halve the current. Think about it - if when voltage dropped, current increased then with zero volts you would get an infinite current and alternatively with a current of zero there would be an infinite voltage - which obviously does not happen.

[JiverSteve]

The Hitmaker has missed and needs to go back to school and redo his physics class. If he is right then when the uk supply voltage was dropped from 240 to 230 V then all the electricity companies would have gone bust as they charge by the Kwhr and would have lost 4% if their income. Not only that if we all fitted big transformers to our homes and dropped the voltage then we would all save money. Funny how there are not many on the market.

[Hamish]

Hi folks, rekstout is literally correct. Less power will be used per unit time, however as less power is used, there will be less power output, ie dimmer lights, loger to roast that turkey etc etc. In order to get everything working right you would have to increase the resistance in everything, wich as the rest of the answers show, results in the same power consumption. As to the question over going from 240 to 230, remember this is the rsm of the voltage (did the bredth of distribituion change). This aside, the possible savings on transformer efficency etc mak make up for the seeming loss. Hope this helps, Hamish

[tomr]

TheHitMaker; yes V=IR and W = I^2R (or I*I*R) - but only on d.c. systems, there's a little more to it on a.c. I is proportional to v, not inverse for exactly THM's reasons. The bit about transformer losses is pretty irrelevant for domestic uses to be fair, and Hamish, not wanting to go Spellmaster on you, it's rms.

If the question was 'If I use low voltage lighting will my consumption be less?' then no - if you want 60W of lighting the current will change according to the voltage of the system and a 12v 60W lamp will consume the same as a 240v 60W lamp.

If the question is 'My [240v] supply has dropped, will my consumption rise or fall?' your consumption will probably fall, as Hamish states the lights will be dimmer. If you have a washing machine you may find that your motor gets damaged because it still has the same 'work to do' and will try to take more current to accomodate for the lower voltage and will therefore run hot - the current in a motor is down to more than just resistance.

[Eddiecurrent]

I hope you're all talking about purely resitive loads and not those with inductance and capacitance involved. Also the UK voltage may be officially 230v/400v but in truth it is 240v and always will be ( the % tolerances will see to that)